mirror of
https://git.postgresql.org/git/postgresql.git
synced 2024-08-20 08:23:22 +02:00
As the buffer could now be a lot larger than before, and copying it could thus be a lot more expensive than before, use strcpy instead of memcpy to copy the query string, as was already suggested in comments. Also, only copy the PgBackendStatus struct and string if the slot is in use. Patch by Thomas Lee, with some changes by me.
5275 lines
218 KiB
Plaintext
5275 lines
218 KiB
Plaintext
<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.181 2008/06/30 10:58:47 heikki Exp $ -->
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<chapter Id="runtime-config">
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<title>Server Configuration</title>
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<indexterm>
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<primary>configuration</primary>
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<secondary>of the server</secondary>
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</indexterm>
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<para>
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There are many configuration parameters that affect the behavior of
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the database system. In the first section of this chapter, we
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describe how to set configuration parameters. The subsequent sections
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discuss each parameter in detail.
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</para>
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<sect1 id="config-setting">
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<title>Setting Parameters</title>
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<para>
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All parameter names are case-insensitive. Every parameter takes a
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value of one of four types: Boolean, integer, floating point,
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or string. Boolean values can be written as <literal>ON</literal>,
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<literal>OFF</literal>, <literal>TRUE</literal>,
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<literal>FALSE</literal>, <literal>YES</literal>,
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<literal>NO</literal>, <literal>1</literal>, <literal>0</literal>
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(all case-insensitive) or any unambiguous prefix of these.
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</para>
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<para>
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Some settings specify a memory or time value. Each of these has an
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implicit unit, which is either kilobytes, blocks (typically eight
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kilobytes), milliseconds, seconds, or minutes. Default units can be
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queried by referencing <literal>pg_settings.unit</>. For convenience,
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a different unit can also be specified explicitly. Valid memory units
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are <literal>kB</literal> (kilobytes), <literal>MB</literal>
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(megabytes), and <literal>GB</literal> (gigabytes); valid time units
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are <literal>ms</literal> (milliseconds), <literal>s</literal>
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(seconds), <literal>min</literal> (minutes), <literal>h</literal>
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(hours), and <literal>d</literal> (days). Note that the multiplier
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for memory units is 1024, not 1000.
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</para>
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<para>
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One way to set these parameters is to edit the file
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<filename>postgresql.conf</><indexterm><primary>postgresql.conf</></>,
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which is normally kept in the data directory. (<application>initdb</>
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installs a default copy there.) An example of what this file might look
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like is:
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<programlisting>
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# This is a comment
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log_connections = yes
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log_destination = 'syslog'
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search_path = '"$user", public'
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shared_buffers = 128MB
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</programlisting>
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One parameter is specified per line. The equal sign between name and
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value is optional. Whitespace is insignificant and blank lines are
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ignored. Hash marks (<literal>#</literal>) introduce comments
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anywhere. Parameter values that are not simple identifiers or
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numbers must be single-quoted. To embed a single quote in a parameter
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value, write either two quotes (preferred) or backslash-quote.
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</para>
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<para>
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<indexterm>
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<primary><literal>include</></primary>
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<secondary>in configuration file</secondary>
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</indexterm>
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In addition to parameter settings, the <filename>postgresql.conf</>
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file can contain <firstterm>include directives</>, which specify
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another file to read and process as if it were inserted into the
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configuration file at this point. Include directives simply look like:
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<programlisting>
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include 'filename'
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</programlisting>
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If the file name is not an absolute path, it is taken as relative to
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the directory containing the referencing configuration file.
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Inclusions can be nested.
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</para>
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<para>
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<indexterm>
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<primary>SIGHUP</primary>
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</indexterm>
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The configuration file is reread whenever the main server process receives a
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<systemitem>SIGHUP</> signal (which is most easily sent by means
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of <literal>pg_ctl reload</>). The main server process
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also propagates this signal to all currently running server
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processes so that existing sessions also get the new
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value. Alternatively, you can send the signal to a single server
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process directly. Some parameters can only be set at server start;
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any changes to their entries in the configuration file will be ignored
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until the server is restarted.
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</para>
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<para>
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A second way to set these configuration parameters is to give them
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as a command-line option to the <command>postgres</command> command, such as:
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<programlisting>
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postgres -c log_connections=yes -c log_destination='syslog'
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</programlisting>
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Command-line options override any conflicting settings in
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<filename>postgresql.conf</filename>. Note that this means you won't
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be able to change the value on-the-fly by editing
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<filename>postgresql.conf</filename>, so while the command-line
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method might be convenient, it can cost you flexibility later.
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</para>
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<para>
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Occasionally it is useful to give a command line option to
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one particular session only. The environment variable
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<envar>PGOPTIONS</envar> can be used for this purpose on the
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client side:
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<programlisting>
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env PGOPTIONS='-c geqo=off' psql
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</programlisting>
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(This works for any <application>libpq</>-based client application, not
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just <application>psql</application>.) Note that this won't work for
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parameters that are fixed when the server is started or that must be
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specified in <filename>postgresql.conf</filename>.
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</para>
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<para>
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Furthermore, it is possible to assign a set of parameter settings to
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a user or a database. Whenever a session is started, the default
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settings for the user and database involved are loaded. The
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commands <xref linkend="sql-alteruser" endterm="sql-alteruser-title">
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and <xref linkend="sql-alterdatabase" endterm="sql-alterdatabase-title">,
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respectively, are used to configure these settings. Per-database
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settings override anything received from the
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<command>postgres</command> command-line or the configuration
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file, and in turn are overridden by per-user settings; both are
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overridden by per-session settings.
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</para>
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<para>
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Some parameters can be changed in individual <acronym>SQL</acronym>
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sessions with the <xref linkend="SQL-SET" endterm="SQL-SET-title">
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command, for example:
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<screen>
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SET ENABLE_SEQSCAN TO OFF;
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</screen>
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If <command>SET</> is allowed, it overrides all other sources of
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values for the parameter. Some parameters cannot be changed via
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<command>SET</command>: for example, if they control behavior that
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cannot be changed without restarting the entire
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<productname>PostgreSQL</productname> server. Also, some parameters can
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be modified via <command>SET</command> or <command>ALTER</> by superusers,
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but not by ordinary users.
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</para>
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<para>
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The <xref linkend="SQL-SHOW" endterm="SQL-SHOW-title">
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command allows inspection of the current values of all parameters.
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</para>
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<para>
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The virtual table <structname>pg_settings</structname>
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(described in <xref linkend="view-pg-settings">) also allows
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displaying and updating session run-time parameters. It is equivalent
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to <command>SHOW</> and <command>SET</>, but can be more convenient
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to use because it can be joined with other tables, or selected from using
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any desired selection condition. It also contains more information about
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what values are allowed for the parameters.
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</para>
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</sect1>
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<sect1 id="runtime-config-file-locations">
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<title>File Locations</title>
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<para>
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In addition to the <filename>postgresql.conf</filename> file
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already mentioned, <productname>PostgreSQL</productname> uses
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two other manually-edited configuration files, which control
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client authentication (their use is discussed in <xref
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linkend="client-authentication">). By default, all three
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configuration files are stored in the database cluster's data
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directory. The parameters described in this section allow the
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configuration files to be placed elsewhere. (Doing so can ease
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administration. In particular it is often easier to ensure that
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the configuration files are properly backed-up when they are
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kept separate.)
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</para>
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<variablelist>
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<varlistentry id="guc-data-directory" xreflabel="data_directory">
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<term><varname>data_directory</varname> (<type>string</type>)</term>
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<indexterm>
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<primary><varname>data_directory</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Specifies the directory to use for data storage.
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This parameter can only be set at server start.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-config-file" xreflabel="config_file">
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<term><varname>config_file</varname> (<type>string</type>)</term>
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<indexterm>
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<primary><varname>config_file</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Specifies the main server configuration file
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(customarily called <filename>postgresql.conf</>).
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This parameter can only be set on the <command>postgres</command> command line.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-hba-file" xreflabel="hba_file">
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<term><varname>hba_file</varname> (<type>string</type>)</term>
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<indexterm>
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<primary><varname>hba_file</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Specifies the configuration file for host-based authentication
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(customarily called <filename>pg_hba.conf</>).
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This parameter can only be set at server start.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-ident-file" xreflabel="ident_file">
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<term><varname>ident_file</varname> (<type>string</type>)</term>
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<indexterm>
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<primary><varname>ident_file</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Specifies the configuration file for
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<application>ident</> authentication
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(customarily called <filename>pg_ident.conf</>).
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This parameter can only be set at server start.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-external-pid-file" xreflabel="external_pid_file">
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<term><varname>external_pid_file</varname> (<type>string</type>)</term>
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<indexterm>
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<primary><varname>external_pid_file</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Specifies the name of an additional process-id (PID) file that the
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server should create for use by server administration programs.
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This parameter can only be set at server start.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>
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In a default installation, none of the above parameters are set
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explicitly. Instead, the
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data directory is specified by the <option>-D</option> command-line
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option or the <envar>PGDATA</envar> environment variable, and the
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configuration files are all found within the data directory.
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</para>
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<para>
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If you wish to keep the configuration files elsewhere than the
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data directory, the <command>postgres</command> <option>-D</option>
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command-line option or <envar>PGDATA</envar> environment variable
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must point to the directory containing the configuration files,
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and the <varname>data_directory</> parameter must be set in
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<filename>postgresql.conf</filename> (or on the command line) to show
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where the data directory is actually located. Notice that
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<varname>data_directory</> overrides <option>-D</option> and
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<envar>PGDATA</envar> for the location
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of the data directory, but not for the location of the configuration
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files.
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</para>
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<para>
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If you wish, you can specify the configuration file names and locations
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individually using the parameters <varname>config_file</>,
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<varname>hba_file</> and/or <varname>ident_file</>.
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<varname>config_file</> can only be specified on the
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<command>postgres</command> command line, but the others can be
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set within the main configuration file. If all three parameters plus
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<varname>data_directory</> are explicitly set, then it is not necessary
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to specify <option>-D</option> or <envar>PGDATA</envar>.
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</para>
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<para>
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When setting any of these parameters, a relative path will be interpreted
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with respect to the directory in which <command>postgres</command>
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is started.
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</para>
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</sect1>
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<sect1 id="runtime-config-connection">
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<title>Connections and Authentication</title>
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<sect2 id="runtime-config-connection-settings">
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<title>Connection Settings</title>
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<variablelist>
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<varlistentry id="guc-listen-addresses" xreflabel="listen_addresses">
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<term><varname>listen_addresses</varname> (<type>string</type>)</term>
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<indexterm>
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<primary><varname>listen_addresses</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Specifies the TCP/IP address(es) on which the server is
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to listen for connections from client applications.
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The value takes the form of a comma-separated list of host names
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and/or numeric IP addresses. The special entry <literal>*</>
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corresponds to all available IP interfaces.
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If the list is empty, the server does not listen on any IP interface
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at all, in which case only Unix-domain sockets can be used to connect
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to it.
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The default value is <systemitem class="systemname">localhost</>,
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which allows only local <quote>loopback</> connections to be made.
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This parameter can only be set at server start.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-port" xreflabel="port">
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<term><varname>port</varname> (<type>integer</type>)</term>
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<indexterm>
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<primary><varname>port</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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The TCP port the server listens on; 5432 by default. Note that the
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same port number is used for all IP addresses the server listens on.
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This parameter can only be set at server start.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-max-connections" xreflabel="max_connections">
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<term><varname>max_connections</varname> (<type>integer</type>)</term>
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<indexterm>
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<primary><varname>max_connections</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Determines the maximum number of concurrent connections to the
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database server. The default is typically 100 connections, but
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might be less if your kernel settings will not support it (as
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determined during <application>initdb</>). This parameter can
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only be set at server start.
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</para>
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<para>
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Increasing this parameter might cause <productname>PostgreSQL</>
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to request more <systemitem class="osname">System V</> shared
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memory or semaphores than your operating system's default configuration
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allows. See <xref linkend="sysvipc"> for information on how to
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adjust those parameters, if necessary.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-superuser-reserved-connections"
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xreflabel="superuser_reserved_connections">
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<term><varname>superuser_reserved_connections</varname>
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(<type>integer</type>)</term>
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<indexterm>
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<primary><varname>superuser_reserved_connections</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Determines the number of connection <quote>slots</quote> that
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are reserved for connections by <productname>PostgreSQL</>
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superusers. At most <xref linkend="guc-max-connections">
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connections can ever be active simultaneously. Whenever the
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number of active concurrent connections is at least
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<varname>max_connections</> minus
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<varname>superuser_reserved_connections</varname>, new
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connections will be accepted only for superusers.
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</para>
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<para>
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The default value is three connections. The value must be less
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than the value of <varname>max_connections</varname>. This
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parameter can only be set at server start.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-unix-socket-directory" xreflabel="unix_socket_directory">
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<term><varname>unix_socket_directory</varname> (<type>string</type>)</term>
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<indexterm>
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<primary><varname>unix_socket_directory</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Specifies the directory of the Unix-domain socket on which the
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server is to listen for
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connections from client applications. The default is normally
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<filename>/tmp</filename>, but can be changed at build time.
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This parameter can only be set at server start.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-unix-socket-group" xreflabel="unix_socket_group">
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<term><varname>unix_socket_group</varname> (<type>string</type>)</term>
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<indexterm>
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<primary><varname>unix_socket_group</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Sets the owning group of the Unix-domain socket. (The owning
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user of the socket is always the user that starts the
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server.) In combination with the parameter
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<varname>unix_socket_permissions</varname> this can be used as
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an additional access control mechanism for Unix-domain connections.
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By default this is the empty string, which selects the default
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group for the current user. This parameter can only be set at
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server start.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-unix-socket-permissions" xreflabel="unix_socket_permissions">
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<term><varname>unix_socket_permissions</varname> (<type>integer</type>)</term>
|
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<indexterm>
|
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<primary><varname>unix_socket_permissions</> configuration parameter</primary>
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</indexterm>
|
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<listitem>
|
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<para>
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Sets the access permissions of the Unix-domain socket. Unix-domain
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sockets use the usual Unix file system permission set.
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|
The parameter value is expected to be a numeric mode
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|
specification in the form accepted by the
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<function>chmod</function> and <function>umask</function>
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system calls. (To use the customary octal format the number
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must start with a <literal>0</literal> (zero).)
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</para>
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<para>
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The default permissions are <literal>0777</literal>, meaning
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anyone can connect. Reasonable alternatives are
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<literal>0770</literal> (only user and group, see also
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<varname>unix_socket_group</varname>) and <literal>0700</literal>
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(only user). (Note that for a Unix-domain socket, only write
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permission matters and so there is no point in setting or revoking
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read or execute permissions.)
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</para>
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<para>
|
|
This access control mechanism is independent of the one
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|
described in <xref linkend="client-authentication">.
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|
</para>
|
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|
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<para>
|
|
This parameter can only be set at server start.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-bonjour-name" xreflabel="bonjour_name">
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<term><varname>bonjour_name</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>bonjour_name</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the <productname>Bonjour</productname> broadcast
|
|
name. The computer name is used if this parameter is set to the
|
|
empty string <literal>''</> (which is the default). This parameter is
|
|
ignored if the server was not compiled with
|
|
<productname>Bonjour</productname> support.
|
|
This parameter can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-tcp-keepalives-idle" xreflabel="tcp_keepalives_idle">
|
|
<term><varname>tcp_keepalives_idle</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>tcp_keepalives_idle</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
On systems that support the <symbol>TCP_KEEPIDLE</symbol> socket option, specifies the
|
|
number of seconds between sending keepalives on an otherwise idle
|
|
connection. A value of zero uses the system default. If <symbol>TCP_KEEPIDLE</symbol> is
|
|
not supported, this parameter must be zero. This parameter is ignored for
|
|
connections made via a Unix-domain socket.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-tcp-keepalives-interval" xreflabel="tcp_keepalives_interval">
|
|
<term><varname>tcp_keepalives_interval</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>tcp_keepalives_interval</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
On systems that support the <symbol>TCP_KEEPINTVL</symbol> socket option, specifies how
|
|
long, in seconds, to wait for a response to a keepalive before
|
|
retransmitting. A value of zero uses the system default. If <symbol>TCP_KEEPINTVL</symbol>
|
|
is not supported, this parameter must be zero. This parameter is ignored
|
|
for connections made via a Unix-domain socket.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-tcp-keepalives-count" xreflabel="tcp_keepalives_count">
|
|
<term><varname>tcp_keepalives_count</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>tcp_keepalives_count</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
On systems that support the <symbol>TCP_KEEPCNT</symbol> socket option, specifies how
|
|
many keepalives can be lost before the connection is considered dead.
|
|
A value of zero uses the system default. If <symbol>TCP_KEEPCNT</symbol> is not
|
|
supported, this parameter must be zero. This parameter is ignored
|
|
for connections made via a Unix-domain socket.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
<sect2 id="runtime-config-connection-security">
|
|
<title>Security and Authentication</title>
|
|
|
|
<variablelist>
|
|
<varlistentry id="guc-authentication-timeout" xreflabel="authentication_timeout">
|
|
<term><varname>authentication_timeout</varname> (<type>integer</type>)</term>
|
|
<indexterm><primary>timeout</><secondary>client authentication</></indexterm>
|
|
<indexterm><primary>client authentication</><secondary>timeout during</></indexterm>
|
|
<indexterm>
|
|
<primary><varname>authentication_timeout</> configuration parameter</primary>
|
|
</indexterm>
|
|
|
|
<listitem>
|
|
<para>
|
|
Maximum time to complete client authentication, in seconds. If a
|
|
would-be client has not completed the authentication protocol in
|
|
this much time, the server breaks the connection. This prevents
|
|
hung clients from occupying a connection indefinitely.
|
|
The default is one minute (<literal>1m</>).
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-ssl" xreflabel="ssl">
|
|
<term><varname>ssl</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>ssl</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables <acronym>SSL</> connections. Please read
|
|
<xref linkend="ssl-tcp"> before using this. The default
|
|
is <literal>off</>. This parameter can only be set at server
|
|
start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-ssl-ciphers" xreflabel="ssl_ciphers">
|
|
<term><varname>ssl_ciphers</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>ssl_ciphers</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies a list of <acronym>SSL</> ciphers that are allowed to be
|
|
used on secure connections. See the <application>openssl</>
|
|
manual page for a list of supported ciphers.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-password-encryption" xreflabel="password_encryption">
|
|
<term><varname>password_encryption</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>password_encryption</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When a password is specified in <xref
|
|
linkend="sql-createuser" endterm="sql-createuser-title"> or
|
|
<xref linkend="sql-alteruser" endterm="sql-alteruser-title">
|
|
without writing either <literal>ENCRYPTED</> or
|
|
<literal>UNENCRYPTED</>, this parameter determines whether the
|
|
password is to be encrypted. The default is <literal>on</>
|
|
(encrypt the password).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-krb-realm" xreflabel="krb_realm">
|
|
<term><varname>krb_realm</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>krb_realm</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the realm to match Kerberos, GSSAPI and SSPI user names against.
|
|
See <xref linkend="kerberos-auth">, <xref linkend="gssapi-auth"> or
|
|
<xref linkend="sspi-auth"> for details. This parameter can only be
|
|
set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-krb-server-keyfile" xreflabel="krb_server_keyfile">
|
|
<term><varname>krb_server_keyfile</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>krb_server_keyfile</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the location of the Kerberos server key file. See
|
|
<xref linkend="kerberos-auth"> or <xref linkend="gssapi-auth">
|
|
for details. This parameter can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-krb-srvname" xreflabel="krb_srvname">
|
|
<term><varname>krb_srvname</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>krb_srvname</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the Kerberos service name. See <xref linkend="kerberos-auth">
|
|
for details. This parameter can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-krb-server-hostname" xreflabel="krb_server_hostname">
|
|
<term><varname>krb_server_hostname</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>krb_server_hostname</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the host name part of the service principal.
|
|
This, combined with <varname>krb_srvname</>, is used to generate
|
|
the complete service principal, that is
|
|
<varname>krb_srvname</><literal>/</><varname>krb_server_hostname</><literal>@</>REALM.
|
|
If not set, the default is the server host name. See <xref linkend="kerberos-auth">
|
|
for details. This parameter can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-krb-caseins-users" xreflabel="krb_caseins_users">
|
|
<term><varname>krb_caseins_users</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>krb_caseins_users</varname> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets whether Kerberos and GSSAPI user names should be treated
|
|
case-insensitively.
|
|
The default is <literal>off</> (case sensitive). This parameter
|
|
can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-db-user-namespace" xreflabel="db_user_namespace">
|
|
<term><varname>db_user_namespace</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>db_user_namespace</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This parameter enables per-database user names. It is off by default.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
|
|
<para>
|
|
If this is on, you should create users as <literal>username@dbname</>.
|
|
When <literal>username</> is passed by a connecting client,
|
|
<literal>@</> and the database name are appended to the user
|
|
name and that database-specific user name is looked up by the
|
|
server. Note that when you create users with names containing
|
|
<literal>@</> within the SQL environment, you will need to
|
|
quote the user name.
|
|
</para>
|
|
|
|
<para>
|
|
With this parameter enabled, you can still create ordinary global
|
|
users. Simply append <literal>@</> when specifying the user
|
|
name in the client. The <literal>@</> will be stripped off
|
|
before the user name is looked up by the server.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
This feature is intended as a temporary measure until a
|
|
complete solution is found. At that time, this option will
|
|
be removed.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-resource">
|
|
<title>Resource Consumption</title>
|
|
|
|
<sect2 id="runtime-config-resource-memory">
|
|
<title>Memory</title>
|
|
|
|
<variablelist>
|
|
<varlistentry id="guc-shared-buffers" xreflabel="shared_buffers">
|
|
<term><varname>shared_buffers</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>shared_buffers</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the amount of memory the database server uses for shared
|
|
memory buffers. The default is typically 32 megabytes
|
|
(<literal>32MB</>), but might be less if your kernel settings will
|
|
not support it (as determined during <application>initdb</>).
|
|
This setting must be at least 128 kilobytes. (Non-default
|
|
values of <symbol>BLCKSZ</symbol> change the minimum.) However,
|
|
settings significantly higher than the minimum are usually needed
|
|
for good performance. Several tens of megabytes are recommended
|
|
for production installations. This parameter can only be set at
|
|
server start.
|
|
</para>
|
|
|
|
<para>
|
|
Increasing this parameter might cause <productname>PostgreSQL</>
|
|
to request more <systemitem class="osname">System V</> shared
|
|
memory than your operating system's default configuration
|
|
allows. See <xref linkend="sysvipc"> for information on how to
|
|
adjust those parameters, if necessary.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-temp-buffers" xreflabel="temp_buffers">
|
|
<term><varname>temp_buffers</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>temp_buffers</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the maximum number of temporary buffers used by each database
|
|
session. These are session-local buffers used only for access to
|
|
temporary tables. The default is eight megabytes
|
|
(<literal>8MB</>). The setting can be changed within individual
|
|
sessions, but only up until the first use of temporary tables
|
|
within a session; subsequent attempts to change the value will
|
|
have no effect on that session.
|
|
</para>
|
|
|
|
<para>
|
|
A session will allocate temporary buffers as needed up to the limit
|
|
given by <varname>temp_buffers</>. The cost of setting a large
|
|
value in sessions that do not actually need a lot of temporary
|
|
buffers is only a buffer descriptor, or about 64 bytes, per
|
|
increment in <varname>temp_buffers</>. However if a buffer is
|
|
actually used an additional 8192 bytes will be consumed for it
|
|
(or in general, <symbol>BLCKSZ</symbol> bytes).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-max-prepared-transactions" xreflabel="max_prepared_transactions">
|
|
<term><varname>max_prepared_transactions</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>max_prepared_transactions</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the maximum number of transactions that can be in the
|
|
<quote>prepared</> state simultaneously (see <xref
|
|
linkend="sql-prepare-transaction"
|
|
endterm="sql-prepare-transaction-title">).
|
|
Setting this parameter to zero disables the prepared-transaction
|
|
feature.
|
|
The default is five transactions.
|
|
This parameter can only be set at server start.
|
|
</para>
|
|
|
|
<para>
|
|
If you are not using prepared transactions, this parameter may as
|
|
well be set to zero. If you are using them, you will probably
|
|
want <varname>max_prepared_transactions</varname> to be at least
|
|
as large as <xref linkend="guc-max-connections">, to avoid unwanted
|
|
failures at the prepare step.
|
|
</para>
|
|
|
|
<para>
|
|
Increasing this parameter might cause <productname>PostgreSQL</>
|
|
to request more <systemitem class="osname">System V</> shared
|
|
memory than your operating system's default configuration
|
|
allows. See <xref linkend="sysvipc"> for information on how to
|
|
adjust those parameters, if necessary.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-work-mem" xreflabel="work_mem">
|
|
<term><varname>work_mem</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>work_mem</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the amount of memory to be used by internal sort operations
|
|
and hash tables before switching to temporary disk files. The value
|
|
defaults to one megabyte (<literal>1MB</>).
|
|
Note that for a complex query, several sort or hash operations might be
|
|
running in parallel; each one will be allowed to use as much memory
|
|
as this value specifies before it starts to put data into temporary
|
|
files. Also, several running sessions could be doing such operations
|
|
concurrently. So the total memory used could be many
|
|
times the value of <varname>work_mem</varname>; it is necessary to
|
|
keep this fact in mind when choosing the value. Sort operations are
|
|
used for <literal>ORDER BY</>, <literal>DISTINCT</>, and
|
|
merge joins.
|
|
Hash tables are used in hash joins, hash-based aggregation, and
|
|
hash-based processing of <literal>IN</> subqueries.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-maintenance-work-mem" xreflabel="maintenance_work_mem">
|
|
<term><varname>maintenance_work_mem</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>maintenance_work_mem</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the maximum amount of memory to be used in maintenance
|
|
operations, such as <command>VACUUM</command>, <command>CREATE
|
|
INDEX</>, and <command>ALTER TABLE ADD FOREIGN KEY</>. It defaults
|
|
to 16 megabytes (<literal>16MB</>). Since only one of these
|
|
operations can be executed at a time by a database session, and
|
|
an installation normally doesn't have many of them running
|
|
concurrently, it's safe to set this value significantly larger
|
|
than <varname>work_mem</varname>. Larger settings might improve
|
|
performance for vacuuming and for restoring database dumps.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-max-stack-depth" xreflabel="max_stack_depth">
|
|
<term><varname>max_stack_depth</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>max_stack_depth</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the maximum safe depth of the server's execution stack.
|
|
The ideal setting for this parameter is the actual stack size limit
|
|
enforced by the kernel (as set by <literal>ulimit -s</> or local
|
|
equivalent), less a safety margin of a megabyte or so. The safety
|
|
margin is needed because the stack depth is not checked in every
|
|
routine in the server, but only in key potentially-recursive routines
|
|
such as expression evaluation. The default setting is two
|
|
megabytes (<literal>2MB</>), which is conservatively small and
|
|
unlikely to risk crashes. However, it might be too small to allow
|
|
execution of complex functions. Only superusers can change this
|
|
setting.
|
|
</para>
|
|
|
|
<para>
|
|
Setting <varname>max_stack_depth</> higher than
|
|
the actual kernel limit will mean that a runaway recursive function
|
|
can crash an individual backend process. On platforms where
|
|
<productname>PostgreSQL</productname> can determine the kernel limit,
|
|
it will not let you set this variable to an unsafe value. However,
|
|
not all platforms provide the information, so caution is recommended
|
|
in selecting a value.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
<sect2 id="runtime-config-resource-fsm">
|
|
<title>Free Space Map</title>
|
|
|
|
<indexterm>
|
|
<primary>free space map</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
These parameters control the size of the shared <firstterm>free space
|
|
map</> (<acronym>FSM</>), which tracks the locations of unused space in the database.
|
|
An undersized free space map can cause the database to consume
|
|
increasing amounts of disk space over time, because free space that
|
|
is not in the map cannot be re-used; instead <productname>PostgreSQL</>
|
|
will request more disk space from the operating system when it needs
|
|
to store new data.
|
|
The last few lines displayed by a database-wide <command>VACUUM VERBOSE</>
|
|
command can help in determining if the current settings are adequate.
|
|
A <literal>NOTICE</> message is also printed during such an operation
|
|
if the current settings are too low.
|
|
</para>
|
|
|
|
<para>
|
|
Increasing these parameters might cause <productname>PostgreSQL</>
|
|
to request more <systemitem class="osname">System V</> shared
|
|
memory than your operating system's default configuration
|
|
allows. See <xref linkend="sysvipc"> for information on how to
|
|
adjust those parameters, if necessary.
|
|
</para>
|
|
|
|
<variablelist>
|
|
<varlistentry id="guc-max-fsm-pages" xreflabel="max_fsm_pages">
|
|
<term><varname>max_fsm_pages</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>max_fsm_pages</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the maximum number of disk pages for which free space will
|
|
be tracked in the shared free-space map. Six bytes of shared memory
|
|
are consumed for each page slot. This setting must be at least
|
|
16 * <varname>max_fsm_relations</varname>. The default is chosen
|
|
by <application>initdb</> depending on the amount of available memory,
|
|
and can range from 20k to 200k pages.
|
|
This parameter can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-max-fsm-relations" xreflabel="max_fsm_relations">
|
|
<term><varname>max_fsm_relations</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>max_fsm_relations</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the maximum number of relations (tables and indexes) for which
|
|
free space will be tracked in the shared free-space map. Roughly
|
|
seventy bytes of shared memory are consumed for each slot.
|
|
The default is one thousand relations.
|
|
This parameter can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
|
|
<note>
|
|
<para>
|
|
See the <xref linkend="sql-vacuum" endterm="sql-vacuum-title">
|
|
command for information on setting this parameter.
|
|
</para>
|
|
</note>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="runtime-config-resource-kernel">
|
|
<title>Kernel Resource Usage</title>
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-max-files-per-process" xreflabel="max_files_per_process">
|
|
<term><varname>max_files_per_process</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>max_files_per_process</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the maximum number of simultaneously open files allowed to each
|
|
server subprocess. The default is one thousand files. If the kernel is enforcing
|
|
a safe per-process limit, you don't need to worry about this setting.
|
|
But on some platforms (notably, most BSD systems), the kernel will
|
|
allow individual processes to open many more files than the system
|
|
can really support when a large number of processes all try to open
|
|
that many files. If you find yourself seeing <quote>Too many open
|
|
files</> failures, try reducing this setting.
|
|
This parameter can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-shared-preload-libraries" xreflabel="shared_preload_libraries">
|
|
<term><varname>shared_preload_libraries</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>shared_preload_libraries</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This variable specifies one or more shared libraries that are
|
|
to be preloaded at server start. If more than one library is to be
|
|
loaded, separate their names with commas. For example,
|
|
<literal>'$libdir/mylib'</literal> would cause
|
|
<literal>mylib.so</> (or on some platforms,
|
|
<literal>mylib.sl</>) to be preloaded from the installation's
|
|
standard library directory.
|
|
This parameter can only be set at server start.
|
|
</para>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> procedural language
|
|
libraries can be preloaded in this way, typically by using the
|
|
syntax <literal>'$libdir/plXXX'</literal> where
|
|
<literal>XXX</literal> is <literal>pgsql</>, <literal>perl</>,
|
|
<literal>tcl</>, or <literal>python</>.
|
|
</para>
|
|
|
|
<para>
|
|
By preloading a shared library, the library startup time is avoided
|
|
when the library is first used. However, the time to start each new
|
|
server process might increase slightly, even if that process never
|
|
uses the library. So this parameter is recommended only for
|
|
libraries that will be used in most sessions.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
On Windows hosts, preloading a library at server start will not reduce
|
|
the time required to start each new server process; each server process
|
|
will re-load all preload libraries. However, <varname>shared_preload_libraries
|
|
</varname> is still useful on Windows hosts because some shared libraries may
|
|
need to perform certain operations that only take place at postmaster start
|
|
(for example, a shared library may need to reserve lightweight locks
|
|
or shared memory and you can't do that after the postmaster has started).
|
|
</para>
|
|
</note>
|
|
<para>
|
|
If a specified library is not found,
|
|
the server will fail to start.
|
|
</para>
|
|
|
|
<para>
|
|
Every PostgreSQL-supported library has a <quote>magic
|
|
block</> that is checked to guarantee compatibility.
|
|
For this reason, non-PostgreSQL libraries cannot be
|
|
loaded in this way.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
<sect2 id="runtime-config-resource-vacuum-cost">
|
|
<title id="runtime-config-resource-vacuum-cost-title">
|
|
Cost-Based Vacuum Delay
|
|
</title>
|
|
|
|
<para>
|
|
During the execution of <xref linkend="sql-vacuum"
|
|
endterm="sql-vacuum-title"> and <xref linkend="sql-analyze"
|
|
endterm="sql-analyze-title"> commands, the system maintains an
|
|
internal counter that keeps track of the estimated cost of the
|
|
various I/O operations that are performed. When the accumulated
|
|
cost reaches a limit (specified by
|
|
<varname>vacuum_cost_limit</varname>), the process performing
|
|
the operation will sleep for a while (specified by
|
|
<varname>vacuum_cost_delay</varname>). Then it will reset the
|
|
counter and continue execution.
|
|
</para>
|
|
|
|
<para>
|
|
The intent of this feature is to allow administrators to reduce
|
|
the I/O impact of these commands on concurrent database
|
|
activity. There are many situations in which it is not very
|
|
important that maintenance commands like
|
|
<command>VACUUM</command> and <command>ANALYZE</command> finish
|
|
quickly; however, it is usually very important that these
|
|
commands do not significantly interfere with the ability of the
|
|
system to perform other database operations. Cost-based vacuum
|
|
delay provides a way for administrators to achieve this.
|
|
</para>
|
|
|
|
<para>
|
|
This feature is disabled by default. To enable it, set the
|
|
<varname>vacuum_cost_delay</varname> variable to a nonzero
|
|
value.
|
|
</para>
|
|
|
|
<variablelist>
|
|
<varlistentry id="guc-vacuum-cost-delay" xreflabel="vacuum_cost_delay">
|
|
<term><varname>vacuum_cost_delay</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>vacuum_cost_delay</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The length of time, in milliseconds, that the process will sleep
|
|
when the cost limit has been exceeded.
|
|
The default value is zero, which disables the cost-based vacuum
|
|
delay feature. Positive values enable cost-based vacuuming.
|
|
Note that on many systems, the effective resolution
|
|
of sleep delays is 10 milliseconds; setting
|
|
<varname>vacuum_cost_delay</varname> to a value that is
|
|
not a multiple of 10 might have the same results as setting it
|
|
to the next higher multiple of 10.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-vacuum-cost-page-hit" xreflabel="vacuum_cost_page_hit">
|
|
<term><varname>vacuum_cost_page_hit</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>vacuum_cost_page_hit</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The estimated cost for vacuuming a buffer found in the shared buffer
|
|
cache. It represents the cost to lock the buffer pool, lookup
|
|
the shared hash table and scan the content of the page. The
|
|
default value is one.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-vacuum-cost-page-miss" xreflabel="vacuum_cost_page_miss">
|
|
<term><varname>vacuum_cost_page_miss</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>vacuum_cost_page_miss</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The estimated cost for vacuuming a buffer that has to be read from
|
|
disk. This represents the effort to lock the buffer pool,
|
|
lookup the shared hash table, read the desired block in from
|
|
the disk and scan its content. The default value is 10.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-vacuum-cost-page-dirty" xreflabel="vacuum_cost_page_dirty">
|
|
<term><varname>vacuum_cost_page_dirty</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>vacuum_cost_page_dirty</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The estimated cost charged when vacuum modifies a block that was
|
|
previously clean. It represents the extra I/O required to
|
|
flush the dirty block out to disk again. The default value is
|
|
20.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-vacuum-cost-limit" xreflabel="vacuum_cost_limit">
|
|
<term><varname>vacuum_cost_limit</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>vacuum_cost_limit</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The accumulated cost that will cause the vacuuming process to sleep.
|
|
The default value is 200.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<note>
|
|
<para>
|
|
There are certain operations that hold critical locks and should
|
|
therefore complete as quickly as possible. Cost-based vacuum
|
|
delays do not occur during such operations. Therefore it is
|
|
possible that the cost accumulates far higher than the specified
|
|
limit. To avoid uselessly long delays in such cases, the actual
|
|
delay is calculated as <varname>vacuum_cost_delay</varname> *
|
|
<varname>accumulated_balance</varname> /
|
|
<varname>vacuum_cost_limit</varname> with a maximum of
|
|
<varname>vacuum_cost_delay</varname> * 4.
|
|
</para>
|
|
</note>
|
|
</sect2>
|
|
|
|
<sect2 id="runtime-config-resource-background-writer">
|
|
<title>Background Writer</title>
|
|
|
|
<para>
|
|
There is a separate server
|
|
process called the <firstterm>background writer</>, whose function
|
|
is to issue writes of <quote>dirty</> shared buffers. The intent is
|
|
that server processes handling user queries should seldom or never have
|
|
to wait for a write to occur, because the background writer will do it.
|
|
However there is a net overall
|
|
increase in I/O load, because a repeatedly-dirtied page might
|
|
otherwise be written only once per checkpoint interval, but the
|
|
background writer might write it several times in the same interval.
|
|
The parameters discussed in this subsection can be used to
|
|
tune the behavior for local needs.
|
|
</para>
|
|
|
|
<variablelist>
|
|
<varlistentry id="guc-bgwriter-delay" xreflabel="bgwriter_delay">
|
|
<term><varname>bgwriter_delay</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>bgwriter_delay</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the delay between activity rounds for the
|
|
background writer. In each round the writer issues writes
|
|
for some number of dirty buffers (controllable by the
|
|
following parameters). It then sleeps for <varname>bgwriter_delay</>
|
|
milliseconds, and repeats. The default value is 200 milliseconds
|
|
(<literal>200ms</>). Note that on many systems, the effective
|
|
resolution of sleep delays is 10 milliseconds; setting
|
|
<varname>bgwriter_delay</> to a value that is not a multiple of
|
|
10 might have the same results as setting it to the next higher
|
|
multiple of 10. This parameter can only be set in the
|
|
<filename>postgresql.conf</> file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-bgwriter-lru-maxpages" xreflabel="bgwriter_lru_maxpages">
|
|
<term><varname>bgwriter_lru_maxpages</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>bgwriter_lru_maxpages</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
In each round, no more than this many buffers will be written
|
|
by the background writer. Setting this to zero disables
|
|
background writing (except for checkpoint activity).
|
|
The default value is 100 buffers.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-bgwriter-lru-multiplier" xreflabel="bgwriter_lru_multiplier">
|
|
<term><varname>bgwriter_lru_multiplier</varname> (<type>floating point</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>bgwriter_lru_multiplier</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The number of dirty buffers written in each round is based on the
|
|
number of new buffers that have been needed by server processes
|
|
during recent rounds. The average recent need is multiplied by
|
|
<varname>bgwriter_lru_multiplier</> to arrive at an estimate of the
|
|
number of buffers that will be needed during the next round. Dirty
|
|
buffers are written until there are that many clean, reusable buffers
|
|
available. (However, no more than <varname>bgwriter_lru_maxpages</>
|
|
buffers will be written per round.)
|
|
Thus, a setting of 1.0 represents a <quote>just in time</> policy
|
|
of writing exactly the number of buffers predicted to be needed.
|
|
Larger values provide some cushion against spikes in demand,
|
|
while smaller values intentionally leave writes to be done by
|
|
server processes.
|
|
The default is 2.0.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>
|
|
Smaller values of <varname>bgwriter_lru_maxpages</varname> and
|
|
<varname>bgwriter_lru_multiplier</varname> reduce the extra I/O load
|
|
caused by the background writer, but make it more likely that server
|
|
processes will have to issue writes for themselves, delaying interactive
|
|
queries.
|
|
</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-wal">
|
|
<title>Write Ahead Log</title>
|
|
|
|
<para>
|
|
See also <xref linkend="wal-configuration"> for details on WAL
|
|
and checkpoint tuning.
|
|
</para>
|
|
|
|
<sect2 id="runtime-config-wal-settings">
|
|
<title>Settings</title>
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-fsync" xreflabel="fsync">
|
|
<indexterm>
|
|
<primary><varname>fsync</> configuration parameter</primary>
|
|
</indexterm>
|
|
<term><varname>fsync</varname> (<type>boolean</type>)</term>
|
|
<listitem>
|
|
<para>
|
|
If this parameter is on, the <productname>PostgreSQL</> server
|
|
will try to make sure that updates are physically written to
|
|
disk, by issuing <function>fsync()</> system calls or various
|
|
equivalent methods (see <xref linkend="guc-wal-sync-method">).
|
|
This ensures that the database cluster can recover to a
|
|
consistent state after an operating system or hardware crash.
|
|
</para>
|
|
|
|
<para>
|
|
However, using <varname>fsync</varname> results in a
|
|
performance penalty: when a transaction is committed,
|
|
<productname>PostgreSQL</productname> must wait for the
|
|
operating system to flush the write-ahead log to disk. When
|
|
<varname>fsync</varname> is disabled, the operating system is
|
|
allowed to do its best in buffering, ordering, and delaying
|
|
writes. This can result in significantly improved performance.
|
|
However, if the system crashes, the results of the last few
|
|
committed transactions might be lost in part or whole. In the
|
|
worst case, unrecoverable data corruption might occur.
|
|
(Crashes of the database software itself are <emphasis>not</>
|
|
a risk factor here. Only an operating-system-level crash
|
|
creates a risk of corruption.)
|
|
</para>
|
|
|
|
<para>
|
|
Due to the risks involved, there is no universally correct
|
|
setting for <varname>fsync</varname>. Some administrators
|
|
always disable <varname>fsync</varname>, while others only
|
|
turn it off during initial bulk data loads, where there is a clear
|
|
restart point if something goes wrong. Others
|
|
always leave <varname>fsync</varname> enabled. The default is
|
|
to enable <varname>fsync</varname>, for maximum reliability.
|
|
If you trust your operating system, your hardware, and your
|
|
utility company (or your battery backup), you can consider
|
|
disabling <varname>fsync</varname>.
|
|
</para>
|
|
|
|
<para>
|
|
In many situations, turning off <xref linkend="guc-synchronous-commit">
|
|
for noncritical transactions can provide much of the potential
|
|
performance benefit of turning off <varname>fsync</varname>, without
|
|
the attendant risks of data corruption.
|
|
</para>
|
|
|
|
<para>
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
If you turn this parameter off, also consider turning off
|
|
<xref linkend="guc-full-page-writes">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-synchronous-commit" xreflabel="synchronous_commit">
|
|
<term><varname>synchronous_commit</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>synchronous_commit</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies whether transaction commit will wait for WAL records
|
|
to be written to disk before the command returns a <quote>success</>
|
|
indication to the client. The default, and safe, setting is
|
|
<literal>on</>. When <literal>off</>, there can be a delay between
|
|
when success is reported to the client and when the transaction is
|
|
really guaranteed to be safe against a server crash. (The maximum
|
|
delay is three times <xref linkend="guc-wal-writer-delay">.) Unlike
|
|
<xref linkend="guc-fsync">, setting this parameter to <literal>off</>
|
|
does not create any risk of database inconsistency: a crash might
|
|
result in some recent allegedly-committed transactions being lost, but
|
|
the database state will be just the same as if those transactions had
|
|
been aborted cleanly. So, turning <varname>synchronous_commit</> off
|
|
can be a useful alternative when performance is more important than
|
|
exact certainty about the durability of a transaction. For more
|
|
discussion see <xref linkend="wal-async-commit">.
|
|
</para>
|
|
<para>
|
|
This parameter can be changed at any time; the behavior for any
|
|
one transaction is determined by the setting in effect when it
|
|
commits. It is therefore possible, and useful, to have some
|
|
transactions commit synchronously and others asynchronously.
|
|
For example, to make a single multi-statement transaction commit
|
|
asynchronously when the default is the opposite, issue <command>SET
|
|
LOCAL synchronous_commit TO OFF</> within the transaction.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-wal-sync-method" xreflabel="wal_sync_method">
|
|
<term><varname>wal_sync_method</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>wal_sync_method</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Method used for forcing WAL updates out to disk.
|
|
If <varname>fsync</varname> is off then this setting is irrelevant,
|
|
since updates will not be forced out at all.
|
|
Possible values are:
|
|
</para>
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
<literal>open_datasync</> (write WAL files with <function>open()</> option <symbol>O_DSYNC</>)
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>fdatasync</> (call <function>fdatasync()</> at each commit)
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>fsync_writethrough</> (call <function>fsync()</> at each commit, forcing write-through of any disk write cache)
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>fsync</> (call <function>fsync()</> at each commit)
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<literal>open_sync</> (write WAL files with <function>open()</> option <symbol>O_SYNC</>)
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
<para>
|
|
Not all of these choices are available on all platforms.
|
|
The default is the first method in the above list that is supported
|
|
by the platform.
|
|
The <literal>open_</>* options also use <literal>O_DIRECT</> if available.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-full-page-writes" xreflabel="full_page_writes">
|
|
<indexterm>
|
|
<primary><varname>full_page_writes</> configuration parameter</primary>
|
|
</indexterm>
|
|
<term><varname>full_page_writes</varname> (<type>boolean</type>)</term>
|
|
<listitem>
|
|
<para>
|
|
When this parameter is on, the <productname>PostgreSQL</> server
|
|
writes the entire content of each disk page to WAL during the
|
|
first modification of that page after a checkpoint.
|
|
This is needed because
|
|
a page write that is in process during an operating system crash might
|
|
be only partially completed, leading to an on-disk page
|
|
that contains a mix of old and new data. The row-level change data
|
|
normally stored in WAL will not be enough to completely restore
|
|
such a page during post-crash recovery. Storing the full page image
|
|
guarantees that the page can be correctly restored, but at a price
|
|
in increasing the amount of data that must be written to WAL.
|
|
(Because WAL replay always starts from a checkpoint, it is sufficient
|
|
to do this during the first change of each page after a checkpoint.
|
|
Therefore, one way to reduce the cost of full-page writes is to
|
|
increase the checkpoint interval parameters.)
|
|
</para>
|
|
|
|
<para>
|
|
Turning this parameter off speeds normal operation, but
|
|
might lead to a corrupt database after an operating system crash
|
|
or power failure. The risks are similar to turning off
|
|
<varname>fsync</>, though smaller. It might be safe to turn off
|
|
this parameter if you have hardware (such as a battery-backed disk
|
|
controller) or file-system software that reduces
|
|
the risk of partial page writes to an acceptably low level (e.g., ReiserFS 4).
|
|
</para>
|
|
|
|
<para>
|
|
Turning off this parameter does not affect use of
|
|
WAL archiving for point-in-time recovery (PITR)
|
|
(see <xref linkend="continuous-archiving">).
|
|
</para>
|
|
|
|
<para>
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
The default is <literal>on</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-wal-buffers" xreflabel="wal_buffers">
|
|
<term><varname>wal_buffers</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>wal_buffers</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The amount of memory used in shared memory for WAL data. The
|
|
default is 64 kilobytes (<literal>64kB</>). The setting need only
|
|
be large enough to hold the amount of WAL data generated by one
|
|
typical transaction, since the data is written out to disk at
|
|
every transaction commit. This parameter can only be set at server
|
|
start.
|
|
</para>
|
|
|
|
<para>
|
|
Increasing this parameter might cause <productname>PostgreSQL</>
|
|
to request more <systemitem class="osname">System V</> shared
|
|
memory than your operating system's default configuration
|
|
allows. See <xref linkend="sysvipc"> for information on how to
|
|
adjust those parameters, if necessary.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-wal-writer-delay" xreflabel="wal_writer_delay">
|
|
<term><varname>wal_writer_delay</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>wal_writer_delay</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the delay between activity rounds for the WAL writer.
|
|
In each round the writer will flush WAL to disk. It then sleeps for
|
|
<varname>wal_writer_delay</> milliseconds, and repeats. The default
|
|
value is 200 milliseconds (<literal>200ms</>). Note that on many
|
|
systems, the effective resolution of sleep delays is 10 milliseconds;
|
|
setting <varname>wal_writer_delay</> to a value that is not a multiple
|
|
of 10 might have the same results as setting it to the next higher
|
|
multiple of 10. This parameter can only be set in the
|
|
<filename>postgresql.conf</> file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-commit-delay" xreflabel="commit_delay">
|
|
<term><varname>commit_delay</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>commit_delay</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Time delay between writing a commit record to the WAL buffer
|
|
and flushing the buffer out to disk, in microseconds. A
|
|
nonzero delay can allow multiple transactions to be committed
|
|
with only one <function>fsync()</function> system call, if
|
|
system load is high enough that additional transactions become
|
|
ready to commit within the given interval. But the delay is
|
|
just wasted if no other transactions become ready to
|
|
commit. Therefore, the delay is only performed if at least
|
|
<varname>commit_siblings</varname> other transactions are
|
|
active at the instant that a server process has written its
|
|
commit record. The default is zero (no delay).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-commit-siblings" xreflabel="commit_siblings">
|
|
<term><varname>commit_siblings</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>commit_siblings</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Minimum number of concurrent open transactions to require
|
|
before performing the <varname>commit_delay</> delay. A larger
|
|
value makes it more probable that at least one other
|
|
transaction will become ready to commit during the delay
|
|
interval. The default is five transactions.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
<sect2 id="runtime-config-wal-checkpoints">
|
|
<title>Checkpoints</title>
|
|
|
|
<variablelist>
|
|
<varlistentry id="guc-checkpoint-segments" xreflabel="checkpoint_segments">
|
|
<term><varname>checkpoint_segments</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>checkpoint_segments</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Maximum number of log file segments between automatic WAL
|
|
checkpoints (each segment is normally 16 megabytes). The default
|
|
is three segments. Increasing this parameter can increase the
|
|
amount of time needed for crash recovery.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-checkpoint-timeout" xreflabel="checkpoint_timeout">
|
|
<term><varname>checkpoint_timeout</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>checkpoint_timeout</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Maximum time between automatic WAL checkpoints, in
|
|
seconds. The default is five minutes (<literal>5min</>).
|
|
Increasing this parameter can increase the amount of time needed
|
|
for crash recovery.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-checkpoint-completion-target" xreflabel="checkpoint_completion_target">
|
|
<term><varname>checkpoint_completion_target</varname> (<type>floating point</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>checkpoint_completion_target</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the target length of checkpoints, as a fraction of
|
|
the checkpoint interval. The default is 0.5.
|
|
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-checkpoint-warning" xreflabel="checkpoint_warning">
|
|
<term><varname>checkpoint_warning</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>checkpoint_warning</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Write a message to the server log if checkpoints caused by
|
|
the filling of checkpoint segment files happen closer together
|
|
than this many seconds (which suggests that
|
|
<varname>checkpoint_segments</> ought to be raised). The default is
|
|
30 seconds (<literal>30s</>). Zero disables the warning.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
<sect2 id="runtime-config-wal-archiving">
|
|
<title>Archiving</title>
|
|
|
|
<variablelist>
|
|
<varlistentry id="guc-archive-mode" xreflabel="archive_mode">
|
|
<term><varname>archive_mode</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>archive_mode</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When <varname>archive_mode</> is enabled, completed WAL segments
|
|
can be sent to archive storage by setting
|
|
<xref linkend="guc-archive-command">.
|
|
<varname>archive_mode</> and <varname>archive_command</> are
|
|
separate variables so that <varname>archive_command</> can be
|
|
changed without leaving archiving mode.
|
|
This parameter can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-archive-command" xreflabel="archive_command">
|
|
<term><varname>archive_command</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>archive_command</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The shell command to execute to archive a completed segment of
|
|
the WAL file series. Any <literal>%p</> in the string is
|
|
replaced by the path name of the file to archive, and any
|
|
<literal>%f</> is replaced by the file name only.
|
|
(The path name is relative to the working directory of the server,
|
|
i.e., the cluster's data directory.)
|
|
Use <literal>%%</> to embed an actual <literal>%</> character in the
|
|
command. For more information see <xref
|
|
linkend="backup-archiving-wal">.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line. It is ignored unless
|
|
<varname>archive_mode</> was enabled at server start.
|
|
If <varname>archive_command</> is an empty string (the default) while
|
|
<varname>archive_mode</> is enabled, then WAL archiving is temporarily
|
|
disabled, but the server continues to accumulate WAL segment files in
|
|
the expectation that a command will soon be provided.
|
|
</para>
|
|
<para>
|
|
It is important for the command to return a zero exit status if
|
|
and only if it succeeds. Examples:
|
|
<programlisting>
|
|
archive_command = 'cp "%p" /mnt/server/archivedir/"%f"'
|
|
archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Windows
|
|
</programlisting>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-archive-timeout" xreflabel="archive_timeout">
|
|
<term><varname>archive_timeout</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>archive_timeout</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The <xref linkend="guc-archive-command"> is only invoked on
|
|
completed WAL segments. Hence, if your server generates little WAL
|
|
traffic (or has slack periods where it does so), there could be a
|
|
long delay between the completion of a transaction and its safe
|
|
recording in archive storage. To put a limit on how old unarchived
|
|
data can be, you can set <varname>archive_timeout</> to force the
|
|
server to switch to a new WAL segment file periodically. When this
|
|
parameter is greater than zero, the server will switch to a new
|
|
segment file whenever this many seconds have elapsed since the last
|
|
segment file switch. Note that archived files that are closed early
|
|
due to a forced switch are still the same length as completely full
|
|
files. Therefore, it is unwise to use a very short
|
|
<varname>archive_timeout</> — it will bloat your archive
|
|
storage. <varname>archive_timeout</> settings of a minute or so are
|
|
usually reasonable. This parameter can only be set in the
|
|
<filename>postgresql.conf</> file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-query">
|
|
<title>Query Planning</title>
|
|
|
|
<sect2 id="runtime-config-query-enable">
|
|
<title>Planner Method Configuration</title>
|
|
|
|
<para>
|
|
These configuration parameters provide a crude method of
|
|
influencing the query plans chosen by the query optimizer. If
|
|
the default plan chosen by the optimizer for a particular query
|
|
is not optimal, a temporary solution can be found by using one
|
|
of these configuration parameters to force the optimizer to
|
|
choose a different plan. Turning one of these settings off
|
|
permanently is seldom a good idea, however.
|
|
Better ways to improve the quality of the
|
|
plans chosen by the optimizer include adjusting the <xref
|
|
linkend="runtime-config-query-constants"
|
|
endterm="runtime-config-query-constants-title">, running <xref
|
|
linkend="sql-analyze" endterm="sql-analyze-title"> more
|
|
frequently, increasing the value of the <xref
|
|
linkend="guc-default-statistics-target"> configuration parameter,
|
|
and increasing the amount of statistics collected for
|
|
specific columns using <command>ALTER TABLE SET
|
|
STATISTICS</command>.
|
|
</para>
|
|
|
|
<variablelist>
|
|
<varlistentry id="guc-enable-bitmapscan" xreflabel="enable_bitmapscan">
|
|
<term><varname>enable_bitmapscan</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary>bitmap scan</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>enable_bitmapscan</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the query planner's use of bitmap-scan plan
|
|
types. The default is <literal>on</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-enable-hashagg" xreflabel="enable_hashagg">
|
|
<term><varname>enable_hashagg</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>enable_hashagg</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the query planner's use of hashed
|
|
aggregation plan types. The default is <literal>on</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-enable-hashjoin" xreflabel="enable_hashjoin">
|
|
<term><varname>enable_hashjoin</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>enable_hashjoin</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the query planner's use of hash-join plan
|
|
types. The default is <literal>on</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-enable-indexscan" xreflabel="enable_indexscan">
|
|
<term><varname>enable_indexscan</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary>index scan</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>enable_indexscan</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the query planner's use of index-scan plan
|
|
types. The default is <literal>on</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-enable-mergejoin" xreflabel="enable_mergejoin">
|
|
<term><varname>enable_mergejoin</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>enable_mergejoin</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the query planner's use of merge-join plan
|
|
types. The default is <literal>on</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-enable-nestloop" xreflabel="enable_nestloop">
|
|
<term><varname>enable_nestloop</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>enable_nestloop</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the query planner's use of nested-loop join
|
|
plans. It's not possible to suppress nested-loop joins entirely,
|
|
but turning this variable off discourages the planner from using
|
|
one if there are other methods available. The default is
|
|
<literal>on</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-enable-seqscan" xreflabel="enable_seqscan">
|
|
<term><varname>enable_seqscan</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary>sequential scan</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>enable_seqscan</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the query planner's use of sequential scan
|
|
plan types. It's not possible to suppress sequential scans
|
|
entirely, but turning this variable off discourages the planner
|
|
from using one if there are other methods available. The
|
|
default is <literal>on</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-enable-sort" xreflabel="enable_sort">
|
|
<term><varname>enable_sort</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>enable_sort</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the query planner's use of explicit sort
|
|
steps. It's not possible to suppress explicit sorts entirely,
|
|
but turning this variable off discourages the planner from
|
|
using one if there are other methods available. The default
|
|
is <literal>on</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-enable-tidscan" xreflabel="enable_tidscan">
|
|
<term><varname>enable_tidscan</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>enable_tidscan</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the query planner's use of <acronym>TID</>
|
|
scan plan types. The default is <literal>on</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
<sect2 id="runtime-config-query-constants">
|
|
<title id="runtime-config-query-constants-title">
|
|
Planner Cost Constants
|
|
</title>
|
|
|
|
<para>
|
|
The <firstterm>cost</> variables described in this section are measured
|
|
on an arbitrary scale. Only their relative values matter, hence
|
|
scaling them all up or down by the same factor will result in no change
|
|
in the planner's choices. Traditionally, these variables have been
|
|
referenced to sequential page fetches as the unit of cost; that is,
|
|
<varname>seq_page_cost</> is conventionally set to <literal>1.0</>
|
|
and the other cost variables are set with reference to that. But
|
|
you can use a different scale if you prefer, such as actual execution
|
|
times in milliseconds on a particular machine.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
Unfortunately, there is no well-defined method for determining ideal
|
|
values for the cost variables. They are best treated as averages over
|
|
the entire mix of queries that a particular installation will get. This
|
|
means that changing them on the basis of just a few experiments is very
|
|
risky.
|
|
</para>
|
|
</note>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-seq-page-cost" xreflabel="seq_page_cost">
|
|
<term><varname>seq_page_cost</varname> (<type>floating point</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>seq_page_cost</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the planner's estimate of the cost of a disk page fetch
|
|
that is part of a series of sequential fetches. The default is 1.0.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-random-page-cost" xreflabel="random_page_cost">
|
|
<term><varname>random_page_cost</varname> (<type>floating point</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>random_page_cost</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the planner's estimate of the cost of a
|
|
non-sequentially-fetched disk page. The default is 4.0.
|
|
Reducing this value relative to <varname>seq_page_cost</>
|
|
will cause the system to prefer index scans; raising it will
|
|
make index scans look relatively more expensive. You can raise
|
|
or lower both values together to change the importance of disk I/O
|
|
costs relative to CPU costs, which are described by the following
|
|
parameters.
|
|
</para>
|
|
|
|
<tip>
|
|
<para>
|
|
Although the system will let you set <varname>random_page_cost</> to
|
|
less than <varname>seq_page_cost</>, it is not physically sensible
|
|
to do so. However, setting them equal makes sense if the database
|
|
is entirely cached in RAM, since in that case there is no penalty
|
|
for touching pages out of sequence. Also, in a heavily-cached
|
|
database you should lower both values relative to the CPU parameters,
|
|
since the cost of fetching a page already in RAM is much smaller
|
|
than it would normally be.
|
|
</para>
|
|
</tip>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-cpu-tuple-cost" xreflabel="cpu_tuple_cost">
|
|
<term><varname>cpu_tuple_cost</varname> (<type>floating point</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>cpu_tuple_cost</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the planner's estimate of the cost of processing
|
|
each row during a query.
|
|
The default is 0.01.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-cpu-index-tuple-cost" xreflabel="cpu_index_tuple_cost">
|
|
<term><varname>cpu_index_tuple_cost</varname> (<type>floating point</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>cpu_index_tuple_cost</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the planner's estimate of the cost of processing
|
|
each index entry during an index scan.
|
|
The default is 0.005.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-cpu-operator-cost" xreflabel="cpu_operator_cost">
|
|
<term><varname>cpu_operator_cost</varname> (<type>floating point</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>cpu_operator_cost</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the planner's estimate of the cost of processing each
|
|
operator or function executed during a query.
|
|
The default is 0.0025.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-effective-cache-size" xreflabel="effective_cache_size">
|
|
<term><varname>effective_cache_size</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>effective_cache_size</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the planner's assumption about the effective size of the
|
|
disk cache that is available to a single query. This is
|
|
factored into estimates of the cost of using an index; a
|
|
higher value makes it more likely index scans will be used, a
|
|
lower value makes it more likely sequential scans will be
|
|
used. When setting this parameter you should consider both
|
|
<productname>PostgreSQL</productname>'s shared buffers and the
|
|
portion of the kernel's disk cache that will be used for
|
|
<productname>PostgreSQL</productname> data files. Also, take
|
|
into account the expected number of concurrent queries on different
|
|
tables, since they will have to share the available
|
|
space. This parameter has no effect on the size of shared
|
|
memory allocated by <productname>PostgreSQL</productname>, nor
|
|
does it reserve kernel disk cache; it is used only for estimation
|
|
purposes. The default is 128 megabytes (<literal>128MB</>).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
|
|
</sect2>
|
|
<sect2 id="runtime-config-query-geqo">
|
|
<title>Genetic Query Optimizer</title>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-geqo" xreflabel="geqo">
|
|
<indexterm>
|
|
<primary>genetic query optimization</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>GEQO</primary>
|
|
<see>genetic query optimization</see>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>geqo</> configuration parameter</primary>
|
|
</indexterm>
|
|
<term><varname>geqo</varname> (<type>boolean</type>)</term>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables genetic query optimization, which is an
|
|
algorithm that attempts to do query planning without
|
|
exhaustive searching. This is on by default. The
|
|
<varname>geqo_threshold</varname> variable provides a more
|
|
granular way to disable GEQO for certain classes of queries.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-geqo-threshold" xreflabel="geqo_threshold">
|
|
<term><varname>geqo_threshold</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>geqo_threshold</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Use genetic query optimization to plan queries with at least
|
|
this many <literal>FROM</> items involved. (Note that a
|
|
<literal>FULL OUTER JOIN</> construct counts as only one <literal>FROM</>
|
|
item.) The default is 12. For simpler queries it is usually best
|
|
to use the deterministic, exhaustive planner, but for queries with
|
|
many tables the deterministic planner takes too long.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-geqo-effort" xreflabel="geqo_effort">
|
|
<term><varname>geqo_effort</varname>
|
|
(<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>geqo_effort</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls the trade off between planning time and query plan
|
|
efficiency in GEQO. This variable must be an integer in the
|
|
range from 1 to 10. The default value is five. Larger values
|
|
increase the time spent doing query planning, but also
|
|
increase the likelihood that an efficient query plan will be
|
|
chosen.
|
|
</para>
|
|
|
|
<para>
|
|
<varname>geqo_effort</varname> doesn't actually do anything
|
|
directly; it is only used to compute the default values for
|
|
the other variables that influence GEQO behavior (described
|
|
below). If you prefer, you can set the other parameters by
|
|
hand instead.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-geqo-pool-size" xreflabel="geqo_pool_size">
|
|
<term><varname>geqo_pool_size</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>geqo_pool_size</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls the pool size used by GEQO. The pool size is the
|
|
number of individuals in the genetic population. It must be
|
|
at least two, and useful values are typically 100 to 1000. If
|
|
it is set to zero (the default setting) then a suitable
|
|
default is chosen based on <varname>geqo_effort</varname> and
|
|
the number of tables in the query.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-geqo-generations" xreflabel="geqo_generations">
|
|
<term><varname>geqo_generations</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>geqo_generations</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls the number of generations used by GEQO. Generations
|
|
specifies the number of iterations of the algorithm. It must
|
|
be at least one, and useful values are in the same range as
|
|
the pool size. If it is set to zero (the default setting)
|
|
then a suitable default is chosen based on
|
|
<varname>geqo_pool_size</varname>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-geqo-selection-bias" xreflabel="geqo_selection_bias">
|
|
<term><varname>geqo_selection_bias</varname> (<type>floating point</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>geqo_selection_bias</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls the selection bias used by GEQO. The selection bias
|
|
is the selective pressure within the population. Values can be
|
|
from 1.50 to 2.00; the latter is the default.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
<sect2 id="runtime-config-query-other">
|
|
<title>Other Planner Options</title>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-default-statistics-target" xreflabel="default_statistics_target">
|
|
<term><varname>default_statistics_target</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>default_statistics_target</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the default statistics target for table columns that have
|
|
not had a column-specific target set via <command>ALTER TABLE
|
|
SET STATISTICS</>. Larger values increase the time needed to
|
|
do <command>ANALYZE</>, but might improve the quality of the
|
|
planner's estimates. The default is 10. For more information
|
|
on the use of statistics by the <productname>PostgreSQL</>
|
|
query planner, refer to <xref linkend="planner-stats">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-constraint-exclusion" xreflabel="constraint_exclusion">
|
|
<term><varname>constraint_exclusion</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary>constraint exclusion</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>constraint_exclusion</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables or disables the query planner's use of table constraints to
|
|
optimize queries. The default is <literal>off</>.
|
|
</para>
|
|
|
|
<para>
|
|
When this parameter is <literal>on</>, the planner compares
|
|
query conditions with table <literal>CHECK</> constraints, and
|
|
omits scanning tables for which the conditions contradict the
|
|
constraints. For example:
|
|
|
|
<programlisting>
|
|
CREATE TABLE parent(key integer, ...);
|
|
CREATE TABLE child1000(check (key between 1000 and 1999)) INHERITS(parent);
|
|
CREATE TABLE child2000(check (key between 2000 and 2999)) INHERITS(parent);
|
|
...
|
|
SELECT * FROM parent WHERE key = 2400;
|
|
</programlisting>
|
|
|
|
With constraint exclusion enabled, this <command>SELECT</>
|
|
will not scan <structname>child1000</> at all. This can
|
|
improve performance when inheritance is used to build
|
|
partitioned tables.
|
|
</para>
|
|
|
|
<para>
|
|
Currently, <varname>constraint_exclusion</> is disabled by
|
|
default because the constraint checks are relatively
|
|
expensive, and in many circumstances will yield no savings.
|
|
It is recommended to turn this on only if you are actually
|
|
using partitioned tables designed to take advantage of the
|
|
feature.
|
|
</para>
|
|
|
|
<para>
|
|
Refer to <xref linkend="ddl-partitioning"> for more information
|
|
on using constraint exclusion and partitioning.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-cursor-tuple-fraction" xreflabel="cursor_tuple_fraction">
|
|
<term><varname>cursor_tuple_fraction</varname> (<type>floating point</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>cursor_tuple_fraction</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the planner's estimate of the fraction of a cursor's rows that
|
|
will be retrieved. The default is 0.1. Smaller values of this
|
|
setting bias the planner towards using <quote>fast start</> plans
|
|
for cursors, which will retrieve the first few rows quickly while
|
|
perhaps taking a long time to fetch all rows. Larger values
|
|
put more emphasis on the total estimated time. At the maximum
|
|
setting of 1.0, cursors are planned exactly like regular queries,
|
|
considering only the total estimated time and not how soon the
|
|
first rows might be delivered.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-from-collapse-limit" xreflabel="from_collapse_limit">
|
|
<term><varname>from_collapse_limit</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>from_collapse_limit</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The planner will merge sub-queries into upper queries if the
|
|
resulting <literal>FROM</literal> list would have no more than
|
|
this many items. Smaller values reduce planning time but might
|
|
yield inferior query plans. The default is eight. It is usually
|
|
wise to keep this less than <xref linkend="guc-geqo-threshold">.
|
|
For more information see <xref linkend="explicit-joins">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-join-collapse-limit" xreflabel="join_collapse_limit">
|
|
<term><varname>join_collapse_limit</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>join_collapse_limit</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The planner will rewrite explicit <literal>JOIN</>
|
|
constructs (except <literal>FULL JOIN</>s) into lists of
|
|
<literal>FROM</> items whenever a list of no more than this many items
|
|
would result. Smaller values reduce planning time but might
|
|
yield inferior query plans.
|
|
</para>
|
|
|
|
<para>
|
|
By default, this variable is set the same as
|
|
<varname>from_collapse_limit</varname>, which is appropriate
|
|
for most uses. Setting it to 1 prevents any reordering of
|
|
explicit <literal>JOIN</>s. Thus, the explicit join order
|
|
specified in the query will be the actual order in which the
|
|
relations are joined. The query planner does not always choose
|
|
the optimal join order; advanced users can elect to
|
|
temporarily set this variable to 1, and then specify the join
|
|
order they desire explicitly.
|
|
For more information see <xref linkend="explicit-joins">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-logging">
|
|
<title>Error Reporting and Logging</title>
|
|
|
|
<indexterm zone="runtime-config-logging">
|
|
<primary>server log</primary>
|
|
</indexterm>
|
|
|
|
<sect2 id="runtime-config-logging-where">
|
|
<title>Where To Log</title>
|
|
|
|
<indexterm zone="runtime-config-logging-where">
|
|
<primary>where to log</primary>
|
|
</indexterm>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-log-destination" xreflabel="log_destination">
|
|
<term><varname>log_destination</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_destination</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
<productname>PostgreSQL</productname> supports several methods
|
|
for logging server messages, including
|
|
<systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem> and
|
|
<systemitem>syslog</systemitem>. On Windows,
|
|
<systemitem>eventlog</systemitem> is also supported. Set this
|
|
parameter to a list of desired log destinations separated by
|
|
commas. The default is to log to <systemitem>stderr</systemitem>
|
|
only.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
<para>
|
|
If <systemitem>csvlog</> is included in <varname>log_destination</>,
|
|
log entries are output in <quote>comma separated
|
|
value</> format, which is convenient for loading them into programs.
|
|
See <xref linkend="runtime-config-logging-csvlog"> for details.
|
|
<varname>logging_collector</varname> must be enabled to generate
|
|
CSV-format log output.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
On most Unix systems, you will need to alter the configuration of
|
|
your system's <application>syslog</application> daemon in order
|
|
to make use of the <systemitem>syslog</systemitem> option for
|
|
<varname>log_destination</>. <productname>PostgreSQL</productname>
|
|
can log to <application>syslog</application> facilities
|
|
<literal>LOCAL0</> through <literal>LOCAL7</> (see <xref
|
|
linkend="guc-syslog-facility">), but the default
|
|
<application>syslog</application> configuration on most platforms
|
|
will discard all such messages. You will need to add something like
|
|
<programlisting>
|
|
local0.* /var/log/postgresql
|
|
</programlisting>
|
|
to the <application>syslog</application> daemon's configuration file
|
|
to make it work.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-logging-collector" xreflabel="logging_collector">
|
|
<term><varname>logging_collector</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>logging_collector</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This parameter allows messages sent to <application>stderr</>,
|
|
and CSV-format log output, to be
|
|
captured and redirected into log files.
|
|
This approach is often more useful than
|
|
logging to <application>syslog</>, since some types of messages
|
|
might not appear in <application>syslog</> output (a common example
|
|
is dynamic-linker failure messages).
|
|
This parameter can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-directory" xreflabel="log_directory">
|
|
<term><varname>log_directory</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_directory</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When <varname>logging_collector</> is enabled,
|
|
this parameter determines the directory in which log files will be created.
|
|
It can be specified as an absolute path, or relative to the
|
|
cluster data directory.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-filename" xreflabel="log_filename">
|
|
<term><varname>log_filename</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_filename</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When <varname>logging_collector</varname> is enabled,
|
|
this parameter sets the file names of the created log files. The value
|
|
is treated as a <systemitem>strftime</systemitem> pattern,
|
|
so <literal>%</literal>-escapes can be used to specify time-varying
|
|
file names. (Note that if there are
|
|
any time-zone-dependent <literal>%</literal>-escapes, the computation
|
|
is done in the zone specified by <xref linkend="guc-log-timezone">.)
|
|
If no <literal>%</literal>-escapes are present,
|
|
<productname>PostgreSQL</productname> will append the epoch of the new
|
|
log file's creation time. For example, if
|
|
<varname>log_filename</varname> were <literal>server_log</literal>,
|
|
then the chosen file name would be <literal>server_log.1093827753</>
|
|
for a log starting at Sun Aug 29 19:02:33 2004 MST.
|
|
Note that the system's <systemitem>strftime</systemitem> is not used
|
|
directly, so platform-specific (nonstandard) extensions do not work.
|
|
</para>
|
|
<para>
|
|
If CSV-format output is enabled in <varname>log_destination</>,
|
|
<literal>.csv</> will be appended to the timestamped
|
|
log file name to create the file name for CSV-format output.
|
|
(If <varname>log_filename</> ends in <literal>.log</>, the suffix is
|
|
replaced instead.)
|
|
In the case of the example above, the CSV
|
|
file name will be <literal>server_log.1093827753.csv</literal>.
|
|
</para>
|
|
<para>
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-rotation-age" xreflabel="log_rotation_age">
|
|
<term><varname>log_rotation_age</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_rotation_age</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When <varname>logging_collector</varname> is enabled,
|
|
this parameter determines the maximum lifetime of an individual log file.
|
|
After this many minutes have elapsed, a new log file will
|
|
be created. Set to zero to disable time-based creation of
|
|
new log files.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-rotation-size" xreflabel="log_rotation_size">
|
|
<term><varname>log_rotation_size</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_rotation_size</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When <varname>logging_collector</varname> is enabled,
|
|
this parameter determines the maximum size of an individual log file.
|
|
After this many kilobytes have been emitted into a log file,
|
|
a new log file will be created. Set to zero to disable size-based
|
|
creation of new log files.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-truncate-on-rotation" xreflabel="log_truncate_on_rotation">
|
|
<term><varname>log_truncate_on_rotation</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_truncate_on_rotation</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When <varname>logging_collector</varname> is enabled,
|
|
this parameter will cause <productname>PostgreSQL</productname> to truncate (overwrite),
|
|
rather than append to, any existing log file of the same name.
|
|
However, truncation will occur only when a new file is being opened
|
|
due to time-based rotation, not during server startup or size-based
|
|
rotation. When off, pre-existing files will be appended to in
|
|
all cases. For example, using this setting in combination with
|
|
a <varname>log_filename</varname> like <literal>postgresql-%H.log</literal>
|
|
would result in generating twenty-four hourly log files and then
|
|
cyclically overwriting them.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
<para>
|
|
Example: To keep 7 days of logs, one log file per day named
|
|
<literal>server_log.Mon</literal>, <literal>server_log.Tue</literal>,
|
|
etc, and automatically overwrite last week's log with this week's log,
|
|
set <varname>log_filename</varname> to <literal>server_log.%a</literal>,
|
|
<varname>log_truncate_on_rotation</varname> to <literal>on</literal>, and
|
|
<varname>log_rotation_age</varname> to <literal>1440</literal>.
|
|
</para>
|
|
<para>
|
|
Example: To keep 24 hours of logs, one log file per hour, but
|
|
also rotate sooner if the log file size exceeds 1GB, set
|
|
<varname>log_filename</varname> to <literal>server_log.%H%M</literal>,
|
|
<varname>log_truncate_on_rotation</varname> to <literal>on</literal>,
|
|
<varname>log_rotation_age</varname> to <literal>60</literal>, and
|
|
<varname>log_rotation_size</varname> to <literal>1000000</literal>.
|
|
Including <literal>%M</> in <varname>log_filename</varname> allows
|
|
any size-driven rotations that might occur to select a file name
|
|
different from the hour's initial file name.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-syslog-facility" xreflabel="syslog_facility">
|
|
<term><varname>syslog_facility</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>syslog_facility</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When logging to <application>syslog</> is enabled, this parameter
|
|
determines the <application>syslog</application>
|
|
<quote>facility</quote> to be used. You can choose
|
|
from <literal>LOCAL0</>, <literal>LOCAL1</>,
|
|
<literal>LOCAL2</>, <literal>LOCAL3</>, <literal>LOCAL4</>,
|
|
<literal>LOCAL5</>, <literal>LOCAL6</>, <literal>LOCAL7</>;
|
|
the default is <literal>LOCAL0</>. See also the
|
|
documentation of your system's
|
|
<application>syslog</application> daemon.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-syslog-ident" xreflabel="syslog_ident">
|
|
<term><varname>syslog_ident</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>syslog_identity</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When logging to <application>syslog</> is enabled, this parameter
|
|
determines the program name used to identify
|
|
<productname>PostgreSQL</productname> messages in
|
|
<application>syslog</application> logs. The default is
|
|
<literal>postgres</literal>.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
<sect2 id="runtime-config-logging-when">
|
|
<title>When To Log</title>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-client-min-messages" xreflabel="client_min_messages">
|
|
<term><varname>client_min_messages</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>client_min_messages</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls which message levels are sent to the client.
|
|
Valid values are <literal>DEBUG5</>,
|
|
<literal>DEBUG4</>, <literal>DEBUG3</>, <literal>DEBUG2</>,
|
|
<literal>DEBUG1</>, <literal>LOG</>, <literal>NOTICE</>,
|
|
<literal>WARNING</>, <literal>ERROR</>, <literal>FATAL</>,
|
|
and <literal>PANIC</>. Each level
|
|
includes all the levels that follow it. The later the level,
|
|
the fewer messages are sent. The default is
|
|
<literal>NOTICE</>. Note that <literal>LOG</> has a different
|
|
rank here than in <varname>log_min_messages</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-min-messages" xreflabel="log_min_messages">
|
|
<term><varname>log_min_messages</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_min_messages</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls which message levels are written to the server log.
|
|
Valid values are <literal>DEBUG5</>, <literal>DEBUG4</>,
|
|
<literal>DEBUG3</>, <literal>DEBUG2</>, <literal>DEBUG1</>,
|
|
<literal>INFO</>, <literal>NOTICE</>, <literal>WARNING</>,
|
|
<literal>ERROR</>, <literal>LOG</>, <literal>FATAL</>, and
|
|
<literal>PANIC</>. Each level includes all the levels that
|
|
follow it. The later the level, the fewer messages are sent
|
|
to the log. The default is <literal>WARNING</>. Note that
|
|
<literal>LOG</> has a different rank here than in
|
|
<varname>client_min_messages</>.
|
|
Only superusers can change this setting.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-error-verbosity" xreflabel="log_error_verbosity">
|
|
<term><varname>log_error_verbosity</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_error_verbosity</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls the amount of detail written in the server log for each
|
|
message that is logged. Valid values are <literal>TERSE</>,
|
|
<literal>DEFAULT</>, and <literal>VERBOSE</>, each adding more
|
|
fields to displayed messages.
|
|
Only superusers can change this setting.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-min-error-statement" xreflabel="log_min_error_statement">
|
|
<term><varname>log_min_error_statement</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_min_error_statement</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls whether or not the SQL statement that causes an error
|
|
condition will be recorded in the server log. The current
|
|
SQL statement is included in the log entry for any message of
|
|
the specified severity or higher.
|
|
Valid values are <literal>DEBUG5</literal>,
|
|
<literal>DEBUG4</literal>, <literal>DEBUG3</literal>,
|
|
<literal>DEBUG2</literal>, <literal>DEBUG1</literal>,
|
|
<literal>INFO</literal>, <literal>NOTICE</literal>,
|
|
<literal>WARNING</literal>, <literal>ERROR</literal>,
|
|
<literal>LOG</literal>,
|
|
<literal>FATAL</literal>, and <literal>PANIC</literal>.
|
|
The default is <literal>ERROR</literal>, which means statements
|
|
causing errors, log messages, fatal errors, or panics will be logged.
|
|
To effectively turn off logging of failing statements,
|
|
set this parameter to <literal>PANIC</literal>.
|
|
Only superusers can change this setting.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-min-duration-statement" xreflabel="log_min_duration_statement">
|
|
<term><varname>log_min_duration_statement</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_min_duration_statement</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Causes the duration of each completed statement to be logged
|
|
if the statement ran for at least the specified number of
|
|
milliseconds. Setting this to zero prints all statement durations.
|
|
Minus-one (the default) disables logging statement durations.
|
|
For example, if you set it to <literal>250ms</literal>
|
|
then all SQL statements that run 250ms or longer will be
|
|
logged. Enabling this parameter can be helpful in tracking down
|
|
unoptimized queries in your applications.
|
|
Only superusers can change this setting.
|
|
</para>
|
|
|
|
<para>
|
|
For clients using extended query protocol, durations of the Parse,
|
|
Bind, and Execute steps are logged independently.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
When using this option together with
|
|
<xref linkend="guc-log-statement">,
|
|
the text of statements that are logged because of
|
|
<varname>log_statement</> will not be repeated in the
|
|
duration log message.
|
|
If you are not using <application>syslog</>, it is recommended
|
|
that you log the PID or session ID using
|
|
<xref linkend="guc-log-line-prefix">
|
|
so that you can link the statement message to the later
|
|
duration message using the process ID or session ID.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-silent-mode" xreflabel="silent_mode">
|
|
<term><varname>silent_mode</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>silent_mode</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Runs the server silently. If this parameter is set, the server
|
|
will automatically run in background and any controlling
|
|
terminals are disassociated.
|
|
The server's standard output and standard error are redirected
|
|
to <literal>/dev/null</>, so any messages sent to them will be lost.
|
|
Unless <application>syslog</> logging is selected or
|
|
<varname>logging_collector</> is enabled, using this parameter
|
|
is discouraged because it makes it impossible to see error messages.
|
|
This parameter can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
|
|
<para>
|
|
<xref linkend="runtime-config-severity-levels"> explains the message
|
|
severity levels used by <productname>PostgreSQL</>. If logging output
|
|
is sent to <systemitem>syslog</systemitem> or Windows'
|
|
<systemitem>eventlog</systemitem>, the severity levels are translated
|
|
as shown in the table.
|
|
</para>
|
|
|
|
<table id="runtime-config-severity-levels">
|
|
<title>Message severity levels</title>
|
|
<tgroup cols="4">
|
|
<thead>
|
|
<row>
|
|
<entry>Severity</entry>
|
|
<entry>Usage</entry>
|
|
<entry><systemitem>syslog</></entry>
|
|
<entry><systemitem>eventlog</></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>DEBUG1..DEBUG5</></entry>
|
|
<entry>Provides successively-more-detailed information for use by
|
|
developers.</entry>
|
|
<entry><literal>DEBUG</></entry>
|
|
<entry><literal>INFORMATION</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>INFO</></entry>
|
|
<entry>Provides information implicitly requested by the user,
|
|
e.g., output from <command>VACUUM VERBOSE</>.</entry>
|
|
<entry><literal>INFO</></entry>
|
|
<entry><literal>INFORMATION</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>NOTICE</></entry>
|
|
<entry>Provides information that might be helpful to users, e.g.,
|
|
notice of truncation of long identifiers.</entry>
|
|
<entry><literal>NOTICE</></entry>
|
|
<entry><literal>INFORMATION</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>WARNING</></entry>
|
|
<entry>Provides warnings of likely problems, e.g., <command>COMMIT</>
|
|
outside a transaction block.</entry>
|
|
<entry><literal>NOTICE</></entry>
|
|
<entry><literal>WARNING</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>ERROR</></entry>
|
|
<entry>Reports an error that caused the current command to
|
|
abort.</entry>
|
|
<entry><literal>WARNING</></entry>
|
|
<entry><literal>ERROR</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>LOG</></entry>
|
|
<entry>Reports information of interest to administrators, e.g.,
|
|
checkpoint activity.</entry>
|
|
<entry><literal>INFO</></entry>
|
|
<entry><literal>INFORMATION</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>FATAL</></entry>
|
|
<entry>Reports an error that caused the current session to
|
|
abort.</entry>
|
|
<entry><literal>ERR</></entry>
|
|
<entry><literal>ERROR</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>PANIC</></entry>
|
|
<entry>Reports an error that caused all database sessions to abort.</entry>
|
|
<entry><literal>CRIT</></entry>
|
|
<entry><literal>ERROR</></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
<sect2 id="runtime-config-logging-what">
|
|
<title>What To Log</title>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry>
|
|
<term><varname>debug_print_parse</varname> (<type>boolean</type>)</term>
|
|
<term><varname>debug_print_rewritten</varname> (<type>boolean</type>)</term>
|
|
<term><varname>debug_print_plan</varname> (<type>boolean</type>)</term>
|
|
<term><varname>debug_pretty_print</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>debug_print_parse</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>debug_print_rewritten</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>debug_print_plan</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>debug_pretty_print</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
These parameters enable various debugging output to be emitted.
|
|
For each executed query, they print
|
|
the resulting parse tree, the query rewriter output, or the
|
|
execution plan. <varname>debug_pretty_print</varname> indents
|
|
these displays to produce a more readable but much longer
|
|
output format. <varname>client_min_messages</varname> or
|
|
<varname>log_min_messages</varname> must be
|
|
<literal>DEBUG1</literal> or lower to actually send this output
|
|
to the client or the server log, respectively.
|
|
These parameters are off by default.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-checkpoints" xreflabel="log_checkpoints">
|
|
<term><varname>log_checkpoints</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_checkpoints</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Causes checkpoints to be logged in the server log. Some
|
|
statistics about each checkpoint are included in the log messages,
|
|
including the number of buffers written and the time spent writing
|
|
them.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line. The default is off.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-connections" xreflabel="log_connections">
|
|
<term><varname>log_connections</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_connections</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Causes each attempted connection to the server to be logged,
|
|
as well as successful completion of client authentication.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line. The default is off.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
Some client programs, like <application>psql</>, attempt
|
|
to connect twice while determining if a password is required, so
|
|
duplicate <quote>connection received</> messages do not
|
|
necessarily indicate a problem.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-disconnections" xreflabel="log_disconnections">
|
|
<term><varname>log_disconnections</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_disconnections</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This outputs a line in the server log similar to
|
|
<varname>log_connections</varname> but at session termination,
|
|
and includes the duration of the session. This is off by
|
|
default.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
|
|
<varlistentry id="guc-log-duration" xreflabel="log_duration">
|
|
<term><varname>log_duration</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_duration</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Causes the duration of every completed statement to be logged.
|
|
The default is <literal>off</>.
|
|
Only superusers can change this setting.
|
|
</para>
|
|
|
|
<para>
|
|
For clients using extended query protocol, durations of the Parse,
|
|
Bind, and Execute steps are logged independently.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
The difference between setting this option and setting
|
|
<xref linkend="guc-log-min-duration-statement"> to zero is that
|
|
exceeding <varname>log_min_duration_statement</> forces the text of
|
|
the query to be logged, but this option doesn't. Thus, if
|
|
<varname>log_duration</> is <literal>on</> and
|
|
<varname>log_min_duration_statement</> has a positive value, all
|
|
durations are logged but the query text is included only for
|
|
statements exceeding the threshold. This behavior can be useful for
|
|
gathering statistics in high-load installations.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-hostname" xreflabel="log_hostname">
|
|
<term><varname>log_hostname</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_hostname</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
By default, connection log messages only show the IP address of the
|
|
connecting host. Turning on this parameter causes logging of the
|
|
host name as well. Note that depending on your host name resolution
|
|
setup this might impose a non-negligible performance penalty.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-line-prefix" xreflabel="log_line_prefix">
|
|
<term><varname>log_line_prefix</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_line_prefix</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This is a <function>printf</>-style string that is output at the
|
|
beginning of each log line.
|
|
<literal>%</> characters begin <quote>escape sequences</>
|
|
that are replaced with status information as outlined below.
|
|
Unrecognized escapes are ignored. Other
|
|
characters are copied straight to the log line. Some escapes are
|
|
only recognized by session processes, and do not apply to
|
|
background processes such as the main server process.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line. The default is an empty string.
|
|
|
|
<informaltable>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Escape</entry>
|
|
<entry>Effect</entry>
|
|
<entry>Session only</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>%u</literal></entry>
|
|
<entry>User name</entry>
|
|
<entry>yes</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%d</literal></entry>
|
|
<entry>Database name</entry>
|
|
<entry>yes</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%r</literal></entry>
|
|
<entry>Remote host name or IP address, and remote port</entry>
|
|
<entry>yes</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%h</literal></entry>
|
|
<entry>Remote host name or IP address</entry>
|
|
<entry>yes</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%p</literal></entry>
|
|
<entry>Process ID</entry>
|
|
<entry>no</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%t</literal></entry>
|
|
<entry>Time stamp without milliseconds</entry>
|
|
<entry>no</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%m</literal></entry>
|
|
<entry>Time stamp with milliseconds</entry>
|
|
<entry>no</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%i</literal></entry>
|
|
<entry>Command tag: type of session's current command</entry>
|
|
<entry>yes</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%c</literal></entry>
|
|
<entry>Session ID: see below</entry>
|
|
<entry>no</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%l</literal></entry>
|
|
<entry>Number of the log line for each session or process, starting at 1</entry>
|
|
<entry>no</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%s</literal></entry>
|
|
<entry>Process start time stamp</entry>
|
|
<entry>no</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%v</literal></entry>
|
|
<entry>Virtual transaction ID (backendID/localXID)</entry>
|
|
<entry>no</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%x</literal></entry>
|
|
<entry>Transaction ID (0 if none is assigned)</entry>
|
|
<entry>no</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%q</literal></entry>
|
|
<entry>Produces no output, but tells non-session
|
|
processes to stop at this point in the string; ignored by
|
|
session processes</entry>
|
|
<entry>no</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>%%</literal></entry>
|
|
<entry>Literal <literal>%</></entry>
|
|
<entry>no</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</informaltable>
|
|
|
|
The <literal>%c</> escape prints a quasi-unique session identifier,
|
|
consisting of two 4-byte hexadecimal numbers (without leading zeros)
|
|
separated by a dot. The numbers are the process start time and the
|
|
process ID, so <literal>%c</> can also be used as a space saving way
|
|
of printing those items.
|
|
</para>
|
|
|
|
<tip>
|
|
<para>
|
|
If you set a nonempty value for <varname>log_line_prefix</>,
|
|
you should usually make its last character be a space, to provide
|
|
visual separation from the rest of the log line. A punctuation
|
|
character could be used too.
|
|
</para>
|
|
</tip>
|
|
|
|
<tip>
|
|
<para>
|
|
<application>Syslog</> produces its own
|
|
time stamp and process ID information, so you probably do not want to
|
|
use those escapes if you are logging to <application>syslog</>.
|
|
</para>
|
|
</tip>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-lock-waits" xreflabel="log_lock_waits">
|
|
<term><varname>log_lock_waits</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_lock_waits</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls whether a log message is produced when a session waits
|
|
longer than <xref linkend="guc-deadlock-timeout"> to acquire a
|
|
lock. This is useful in determining if lock waits are causing
|
|
poor performance. The default is <literal>off</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-statement" xreflabel="log_statement">
|
|
<term><varname>log_statement</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_statement</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls which SQL statements are logged. Valid values are
|
|
<literal>none</>, <literal>ddl</>, <literal>mod</>, and
|
|
<literal>all</>. <literal>ddl</> logs all data definition
|
|
statements, such as <command>CREATE</>, <command>ALTER</>, and
|
|
<command>DROP</> statements. <literal>mod</> logs all
|
|
<literal>ddl</> statements, plus data-modifying statements
|
|
such as <command>INSERT</>,
|
|
<command>UPDATE</>, <command>DELETE</>, <command>TRUNCATE</>,
|
|
and <command>COPY FROM</>.
|
|
<command>PREPARE</>, <command>EXECUTE</>, and
|
|
<command>EXPLAIN ANALYZE</> statements are also logged if their
|
|
contained command is of an appropriate type. For clients using
|
|
extended query protocol, logging occurs when an Execute message
|
|
is received, and values of the Bind parameters are included
|
|
(with any embedded single-quote marks doubled).
|
|
</para>
|
|
|
|
<para>
|
|
The default is <literal>none</>. Only superusers can change this
|
|
setting.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
Statements that contain simple syntax errors are not logged
|
|
even by the <varname>log_statement</> = <literal>all</> setting,
|
|
because the log message is emitted only after basic parsing has
|
|
been done to determine the statement type. In the case of extended
|
|
query protocol, this setting likewise does not log statements that
|
|
fail before the Execute phase (i.e., during parse analysis or
|
|
planning). Set <varname>log_min_error_statement</> to
|
|
<literal>ERROR</> (or lower) to log such statements.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-temp-files" xreflabel="log_temp_files">
|
|
<term><varname>log_temp_files</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_temp_files</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls whether temporary files are logged when deleted.
|
|
Temporary files can be
|
|
created for sorts, hashes, and temporary query results.
|
|
A value of zero logs all temporary files, and positive
|
|
values log only files whose size is equal or greater than
|
|
the specified number of kilobytes. The
|
|
default is <literal>-1</>, which disables this logging.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-timezone" xreflabel="log_timezone">
|
|
<term><varname>log_timezone</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_timezone</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the time zone used for timestamps written in the log.
|
|
Unlike <xref linkend="guc-timezone">, this value is cluster-wide,
|
|
so that all sessions will report timestamps consistently.
|
|
The default is <literal>unknown</>, which means to use whatever
|
|
the system environment specifies as the time zone. See <xref
|
|
linkend="datatype-timezones"> for more information.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
<sect2 id="runtime-config-logging-csvlog">
|
|
<title>Using CSV-Format Log Output</title>
|
|
|
|
<para>
|
|
Including <literal>csvlog</> in the <varname>log_destination</> list
|
|
provides a convenient way to import log files into a database table.
|
|
This option emits log lines in comma-separated-value format,
|
|
with these columns: timestamp with milliseconds, user name, database
|
|
name, process ID, host:port number, session ID, per-session or -process line
|
|
number, command tag, session start time, virtual transaction ID,
|
|
regular transaction id, error severity, SQL state code, error message,
|
|
error message detail, hint, internal query that led to the error (if
|
|
any), character count of the error position thereof, error context,
|
|
user query that led to the error (if any and enabled by
|
|
<varname>log_min_error_statement</>), character count of the error
|
|
position thereof, location of the error in the PostgreSQL source code
|
|
(if <varname>log_error_verbosity</> is set to <literal>verbose</>).
|
|
Here is a sample table definition for storing CSV-format log output:
|
|
|
|
<programlisting>
|
|
CREATE TABLE postgres_log
|
|
(
|
|
log_time timestamp(3) with time zone,
|
|
user_name text,
|
|
database_name text,
|
|
process_id integer,
|
|
connection_from text,
|
|
session_id text,
|
|
session_line_num bigint,
|
|
command_tag text,
|
|
session_start_time timestamp with time zone,
|
|
virtual_transaction_id text,
|
|
transaction_id bigint,
|
|
error_severity text,
|
|
sql_state_code text,
|
|
message text,
|
|
detail text,
|
|
hint text,
|
|
internal_query text,
|
|
internal_query_pos integer,
|
|
context text,
|
|
query text,
|
|
query_pos integer,
|
|
location text,
|
|
PRIMARY KEY (session_id, session_line_num)
|
|
);
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
To import a log file into this table, use the <command>COPY FROM</>
|
|
command:
|
|
|
|
<programlisting>
|
|
COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
There are a few things you need to do to simplify importing CSV log
|
|
files easily and automatically:
|
|
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>
|
|
Set <varname>log_filename</varname> and
|
|
<varname>log_rotation_age</> to provide a consistent,
|
|
predictable naming scheme for your log files. This lets you
|
|
predict what the file name will be and know when an individual log
|
|
file is complete and therefore ready to be imported.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
Set <varname>log_rotation_size</varname> to 0 to disable
|
|
size-based log rotation, as it makes the log file name difficult
|
|
to predict.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
Set <varname>log_truncate_on_rotation</varname> to <literal>on</> so
|
|
that old log data isn't mixed with the new in the same file.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
The table definition above includes a primary key specification.
|
|
This is useful to protect against accidentally importing the same
|
|
information twice. The <command>COPY</> command commits all of the
|
|
data it imports at one time, so any error will cause the entire
|
|
import to fail. If you import a partial log file and later import
|
|
the file again when it is complete, the primary key violation will
|
|
cause the import to fail. Wait until the log is complete and
|
|
closed before importing. This procedure will also protect against
|
|
accidentally importing a partial line that hasn't been completely
|
|
written, which would also cause <command>COPY</> to fail.
|
|
</para>
|
|
</listitem>
|
|
</orderedlist>
|
|
</para>
|
|
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-statistics">
|
|
<title>Run-Time Statistics</title>
|
|
|
|
<sect2 id="runtime-config-statistics-collector">
|
|
<title>Query and Index Statistics Collector</title>
|
|
|
|
<para>
|
|
These parameters control server-wide statistics collection features.
|
|
When statistics collection is enabled, the data that is produced can be
|
|
accessed via the <structname>pg_stat</structname> and
|
|
<structname>pg_statio</structname> family of system views.
|
|
Refer to <xref linkend="monitoring"> for more information.
|
|
</para>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-track-activities" xreflabel="track_activities">
|
|
<term><varname>track_activities</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>track_activities</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables the collection of information on the currently
|
|
executing command of each session, along with the time at
|
|
which that command began execution. This parameter is on by
|
|
default. Note that even when enabled, this information is not
|
|
visible to all users, only to superusers and the user owning
|
|
the session being reported on; so it should not represent a
|
|
security risk.
|
|
Only superusers can change this setting.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-track-activity-query-size" xreflabel="track_activity_query_size">
|
|
<term><varname>track_activity_query_size</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>track_activity_query_size</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the number of bytes reserved to track the currently
|
|
executing command for each active session, for the
|
|
<structname>pg_stat_activity</>.<structfield>current_query</> field.
|
|
The default value is 1024. This parameter can only be set at server
|
|
start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-track-counts" xreflabel="track_counts">
|
|
<term><varname>track_counts</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>track_counts</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables collection of statistics on database activity.
|
|
This parameter is on by default, because the autovacuum
|
|
daemon needs the collected information.
|
|
Only superusers can change this setting.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-track-functions" xreflabel="track_functions">
|
|
<term><varname>track_functions</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>track_functions</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables tracking of function call counts and time used. Specify
|
|
<literal>pl</literal> to count only procedural language functions,
|
|
<literal>all</literal> to also track SQL and C language functions.
|
|
The default is <literal>none</literal>.
|
|
Only superusers can change this setting.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-update-process-title" xreflabel="update_process_title">
|
|
<term><varname>update_process_title</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>update_process_title</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Enables updating of the process title every time a new SQL command
|
|
is received by the server. The process title is typically viewed
|
|
by the <command>ps</> command,
|
|
or in Windows by using the <application>Process Explorer</>.
|
|
Only superusers can change this setting.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
<sect2 id="runtime-config-statistics-monitor">
|
|
<title>Statistics Monitoring</title>
|
|
<variablelist>
|
|
|
|
<varlistentry>
|
|
<term><varname>log_statement_stats</varname> (<type>boolean</type>)</term>
|
|
<term><varname>log_parser_stats</varname> (<type>boolean</type>)</term>
|
|
<term><varname>log_planner_stats</varname> (<type>boolean</type>)</term>
|
|
<term><varname>log_executor_stats</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_statement_stats</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>log_parser_stats</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>log_planner_stats</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>log_executor_stats</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
For each query, write performance statistics of the respective
|
|
module to the server log. This is a crude profiling
|
|
instrument. <varname>log_statement_stats</varname> reports total
|
|
statement statistics, while the others report per-module statistics.
|
|
<varname>log_statement_stats</varname> cannot be enabled together with
|
|
any of the per-module options. All of these options are disabled by
|
|
default. Only superusers can change these settings.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-autovacuum">
|
|
<title>Automatic Vacuuming</title>
|
|
|
|
<indexterm>
|
|
<primary>autovacuum</primary>
|
|
<secondary>configuration parameters</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
These settings control the behavior of the <firstterm>autovacuum</>
|
|
feature. Refer to <xref linkend="autovacuum"> for
|
|
more information.
|
|
</para>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-autovacuum" xreflabel="autovacuum">
|
|
<term><varname>autovacuum</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>autovacuum</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls whether the server should run the
|
|
autovacuum launcher daemon. This is on by default; however,
|
|
<xref linkend="guc-track-counts"> must also be turned on for
|
|
autovacuum to work.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
<para>
|
|
Note that even when this parameter is disabled, the system
|
|
will launch autovacuum processes if necessary to
|
|
prevent transaction ID wraparound. See <xref
|
|
linkend="vacuum-for-wraparound"> for more information.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-log-autovacuum-min-duration" xreflabel="log_autovacuum_min_duration">
|
|
<term><varname>log_autovacuum_min_duration</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>log_autovacuum_min_duration</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Causes each action executed by autovacuum to be logged if it ran for at
|
|
least the specified number of milliseconds. Setting this to zero logs
|
|
all autovacuum actions. Minus-one (the default) disables logging
|
|
autovacuum actions. For example, if you set this to
|
|
<literal>250ms</literal> then all automatic vacuums and analyzes that run
|
|
250ms or longer will be logged. Enabling this parameter can be helpful
|
|
in tracking autovacuum activity. This setting can only be set in
|
|
the <filename>postgresql.conf</> file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-autovacuum-max-workers" xreflabel="autovacuum_max_workers">
|
|
<term><varname>autovacuum_max_workers</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>autovacuum_max_workers</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the maximum number of autovacuum processes (other than the
|
|
autovacuum launcher) which may be running at any one time. The default
|
|
is three. This parameter can only be set in
|
|
the <filename>postgresql.conf</> file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-autovacuum-naptime" xreflabel="autovacuum_naptime">
|
|
<term><varname>autovacuum_naptime</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>autovacuum_naptime</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the minimum delay between autovacuum runs on any given
|
|
database. In each round the daemon examines the
|
|
database and issues <command>VACUUM</> and <command>ANALYZE</> commands
|
|
as needed for tables in that database. The delay is measured
|
|
in seconds, and the default is one minute (<literal>1m</>).
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-autovacuum-vacuum-threshold" xreflabel="autovacuum_vacuum_threshold">
|
|
<term><varname>autovacuum_vacuum_threshold</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>autovacuum_vacuum_threshold</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the minimum number of updated or deleted tuples needed
|
|
to trigger a <command>VACUUM</> in any one table.
|
|
The default is 50 tuples.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
This setting can be overridden for individual tables by entries in
|
|
<structname>pg_autovacuum</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-autovacuum-analyze-threshold" xreflabel="autovacuum_analyze_threshold">
|
|
<term><varname>autovacuum_analyze_threshold</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>autovacuum_analyze_threshold</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the minimum number of inserted, updated or deleted tuples
|
|
needed to trigger an <command>ANALYZE</> in any one table.
|
|
The default is 50 tuples.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
This setting can be overridden for individual tables by entries in
|
|
<structname>pg_autovacuum</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-autovacuum-vacuum-scale-factor" xreflabel="autovacuum_vacuum_scale_factor">
|
|
<term><varname>autovacuum_vacuum_scale_factor</varname> (<type>floating point</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>autovacuum_vacuum_scale_factor</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies a fraction of the table size to add to
|
|
<varname>autovacuum_vacuum_threshold</varname>
|
|
when deciding whether to trigger a <command>VACUUM</>.
|
|
The default is 0.2 (20% of table size).
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
This setting can be overridden for individual tables by entries in
|
|
<structname>pg_autovacuum</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-autovacuum-analyze-scale-factor" xreflabel="autovacuum_analyze_scale_factor">
|
|
<term><varname>autovacuum_analyze_scale_factor</varname> (<type>floating point</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>autovacuum_analyze_scale_factor</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies a fraction of the table size to add to
|
|
<varname>autovacuum_analyze_threshold</varname>
|
|
when deciding whether to trigger an <command>ANALYZE</>.
|
|
The default is 0.1 (10% of table size).
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
This setting can be overridden for individual tables by entries in
|
|
<structname>pg_autovacuum</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-autovacuum-freeze-max-age" xreflabel="autovacuum_freeze_max_age">
|
|
<term><varname>autovacuum_freeze_max_age</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>autovacuum_freeze_max_age</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the maximum age (in transactions) that a table's
|
|
<structname>pg_class</>.<structfield>relfrozenxid</> field can
|
|
attain before a <command>VACUUM</> operation is forced to prevent
|
|
transaction ID wraparound within the table. Note that the system
|
|
will launch autovacuum processes to prevent wraparound even when
|
|
autovacuum is otherwise disabled.
|
|
The default is 200 million transactions.
|
|
This parameter can only be set at server start, but the setting
|
|
can be reduced for individual tables by entries in
|
|
<structname>pg_autovacuum</>.
|
|
For more information see <xref linkend="vacuum-for-wraparound">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-autovacuum-vacuum-cost-delay" xreflabel="autovacuum_vacuum_cost_delay">
|
|
<term><varname>autovacuum_vacuum_cost_delay</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>autovacuum_vacuum_cost_delay</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the cost delay value that will be used in automatic
|
|
<command>VACUUM</> operations. If <literal>-1</> is
|
|
specified, the regular
|
|
<xref linkend="guc-vacuum-cost-delay"> value will be used.
|
|
The default value is 20 milliseconds.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
This setting can be overridden for individual tables by entries in
|
|
<structname>pg_autovacuum</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-autovacuum-vacuum-cost-limit" xreflabel="autovacuum_vacuum_cost_limit">
|
|
<term><varname>autovacuum_vacuum_cost_limit</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>autovacuum_vacuum_cost_limit</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the cost limit value that will be used in automatic
|
|
<command>VACUUM</> operations. If <literal>-1</> is specified (which is the
|
|
default), the regular
|
|
<xref linkend="guc-vacuum-cost-limit"> value will be used. Note that
|
|
the value is distributed proportionally among the running autovacuum
|
|
workers, if there is more than one, so that the sum of the limits of
|
|
each worker never exceeds the limit on this variable.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
This setting can be overridden for individual tables by entries in
|
|
<structname>pg_autovacuum</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-client">
|
|
<title>Client Connection Defaults</title>
|
|
|
|
<sect2 id="runtime-config-client-statement">
|
|
<title>Statement Behavior</title>
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-search-path" xreflabel="search_path">
|
|
<term><varname>search_path</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>search_path</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm><primary>path</><secondary>for schemas</></>
|
|
<listitem>
|
|
<para>
|
|
This variable specifies the order in which schemas are searched
|
|
when an object (table, data type, function, etc.) is referenced by a
|
|
simple name with no schema component. When there are objects of
|
|
identical names in different schemas, the one found first
|
|
in the search path is used. An object that is not in any of the
|
|
schemas in the search path can only be referenced by specifying
|
|
its containing schema with a qualified (dotted) name.
|
|
</para>
|
|
|
|
<para>
|
|
The value for <varname>search_path</varname> has to be a comma-separated
|
|
list of schema names. If one of the list items is
|
|
the special value <literal>$user</literal>, then the schema
|
|
having the name returned by <function>SESSION_USER</> is substituted, if there
|
|
is such a schema. (If not, <literal>$user</literal> is ignored.)
|
|
</para>
|
|
|
|
<para>
|
|
The system catalog schema, <literal>pg_catalog</>, is always
|
|
searched, whether it is mentioned in the path or not. If it is
|
|
mentioned in the path then it will be searched in the specified
|
|
order. If <literal>pg_catalog</> is not in the path then it will
|
|
be searched <emphasis>before</> searching any of the path items.
|
|
</para>
|
|
|
|
<para>
|
|
Likewise, the current session's temporary-table schema,
|
|
<literal>pg_temp_<replaceable>nnn</></>, is always searched if it
|
|
exists. It can be explicitly listed in the path by using the
|
|
alias <literal>pg_temp</>. If it is not listed in the path then
|
|
it is searched first (before even <literal>pg_catalog</>). However,
|
|
the temporary schema is only searched for relation (table, view,
|
|
sequence, etc) and data type names. It will never be searched for
|
|
function or operator names.
|
|
</para>
|
|
|
|
<para>
|
|
When objects are created without specifying a particular target
|
|
schema, they will be placed in the first schema listed
|
|
in the search path. An error is reported if the search path is
|
|
empty.
|
|
</para>
|
|
|
|
<para>
|
|
The default value for this parameter is
|
|
<literal>'"$user", public'</literal> (where the second part will be
|
|
ignored if there is no schema named <literal>public</>).
|
|
This supports shared use of a database (where no users
|
|
have private schemas, and all share use of <literal>public</>),
|
|
private per-user schemas, and combinations of these. Other
|
|
effects can be obtained by altering the default search path
|
|
setting, either globally or per-user.
|
|
</para>
|
|
|
|
<para>
|
|
The current effective value of the search path can be examined
|
|
via the <acronym>SQL</acronym> function
|
|
<function>current_schemas()</>. This is not quite the same as
|
|
examining the value of <varname>search_path</varname>, since
|
|
<function>current_schemas()</> shows how the requests
|
|
appearing in <varname>search_path</varname> were resolved.
|
|
</para>
|
|
|
|
<para>
|
|
For more information on schema handling, see <xref linkend="ddl-schemas">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-default-tablespace" xreflabel="default_tablespace">
|
|
<term><varname>default_tablespace</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>default_tablespace</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm><primary>tablespace</><secondary>default</></>
|
|
<listitem>
|
|
<para>
|
|
This variable specifies the default tablespace in which to create
|
|
objects (tables and indexes) when a <command>CREATE</> command does
|
|
not explicitly specify a tablespace.
|
|
</para>
|
|
|
|
<para>
|
|
The value is either the name of a tablespace, or an empty string
|
|
to specify using the default tablespace of the current database.
|
|
If the value does not match the name of any existing tablespace,
|
|
<productname>PostgreSQL</> will automatically use the default
|
|
tablespace of the current database. If a nondefault tablespace
|
|
is specified, the user must have <literal>CREATE</> privilege
|
|
for it, or creation attempts will fail.
|
|
</para>
|
|
|
|
<para>
|
|
This variable is not used for temporary tables; for them,
|
|
<xref linkend="guc-temp-tablespaces"> is consulted instead.
|
|
</para>
|
|
|
|
<para>
|
|
For more information on tablespaces,
|
|
see <xref linkend="manage-ag-tablespaces">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-temp-tablespaces" xreflabel="temp_tablespaces">
|
|
<term><varname>temp_tablespaces</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>temp_tablespaces</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm><primary>tablespace</><secondary>temporary</></>
|
|
<listitem>
|
|
<para>
|
|
This variable specifies tablespace(s) in which to create temporary
|
|
objects (temp tables and indexes on temp tables) when a
|
|
<command>CREATE</> command does not explicitly specify a tablespace.
|
|
Temporary files for purposes such as sorting large data sets
|
|
are also created in these tablespace(s).
|
|
</para>
|
|
|
|
<para>
|
|
The value is a list of names of tablespaces. When there is more than
|
|
one name in the list, <productname>PostgreSQL</> chooses a random
|
|
member of the list each time a temporary object is to be created;
|
|
except that within a transaction, successively created temporary
|
|
objects are placed in successive tablespaces from the list.
|
|
If the selected element of the list is an empty string,
|
|
<productname>PostgreSQL</> will automatically use the default
|
|
tablespace of the current database instead.
|
|
</para>
|
|
|
|
<para>
|
|
When <varname>temp_tablespaces</> is set interactively, specifying a
|
|
nonexistent tablespace is an error, as is specifying a tablespace for
|
|
which the user does not have <literal>CREATE</> privilege. However,
|
|
when using a previously set value, nonexistent tablespaces are
|
|
ignored, as are tablespaces for which the user lacks
|
|
<literal>CREATE</> privilege. In particular, this rule applies when
|
|
using a value set in <filename>postgresql.conf</>.
|
|
</para>
|
|
|
|
<para>
|
|
The default value is an empty string, which results in all temporary
|
|
objects being created in the default tablespace of the current
|
|
database.
|
|
</para>
|
|
|
|
<para>
|
|
See also <xref linkend="guc-default-tablespace">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-check-function-bodies" xreflabel="check_function_bodies">
|
|
<term><varname>check_function_bodies</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>check_function_bodies</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This parameter is normally on. When set to <literal>off</>, it
|
|
disables validation of the function body string during <xref
|
|
linkend="sql-createfunction"
|
|
endterm="sql-createfunction-title">. Disabling validation is
|
|
occasionally useful to avoid problems such as forward references
|
|
when restoring function definitions from a dump.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-default-transaction-isolation" xreflabel="default_transaction_isolation">
|
|
<indexterm>
|
|
<primary>transaction isolation level</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>default_transaction_isolation</> configuration parameter</primary>
|
|
</indexterm>
|
|
<term><varname>default_transaction_isolation</varname> (<type>string</type>)</term>
|
|
<listitem>
|
|
<para>
|
|
Each SQL transaction has an isolation level, which can be
|
|
either <quote>read uncommitted</quote>, <quote>read
|
|
committed</quote>, <quote>repeatable read</quote>, or
|
|
<quote>serializable</quote>. This parameter controls the
|
|
default isolation level of each new transaction. The default
|
|
is <quote>read committed</quote>.
|
|
</para>
|
|
|
|
<para>
|
|
Consult <xref linkend="mvcc"> and <xref
|
|
linkend="sql-set-transaction"
|
|
endterm="sql-set-transaction-title"> for more information.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-default-transaction-read-only" xreflabel="default_transaction_read_only">
|
|
<indexterm>
|
|
<primary>read-only transaction</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>default_transaction_read_only</> configuration parameter</primary>
|
|
</indexterm>
|
|
|
|
<term><varname>default_transaction_read_only</varname> (<type>boolean</type>)</term>
|
|
<listitem>
|
|
<para>
|
|
A read-only SQL transaction cannot alter non-temporary tables.
|
|
This parameter controls the default read-only status of each new
|
|
transaction. The default is <literal>off</> (read/write).
|
|
</para>
|
|
|
|
<para>
|
|
Consult <xref linkend="sql-set-transaction"
|
|
endterm="sql-set-transaction-title"> for more information.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-session-replication-role" xreflabel="session_replication_role">
|
|
<term><varname>session_replication_role</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>session_replication_role</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Controls firing of replication-related triggers and rules for the
|
|
current session. Setting this variable requires
|
|
superuser privilege and results in discarding any previously cached
|
|
query plans. Possible values are <literal>origin</> (the default),
|
|
<literal>replica</> and <literal>local</>.
|
|
See <xref linkend="sql-altertable" endterm="sql-altertable-title"> for
|
|
more information.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-statement-timeout" xreflabel="statement_timeout">
|
|
<term><varname>statement_timeout</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>statement_timeout</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Abort any statement that takes over the specified number of
|
|
milliseconds, starting from the time the command arrives at the server
|
|
from the client. If <varname>log_min_error_statement</> is set to
|
|
<literal>ERROR</> or lower, the statement that timed out will also be
|
|
logged. A value of zero (the default) turns off the
|
|
limitation.
|
|
</para>
|
|
|
|
<para>
|
|
Setting <varname>statement_timeout</> in
|
|
<filename>postgresql.conf</> is not recommended because it
|
|
affects all sessions.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-vacuum-freeze-min-age" xreflabel="vacuum_freeze_min_age">
|
|
<term><varname>vacuum_freeze_min_age</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>vacuum_freeze_min_age</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Specifies the cutoff age (in transactions) that <command>VACUUM</>
|
|
should use to decide whether to replace transaction IDs with
|
|
<literal>FrozenXID</> while scanning a table.
|
|
The default is 100 million transactions. Although
|
|
users can set this value anywhere from zero to one billion,
|
|
<command>VACUUM</> will silently limit the effective value to half
|
|
the value of <xref linkend="guc-autovacuum-freeze-max-age">, so
|
|
that there is not an unreasonably short time between forced
|
|
autovacuums. For more information see <xref
|
|
linkend="vacuum-for-wraparound">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-xmlbinary" xreflabel="xmlbinary">
|
|
<term><varname>xmlbinary</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>xmlbinary</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets how binary values are to be encoded in XML. This applies
|
|
for example when <type>bytea</type> values are converted to
|
|
XML by the functions <function>xmlelement</function> or
|
|
<function>xmlforest</function>. Possible values are
|
|
<literal>base64</literal> and <literal>hex</literal>, which
|
|
are both defined in the XML Schema standard. The default is
|
|
<literal>base64</literal>. For further information about
|
|
XML-related functions, see <xref linkend="functions-xml">.
|
|
</para>
|
|
|
|
<para>
|
|
The actual choice here is mostly a matter of taste,
|
|
constrained only by possible restrictions in client
|
|
applications. Both methods support all possible values,
|
|
although the hex encoding will be somewhat larger than the
|
|
base64 encoding.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-xmloption" xreflabel="xmloption">
|
|
<term><varname>xmloption</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>xmloption</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>SET XML OPTION</></primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>XML option</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets whether <literal>DOCUMENT</literal> or
|
|
<literal>CONTENT</literal> is implicit when converting between
|
|
XML and character string values. See <xref
|
|
linkend="datatype-xml"> for a description of this. Valid
|
|
values are <literal>DOCUMENT</literal> and
|
|
<literal>CONTENT</literal>. The default is
|
|
<literal>CONTENT</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
According to the SQL standard, the command to set this option is
|
|
<synopsis>
|
|
SET XML OPTION { DOCUMENT | CONTENT };
|
|
</synopsis>
|
|
This syntax is also available in PostgreSQL.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
<sect2 id="runtime-config-client-format">
|
|
<title>Locale and Formatting</title>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-datestyle" xreflabel="DateStyle">
|
|
<term><varname>DateStyle</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>DateStyle</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the display format for date and time values, as well as the
|
|
rules for interpreting ambiguous date input values. For
|
|
historical reasons, this variable contains two independent
|
|
components: the output format specification (<literal>ISO</>,
|
|
<literal>Postgres</>, <literal>SQL</>, or <literal>German</>)
|
|
and the input/output specification for year/month/day ordering
|
|
(<literal>DMY</>, <literal>MDY</>, or <literal>YMD</>). These
|
|
can be set separately or together. The keywords <literal>Euro</>
|
|
and <literal>European</> are synonyms for <literal>DMY</>; the
|
|
keywords <literal>US</>, <literal>NonEuro</>, and
|
|
<literal>NonEuropean</> are synonyms for <literal>MDY</>. See
|
|
<xref linkend="datatype-datetime"> for more information. The
|
|
built-in default is <literal>ISO, MDY</>, but
|
|
<application>initdb</application> will initialize the
|
|
configuration file with a setting that corresponds to the
|
|
behavior of the chosen <varname>lc_time</varname> locale.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-timezone" xreflabel="timezone">
|
|
<term><varname>timezone</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>timezone</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm><primary>time zone</></>
|
|
<listitem>
|
|
<para>
|
|
Sets the time zone for displaying and interpreting time stamps.
|
|
The default is <literal>unknown</>, which means to use whatever
|
|
the system environment specifies as the time zone. See <xref
|
|
linkend="datatype-timezones"> for more
|
|
information.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-timezone-abbreviations" xreflabel="timezone_abbreviations">
|
|
<term><varname>timezone_abbreviations</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>timezone_abbreviations</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm><primary>time zone names</></>
|
|
<listitem>
|
|
<para>
|
|
Sets the collection of time zone abbreviations that will be accepted
|
|
by the server for datetime input. The default is <literal>'Default'</>,
|
|
which is a collection that works in most of the world; there are
|
|
also 'Australia' and 'India', and other collections can be defined
|
|
for a particular installation. See <xref
|
|
linkend="datetime-appendix"> for more information.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-extra-float-digits" xreflabel="extra_float_digits">
|
|
<indexterm>
|
|
<primary>significant digits</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>floating-point</primary>
|
|
<secondary>display</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>extra_float_digits</> configuration parameter</primary>
|
|
</indexterm>
|
|
|
|
<term><varname>extra_float_digits</varname> (<type>integer</type>)</term>
|
|
<listitem>
|
|
<para>
|
|
This parameter adjusts the number of digits displayed for
|
|
floating-point values, including <type>float4</>, <type>float8</>,
|
|
and geometric data types. The parameter value is added to the
|
|
standard number of digits (<literal>FLT_DIG</> or <literal>DBL_DIG</>
|
|
as appropriate). The value can be set as high as 2, to include
|
|
partially-significant digits; this is especially useful for dumping
|
|
float data that needs to be restored exactly. Or it can be set
|
|
negative to suppress unwanted digits.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-client-encoding" xreflabel="client_encoding">
|
|
<term><varname>client_encoding</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>client_encoding</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm><primary>character set</></>
|
|
<listitem>
|
|
<para>
|
|
Sets the client-side encoding (character set).
|
|
The default is to use the database encoding.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-lc-messages" xreflabel="lc_messages">
|
|
<term><varname>lc_messages</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>lc_messages</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the language in which messages are displayed. Acceptable
|
|
values are system-dependent; see <xref linkend="locale"> for
|
|
more information. If this variable is set to the empty string
|
|
(which is the default) then the value is inherited from the
|
|
execution environment of the server in a system-dependent way.
|
|
</para>
|
|
|
|
<para>
|
|
On some systems, this locale category does not exist. Setting
|
|
this variable will still work, but there will be no effect.
|
|
Also, there is a chance that no translated messages for the
|
|
desired language exist. In that case you will continue to see
|
|
the English messages.
|
|
</para>
|
|
|
|
<para>
|
|
Only superusers can change this setting, because it affects the
|
|
messages sent to the server log as well as to the client.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-lc-monetary" xreflabel="lc_monetary">
|
|
<term><varname>lc_monetary</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>lc_monetary</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the locale to use for formatting monetary amounts, for
|
|
example with the <function>to_char</function> family of
|
|
functions. Acceptable values are system-dependent; see <xref
|
|
linkend="locale"> for more information. If this variable is
|
|
set to the empty string (which is the default) then the value
|
|
is inherited from the execution environment of the server in a
|
|
system-dependent way.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-lc-numeric" xreflabel="lc_numeric">
|
|
<term><varname>lc_numeric</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>lc_numeric</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the locale to use for formatting numbers, for example
|
|
with the <function>to_char</function> family of
|
|
functions. Acceptable values are system-dependent; see <xref
|
|
linkend="locale"> for more information. If this variable is
|
|
set to the empty string (which is the default) then the value
|
|
is inherited from the execution environment of the server in a
|
|
system-dependent way.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-lc-time" xreflabel="lc_time">
|
|
<term><varname>lc_time</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>lc_time</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Sets the locale to use for formatting dates and times, for example
|
|
with the <function>to_char</function> family of
|
|
functions. Acceptable values are system-dependent; see <xref
|
|
linkend="locale"> for more information. If this variable is
|
|
set to the empty string (which is the default) then the value
|
|
is inherited from the execution environment of the server in a
|
|
system-dependent way.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-default-text-search-config" xreflabel="default_text_search_config">
|
|
<term><varname>default_text_search_config</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>default_text_search_config</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Selects the text search configuration that is used by those variants
|
|
of the text search functions that do not have an explicit argument
|
|
specifying the configuration.
|
|
See <xref linkend="textsearch"> for further information.
|
|
The built-in default is <literal>pg_catalog.simple</>, but
|
|
<application>initdb</application> will initialize the
|
|
configuration file with a setting that corresponds to the
|
|
chosen <varname>lc_ctype</varname> locale, if a configuration
|
|
matching that locale can be identified.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
|
|
</sect2>
|
|
<sect2 id="runtime-config-client-other">
|
|
<title>Other Defaults</title>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-dynamic-library-path" xreflabel="dynamic_library_path">
|
|
<term><varname>dynamic_library_path</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>dynamic_library_path</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm><primary>dynamic loading</></>
|
|
<listitem>
|
|
<para>
|
|
If a dynamically loadable module needs to be opened and the
|
|
file name specified in the <command>CREATE FUNCTION</command> or
|
|
<command>LOAD</command> command
|
|
does not have a directory component (i.e. the
|
|
name does not contain a slash), the system will search this
|
|
path for the required file.
|
|
</para>
|
|
|
|
<para>
|
|
The value for <varname>dynamic_library_path</varname> has to be a
|
|
list of absolute directory paths separated by colons (or semi-colons
|
|
on Windows). If a list element starts
|
|
with the special string <literal>$libdir</literal>, the
|
|
compiled-in <productname>PostgreSQL</productname> package
|
|
library directory is substituted for <literal>$libdir</literal>. This
|
|
is where the modules provided by the standard
|
|
<productname>PostgreSQL</productname> distribution are installed.
|
|
(Use <literal>pg_config --pkglibdir</literal> to find out the name of
|
|
this directory.) For example:
|
|
<programlisting>
|
|
dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
|
|
</programlisting>
|
|
or, in a Windows environment:
|
|
<programlisting>
|
|
dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The default value for this parameter is
|
|
<literal>'$libdir'</literal>. If the value is set to an empty
|
|
string, the automatic path search is turned off.
|
|
</para>
|
|
|
|
<para>
|
|
This parameter can be changed at run time by superusers, but a
|
|
setting done that way will only persist until the end of the
|
|
client connection, so this method should be reserved for
|
|
development purposes. The recommended way to set this parameter
|
|
is in the <filename>postgresql.conf</filename> configuration
|
|
file.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-gin-fuzzy-search-limit" xreflabel="gin_fuzzy_search_limit">
|
|
<term><varname>gin_fuzzy_search_limit</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>gin_fuzzy_search_limit</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Soft upper limit of the size of the set returned by GIN index. For more
|
|
information see <xref linkend="gin-tips">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-local-preload-libraries" xreflabel="local_preload_libraries">
|
|
<term><varname>local_preload_libraries</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>local_preload_libraries</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><filename>$libdir/plugins</></primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This variable specifies one or more shared libraries that are
|
|
to be preloaded at connection start. If more than one library
|
|
is to be loaded, separate their names with commas.
|
|
This parameter cannot be changed after the start of a particular
|
|
session.
|
|
</para>
|
|
|
|
<para>
|
|
Because this is not a superuser-only option, the libraries
|
|
that can be loaded are restricted to those appearing in the
|
|
<filename>plugins</> subdirectory of the installation's
|
|
standard library directory. (It is the database administrator's
|
|
responsibility to ensure that only <quote>safe</> libraries
|
|
are installed there.) Entries in <varname>local_preload_libraries</>
|
|
can specify this directory explicitly, for example
|
|
<literal>$libdir/plugins/mylib</literal>, or just specify
|
|
the library name — <literal>mylib</literal> would have
|
|
the same effect as <literal>$libdir/plugins/mylib</literal>.
|
|
</para>
|
|
|
|
<para>
|
|
There is no performance advantage to loading a library at session
|
|
start rather than when it is first used. Rather, the intent of
|
|
this feature is to allow debugging or performance-measurement
|
|
libraries to be loaded into specific sessions without an explicit
|
|
<command>LOAD</> command being given. For example, debugging could
|
|
be enabled for all sessions under a given user name by setting
|
|
this parameter with <command>ALTER USER SET</>.
|
|
</para>
|
|
|
|
<para>
|
|
If a specified library is not found,
|
|
the connection attempt will fail.
|
|
</para>
|
|
|
|
<para>
|
|
Every PostgreSQL-supported library has a <quote>magic
|
|
block</> that is checked to guarantee compatibility.
|
|
For this reason, non-PostgreSQL libraries cannot be
|
|
loaded in this way.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-locks">
|
|
<title>Lock Management</title>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-deadlock-timeout" xreflabel="deadlock_timeout">
|
|
<indexterm>
|
|
<primary>deadlock</primary>
|
|
<secondary>timeout during</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>timeout</primary>
|
|
<secondary>deadlock</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary><varname>deadlock_timeout</> configuration parameter</primary>
|
|
</indexterm>
|
|
|
|
<term><varname>deadlock_timeout</varname> (<type>integer</type>)</term>
|
|
<listitem>
|
|
<para>
|
|
This is the amount of time, in milliseconds, to wait on a lock
|
|
before checking to see if there is a deadlock condition. The
|
|
check for deadlock is relatively slow, so the server doesn't run
|
|
it every time it waits for a lock. We optimistically assume
|
|
that deadlocks are not common in production applications and
|
|
just wait on the lock for a while before starting the check for a
|
|
deadlock. Increasing this value reduces the amount of time
|
|
wasted in needless deadlock checks, but slows down reporting of
|
|
real deadlock errors. The default is one second (<literal>1s</>),
|
|
which is probably about the smallest value you would want in
|
|
practice. On a heavily loaded server you might want to raise it.
|
|
Ideally the setting should exceed your typical transaction time,
|
|
so as to improve the odds that a lock will be released before
|
|
the waiter decides to check for deadlock.
|
|
</para>
|
|
|
|
<para>
|
|
When <xref linkend="guc-log-lock-waits"> is set,
|
|
this parameter also determines the length of time to wait before
|
|
a log message is issued about the lock wait. If you are trying
|
|
to investigate locking delays you might want to set a shorter than
|
|
normal <varname>deadlock_timeout</varname>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-max-locks-per-transaction" xreflabel="max_locks_per_transaction">
|
|
<term><varname>max_locks_per_transaction</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>max_locks_per_transaction</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The shared lock table is created to track locks on
|
|
<varname>max_locks_per_transaction</varname> * (<xref
|
|
linkend="guc-max-connections"> + <xref
|
|
linkend="guc-max-prepared-transactions">) objects (e.g. tables);
|
|
hence, no more than this many distinct objects can be locked at
|
|
any one time. This parameter controls the average number of object
|
|
locks allocated for each transaction; individual transactions
|
|
can lock more objects as long as the locks of all transactions
|
|
fit in the lock table. This is <emphasis>not</> the number of
|
|
rows that can be locked; that value is unlimited. The default,
|
|
64, has historically proven sufficient, but you might need to
|
|
raise this value if you have clients that touch many different
|
|
tables in a single transaction. This parameter can only be set at
|
|
server start.
|
|
</para>
|
|
|
|
<para>
|
|
Increasing this parameter might cause <productname>PostgreSQL</>
|
|
to request more <systemitem class="osname">System V</> shared
|
|
memory than your operating system's default configuration
|
|
allows. See <xref linkend="sysvipc"> for information on how to
|
|
adjust those parameters, if necessary.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-compatible">
|
|
<title>Version and Platform Compatibility</title>
|
|
|
|
<sect2 id="runtime-config-compatible-version">
|
|
<title>Previous PostgreSQL Versions</title>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-add-missing-from" xreflabel="add_missing_from">
|
|
<term><varname>add_missing_from</varname> (<type>boolean</type>)</term>
|
|
<indexterm><primary>FROM</><secondary>missing</></>
|
|
<indexterm>
|
|
<primary><varname>add_missing_from</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When on, tables that are referenced by a query will be
|
|
automatically added to the <literal>FROM</> clause if not
|
|
already present. This behavior does not comply with the SQL
|
|
standard and many people dislike it because it can mask mistakes
|
|
(such as referencing a table where you should have referenced
|
|
its alias). The default is <literal>off</>. This variable can be
|
|
enabled for compatibility with releases of
|
|
<productname>PostgreSQL</> prior to 8.1, where this behavior was
|
|
allowed by default.
|
|
</para>
|
|
|
|
<para>
|
|
Note that even when this variable is enabled, a warning
|
|
message will be emitted for each implicit <literal>FROM</>
|
|
entry referenced by a query. Users are encouraged to update
|
|
their applications to not rely on this behavior, by adding all
|
|
tables referenced by a query to the query's <literal>FROM</>
|
|
clause (or its <literal>USING</> clause in the case of
|
|
<command>DELETE</>).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-array-nulls" xreflabel="array_nulls">
|
|
<term><varname>array_nulls</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>array_nulls</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This controls whether the array input parser recognizes
|
|
unquoted <literal>NULL</> as specifying a null array element.
|
|
By default, this is <literal>on</>, allowing array values containing
|
|
null values to be entered. However, <productname>PostgreSQL</> versions
|
|
before 8.2 did not support null values in arrays, and therefore would
|
|
treat <literal>NULL</> as specifying a normal array element with
|
|
the string value <quote>NULL</>. For backwards compatibility with
|
|
applications that require the old behavior, this variable can be
|
|
turned <literal>off</>.
|
|
</para>
|
|
|
|
<para>
|
|
Note that it is possible to create array values containing null values
|
|
even when this variable is <literal>off</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-backslash-quote" xreflabel="backslash_quote">
|
|
<term><varname>backslash_quote</varname> (<type>string</type>)</term>
|
|
<indexterm><primary>strings</><secondary>backslash quotes</></>
|
|
<indexterm>
|
|
<primary><varname>backslash_quote</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This controls whether a quote mark can be represented by
|
|
<literal>\'</> in a string literal. The preferred, SQL-standard way
|
|
to represent a quote mark is by doubling it (<literal>''</>) but
|
|
<productname>PostgreSQL</> has historically also accepted
|
|
<literal>\'</>. However, use of <literal>\'</> creates security risks
|
|
because in some client character set encodings, there are multibyte
|
|
characters in which the last byte is numerically equivalent to ASCII
|
|
<literal>\</>. If client-side code does escaping incorrectly then a
|
|
SQL-injection attack is possible. This risk can be prevented by
|
|
making the server reject queries in which a quote mark appears to be
|
|
escaped by a backslash.
|
|
The allowed values of <varname>backslash_quote</> are
|
|
<literal>on</> (allow <literal>\'</> always),
|
|
<literal>off</> (reject always), and
|
|
<literal>safe_encoding</> (allow only if client encoding does not
|
|
allow ASCII <literal>\</> within a multibyte character).
|
|
<literal>safe_encoding</> is the default setting.
|
|
</para>
|
|
|
|
<para>
|
|
Note that in a standard-conforming string literal, <literal>\</> just
|
|
means <literal>\</> anyway. This parameter affects the handling of
|
|
non-standard-conforming literals, including
|
|
escape string syntax (<literal>E'...'</>).
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-default-with-oids" xreflabel="default_with_oids">
|
|
<term><varname>default_with_oids</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>default_with_oids</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This controls whether <command>CREATE TABLE</command> and
|
|
<command>CREATE TABLE AS</command> include an OID column in
|
|
newly-created tables, if neither <literal>WITH OIDS</literal>
|
|
nor <literal>WITHOUT OIDS</literal> is specified. It also
|
|
determines whether OIDs will be included in tables created by
|
|
<command>SELECT INTO</command>. In <productname>PostgreSQL</>
|
|
8.1 <varname>default_with_oids</> is <literal>off</> by default; in
|
|
prior versions of <productname>PostgreSQL</productname>, it
|
|
was on by default.
|
|
</para>
|
|
|
|
<para>
|
|
The use of OIDs in user tables is considered deprecated, so
|
|
most installations should leave this variable disabled.
|
|
Applications that require OIDs for a particular table should
|
|
specify <literal>WITH OIDS</literal> when creating the
|
|
table. This variable can be enabled for compatibility with old
|
|
applications that do not follow this behavior.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-escape-string-warning" xreflabel="escape_string_warning">
|
|
<term><varname>escape_string_warning</varname> (<type>boolean</type>)</term>
|
|
<indexterm><primary>strings</><secondary>escape warning</></>
|
|
<indexterm>
|
|
<primary><varname>escape_string_warning</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When on, a warning is issued if a backslash (<literal>\</>)
|
|
appears in an ordinary string literal (<literal>'...'</>
|
|
syntax) and <varname>standard_conforming_strings</varname> is off.
|
|
The default is <literal>on</>.
|
|
</para>
|
|
<para>
|
|
Applications that wish to use backslash as escape should be
|
|
modified to use escape string syntax (<literal>E'...'</>),
|
|
because the default behavior of ordinary strings will change
|
|
in a future release for SQL compatibility. This variable can
|
|
be enabled to help detect applications that will break.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-regex-flavor" xreflabel="regex_flavor">
|
|
<term><varname>regex_flavor</varname> (<type>string</type>)</term>
|
|
<indexterm><primary>regular expressions</></>
|
|
<indexterm>
|
|
<primary><varname>regex_flavor</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
The regular expression <quote>flavor</> can be set to
|
|
<literal>advanced</>, <literal>extended</>, or <literal>basic</>.
|
|
The default is <literal>advanced</>. The <literal>extended</>
|
|
setting might be useful for exact backwards compatibility with
|
|
pre-7.4 releases of <productname>PostgreSQL</>. See
|
|
<xref linkend="posix-syntax-details"> for details.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-sql-inheritance" xreflabel="sql_inheritance">
|
|
<term><varname>sql_inheritance</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>sql_inheritance</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm><primary>inheritance</></>
|
|
<listitem>
|
|
<para>
|
|
This controls the inheritance semantics. If turned <literal>off</>,
|
|
subtables are not included by various commands by default; basically
|
|
an implied <literal>ONLY</literal> key word. This was added for
|
|
compatibility with releases prior to 7.1. See
|
|
<xref linkend="ddl-inherit"> for more information.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-standard-conforming-strings" xreflabel="standard_conforming_strings">
|
|
<term><varname>standard_conforming_strings</varname> (<type>boolean</type>)</term>
|
|
<indexterm><primary>strings</><secondary>standard conforming</></>
|
|
<indexterm>
|
|
<primary><varname>standard_conforming_strings</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This controls whether ordinary string literals
|
|
(<literal>'...'</>) treat backslashes literally, as specified in
|
|
the SQL standard.
|
|
The default is currently <literal>off</>, causing
|
|
<productname>PostgreSQL</productname> to have its historical
|
|
behavior of treating backslashes as escape characters.
|
|
The default will change to <literal>on</> in a future release
|
|
to improve compatibility with the standard.
|
|
Applications can check this
|
|
parameter to determine how string literals will be processed.
|
|
The presence of this parameter can also be taken as an indication
|
|
that the escape string syntax (<literal>E'...'</>) is supported.
|
|
Escape string syntax should be used if an application desires
|
|
backslashes to be treated as escape characters.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-synchronize-seqscans" xreflabel="synchronize_seqscans">
|
|
<term><varname>synchronize_seqscans</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>synchronize_seqscans</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This allows sequential scans of large tables to synchronize with each
|
|
other, so that concurrent scans read the same block at about the
|
|
same time and hence share the I/O workload. When this is enabled,
|
|
a scan might start in the middle of the table and then <quote>wrap
|
|
around</> the end to cover all rows, so as to synchronize with the
|
|
activity of scans already in progress. This can result in
|
|
unpredictable changes in the row ordering returned by queries that
|
|
have no <literal>ORDER BY</> clause. Setting this parameter to
|
|
<literal>off</> ensures the pre-8.3 behavior in which a sequential
|
|
scan always starts from the beginning of the table. The default
|
|
is <literal>on</>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
<sect2 id="runtime-config-compatible-clients">
|
|
<title>Platform and Client Compatibility</title>
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-transform-null-equals" xreflabel="transform_null_equals">
|
|
<term><varname>transform_null_equals</varname> (<type>boolean</type>)</term>
|
|
<indexterm><primary>IS NULL</></>
|
|
<indexterm>
|
|
<primary><varname>transform_null_equals</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
When on, expressions of the form <literal><replaceable>expr</> =
|
|
NULL</literal> (or <literal>NULL =
|
|
<replaceable>expr</></literal>) are treated as
|
|
<literal><replaceable>expr</> IS NULL</literal>, that is, they
|
|
return true if <replaceable>expr</> evaluates to the null value,
|
|
and false otherwise. The correct SQL-spec-compliant behavior of
|
|
<literal><replaceable>expr</> = NULL</literal> is to always
|
|
return null (unknown). Therefore this parameter defaults to
|
|
<literal>off</>.
|
|
</para>
|
|
|
|
<para>
|
|
However, filtered forms in <productname>Microsoft
|
|
Access</productname> generate queries that appear to use
|
|
<literal><replaceable>expr</> = NULL</literal> to test for
|
|
null values, so if you use that interface to access the database you
|
|
might want to turn this option on. Since expressions of the
|
|
form <literal><replaceable>expr</> = NULL</literal> always
|
|
return the null value (using the correct interpretation) they are not
|
|
very useful and do not appear often in normal applications, so
|
|
this option does little harm in practice. But new users are
|
|
frequently confused about the semantics of expressions
|
|
involving null values, so this option is not on by default.
|
|
</para>
|
|
|
|
<para>
|
|
Note that this option only affects the exact form <literal>= NULL</>,
|
|
not other comparison operators or other expressions
|
|
that are computationally equivalent to some expression
|
|
involving the equals operator (such as <literal>IN</literal>).
|
|
Thus, this option is not a general fix for bad programming.
|
|
</para>
|
|
|
|
<para>
|
|
Refer to <xref linkend="functions-comparison"> for related information.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-preset">
|
|
<title>Preset Options</title>
|
|
|
|
<para>
|
|
The following <quote>parameters</> are read-only, and are determined
|
|
when <productname>PostgreSQL</productname> is compiled or when it is
|
|
installed. As such, they have been excluded from the sample
|
|
<filename>postgresql.conf</> file. These options report
|
|
various aspects of <productname>PostgreSQL</productname> behavior
|
|
that might be of interest to certain applications, particularly
|
|
administrative front-ends.
|
|
</para>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-block-size" xreflabel="block_size">
|
|
<term><varname>block_size</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>block_size</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Reports the size of a disk block. It is determined by the value
|
|
of <literal>BLCKSZ</> when building the server. The default
|
|
value is 8192 bytes. The meaning of some configuration
|
|
variables (such as <xref linkend="guc-shared-buffers">) is
|
|
influenced by <varname>block_size</varname>. See <xref
|
|
linkend="runtime-config-resource"> for information.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-integer-datetimes" xreflabel="integer_datetimes">
|
|
<term><varname>integer_datetimes</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>integer_datetimes</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Reports whether <productname>PostgreSQL</> was built with
|
|
support for 64-bit-integer dates and times. This can be
|
|
disabled by configuring with <literal>--disable-integer-datetimes</>
|
|
when building <productname>PostgreSQL</>. The default value is
|
|
<literal>on</literal>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-lc-collate" xreflabel="lc_collate">
|
|
<term><varname>lc_collate</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>lc_collate</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Reports the locale in which sorting of textual data is done.
|
|
See <xref linkend="locale"> for more information.
|
|
The value is determined when the database cluster is initialized.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-lc-ctype" xreflabel="lc_ctype">
|
|
<term><varname>lc_ctype</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>lc_ctype</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Reports the locale that determines character classifications.
|
|
See <xref linkend="locale"> for more information.
|
|
The value is determined when the database cluster is initialized.
|
|
Ordinarily this will be the same as <varname>lc_collate</varname>,
|
|
but for special applications it might be set differently.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-max-function-args" xreflabel="max_function_args">
|
|
<term><varname>max_function_args</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>max_function_args</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Reports the maximum number of function arguments. It is determined by
|
|
the value of <literal>FUNC_MAX_ARGS</> when building the server. The
|
|
default value is 100 arguments.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-max-identifier-length" xreflabel="max_identifier_length">
|
|
<term><varname>max_identifier_length</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>max_identifier_length</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Reports the maximum identifier length. It is determined as one
|
|
less than the value of <literal>NAMEDATALEN</> when building
|
|
the server. The default value of <literal>NAMEDATALEN</> is
|
|
64; therefore the default
|
|
<varname>max_identifier_length</varname> is 63 bytes.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-max-index-keys" xreflabel="max_index_keys">
|
|
<term><varname>max_index_keys</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>max_index_keys</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Reports the maximum number of index keys. It is determined by
|
|
the value of <literal>INDEX_MAX_KEYS</> when building the server. The
|
|
default value is 32 keys.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-server-encoding" xreflabel="server_encoding">
|
|
<term><varname>server_encoding</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>server_encoding</> configuration parameter</primary>
|
|
</indexterm>
|
|
<indexterm><primary>character set</></>
|
|
<listitem>
|
|
<para>
|
|
Reports the database encoding (character set).
|
|
It is determined when the database is created. Ordinarily,
|
|
clients need only be concerned with the value of <xref
|
|
linkend="guc-client-encoding">.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-server-version" xreflabel="server_version">
|
|
<term><varname>server_version</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>server_version</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Reports the version number of the server. It is determined by the
|
|
value of <literal>PG_VERSION</> when building the server.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-server-version-num" xreflabel="server_version_num">
|
|
<term><varname>server_version_num</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>server_version_num</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Reports the version number of the server as an integer. It is determined
|
|
by the value of <literal>PG_VERSION_NUM</> when building the server.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-custom">
|
|
<title>Customized Options</title>
|
|
|
|
<para>
|
|
This feature was designed to allow parameters not normally known to
|
|
<productname>PostgreSQL</productname> to be added by add-on modules
|
|
(such as procedural languages). This allows add-on modules to be
|
|
configured in the standard ways.
|
|
</para>
|
|
|
|
<variablelist>
|
|
|
|
<varlistentry id="guc-custom-variable-classes" xreflabel="custom_variable_classes">
|
|
<term><varname>custom_variable_classes</varname> (<type>string</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>custom_variable_classes</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
This variable specifies one or several class names to be used for
|
|
custom variables, in the form of a comma-separated list. A custom
|
|
variable is a variable not normally known
|
|
to <productname>PostgreSQL</productname> proper but used by some
|
|
add-on module. Such variables must have names consisting of a class
|
|
name, a dot, and a variable name. <varname>custom_variable_classes</>
|
|
specifies all the class names in use in a particular installation.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>
|
|
The difficulty with setting custom variables in
|
|
<filename>postgresql.conf</> is that the file must be read before add-on
|
|
modules have been loaded, and so custom variables would ordinarily be
|
|
rejected as unknown. When <varname>custom_variable_classes</> is set,
|
|
the server will accept definitions of arbitrary variables within each
|
|
specified class. These variables will be treated as placeholders and
|
|
will have no function until the module that defines them is loaded. When a
|
|
module for a specific class is loaded, it will add the proper variable
|
|
definitions for its class name, convert any placeholder
|
|
values according to those definitions, and issue warnings for any
|
|
placeholders of its class that remain (which presumably would be
|
|
misspelled configuration variables).
|
|
</para>
|
|
|
|
<para>
|
|
Here is an example of what <filename>postgresql.conf</> might contain
|
|
when using custom variables:
|
|
|
|
<programlisting>
|
|
custom_variable_classes = 'plr,plperl'
|
|
plr.path = '/usr/lib/R'
|
|
plperl.use_strict = true
|
|
plruby.use_strict = true # generates error: unknown class name
|
|
</programlisting>
|
|
</para>
|
|
</sect1>
|
|
|
|
<sect1 id="runtime-config-developer">
|
|
<title>Developer Options</title>
|
|
|
|
<para>
|
|
The following parameters are intended for work on the
|
|
<productname>PostgreSQL</productname> source, and in some cases
|
|
to assist with recovery of severely damaged databases. There
|
|
should be no reason to use them in a production database setup.
|
|
As such, they have been excluded from the sample
|
|
<filename>postgresql.conf</> file. Note that many of these
|
|
parameters require special source compilation flags to work at all.
|
|
</para>
|
|
|
|
<variablelist>
|
|
<varlistentry id="guc-allow-system-table-mods" xreflabel="allow_system_table_mods">
|
|
<term><varname>allow_system_table_mods</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>allow_system_table_mods</varname> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Allows modification of the structure of system tables.
|
|
This is used by <command>initdb</command>.
|
|
This parameter can only be set at server start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-debug-assertions" xreflabel="debug_assertions">
|
|
<term><varname>debug_assertions</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>debug_assertions</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Turns on various assertion checks. This is a debugging aid. If
|
|
you are experiencing strange problems or crashes you might want
|
|
to turn this on, as it might expose programming mistakes. To use
|
|
this parameter, the macro <symbol>USE_ASSERT_CHECKING</symbol>
|
|
must be defined when <productname>PostgreSQL</productname> is
|
|
built (accomplished by the <command>configure</command> option
|
|
<option>--enable-cassert</option>). Note that
|
|
<varname>debug_assertions</varname> defaults to <literal>on</>
|
|
if <productname>PostgreSQL</productname> has been built with
|
|
assertions enabled.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-ignore-system-indexes" xreflabel="ignore_system_indexes">
|
|
<term><varname>ignore_system_indexes</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>ignore_system_indexes</varname> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Ignore system indexes when reading system tables (but still
|
|
update the indexes when modifying the tables). This is useful
|
|
when recovering from damaged system indexes.
|
|
This parameter cannot be changed after session start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-post-auth-delay" xreflabel="post_auth_delay">
|
|
<term><varname>post_auth_delay</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>post_auth_delay</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
If nonzero, a delay of this many seconds occurs when a new
|
|
server process is started, after it conducts the
|
|
authentication procedure. This is intended to give an
|
|
opportunity to attach to the server process with a debugger.
|
|
This parameter cannot be changed after session start.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-pre-auth-delay" xreflabel="pre_auth_delay">
|
|
<term><varname>pre_auth_delay</varname> (<type>integer</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>pre_auth_delay</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
If nonzero, a delay of this many seconds occurs just after a
|
|
new server process is forked, before it conducts the
|
|
authentication procedure. This is intended to give an
|
|
opportunity to attach to the server process with a debugger to
|
|
trace down misbehavior in authentication.
|
|
This parameter can only be set in the <filename>postgresql.conf</>
|
|
file or on the server command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-trace-notify" xreflabel="trace_notify">
|
|
<term><varname>trace_notify</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>trace_notify</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Generates a great amount of debugging output for the
|
|
<command>LISTEN</command> and <command>NOTIFY</command>
|
|
commands. <xref linkend="guc-client-min-messages"> or
|
|
<xref linkend="guc-log-min-messages"> must be
|
|
<literal>DEBUG1</literal> or lower to send this output to the
|
|
client or server log, respectively.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-trace-sort" xreflabel="trace_sort">
|
|
<term><varname>trace_sort</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>trace_sort</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
If on, emit information about resource usage during sort operations.
|
|
This parameter is only available if the <symbol>TRACE_SORT</symbol> macro
|
|
was defined when <productname>PostgreSQL</productname> was compiled.
|
|
(However, <symbol>TRACE_SORT</symbol> is currently defined by default.)
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>trace_locks</varname> (<type>boolean</type>)</term>
|
|
<term><varname>trace_lwlocks</varname> (<type>boolean</type>)</term>
|
|
<term><varname>trace_userlocks</varname> (<type>boolean</type>)</term>
|
|
<term><varname>trace_lock_oidmin</varname> (<type>boolean</type>)</term>
|
|
<term><varname>trace_lock_table</varname> (<type>boolean</type>)</term>
|
|
<term><varname>debug_deadlocks</varname> (<type>boolean</type>)</term>
|
|
<term><varname>log_btree_build_stats</varname> (<type>boolean</type>)</term>
|
|
<listitem>
|
|
<para>
|
|
Various other code tracing and debugging options.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-wal-debug" xreflabel="wal_debug">
|
|
<term><varname>wal_debug</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>wal_debug</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
If on, emit WAL-related debugging output. This parameter is
|
|
only available if the <symbol>WAL_DEBUG</symbol> macro was
|
|
defined when <productname>PostgreSQL</productname> was
|
|
compiled.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry id="guc-zero-damaged-pages" xreflabel="zero_damaged_pages">
|
|
<term><varname>zero_damaged_pages</varname> (<type>boolean</type>)</term>
|
|
<indexterm>
|
|
<primary><varname>zero_damaged_pages</> configuration parameter</primary>
|
|
</indexterm>
|
|
<listitem>
|
|
<para>
|
|
Detection of a damaged page header normally causes
|
|
<productname>PostgreSQL</> to report an error, aborting the current
|
|
command. Setting <varname>zero_damaged_pages</> to on causes
|
|
the system to instead report a warning, zero out the damaged page,
|
|
and continue processing. This behavior <emphasis>will destroy data</>,
|
|
namely all the rows on the damaged page. But it allows you to get
|
|
past the error and retrieve rows from any undamaged pages that might
|
|
be present in the table. So it is useful for recovering data if
|
|
corruption has occurred due to hardware or software error. You should
|
|
generally not set this on until you have given up hope of recovering
|
|
data from the damaged page(s) of a table. The
|
|
default setting is <literal>off</>, and it can only be changed
|
|
by a superuser.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect1>
|
|
<sect1 id="runtime-config-short">
|
|
<title>Short Options</title>
|
|
|
|
<para>
|
|
For convenience there are also single letter command-line option
|
|
switches available for some parameters. They are described in
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|
<xref linkend="runtime-config-short-table">. Some of these
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|
options exist for historical reasons, and their presence as a
|
|
single-letter option does not necessarily indicate an endorsement
|
|
to use the option heavily.
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</para>
|
|
|
|
<table id="runtime-config-short-table">
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|
<title>Short option key</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Short option</entry>
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|
<entry>Equivalent</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
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|
<entry><option>-A <replaceable>x</replaceable></option></entry>
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|
<entry><literal>debug_assertions = <replaceable>x</replaceable></></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-B <replaceable>x</replaceable></option></entry>
|
|
<entry><literal>shared_buffers = <replaceable>x</replaceable></></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-d <replaceable>x</replaceable></option></entry>
|
|
<entry><literal>log_min_messages = DEBUG<replaceable>x</replaceable></></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-e</option></entry>
|
|
<entry><literal>datestyle = euro</></entry>
|
|
</row>
|
|
<row>
|
|
<entry>
|
|
<option>-fb</option>, <option>-fh</option>, <option>-fi</option>,
|
|
<option>-fm</option>, <option>-fn</option>,
|
|
<option>-fs</option>, <option>-ft</option>
|
|
</entry>
|
|
<entry>
|
|
<literal>enable_bitmapscan = off</>,
|
|
<literal>enable_hashjoin = off</>,
|
|
<literal>enable_indexscan = off</>,
|
|
<literal>enable_mergejoin = off</>,
|
|
<literal>enable_nestloop = off</>,
|
|
<literal>enable_seqscan = off</>,
|
|
<literal>enable_tidscan = off</>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-F</option></entry>
|
|
<entry><literal>fsync = off</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-h <replaceable>x</replaceable></option></entry>
|
|
<entry><literal>listen_addresses = <replaceable>x</replaceable></></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-i</option></entry>
|
|
<entry><literal>listen_addresses = '*'</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-k <replaceable>x</replaceable></option></entry>
|
|
<entry><literal>unix_socket_directory = <replaceable>x</replaceable></></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-l</option></entry>
|
|
<entry><literal>ssl = on</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-N <replaceable>x</replaceable></option></entry>
|
|
<entry><literal>max_connections = <replaceable>x</replaceable></></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-O</option></entry>
|
|
<entry><literal>allow_system_table_mods = on</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-p <replaceable>x</replaceable></option></entry>
|
|
<entry><literal>port = <replaceable>x</replaceable></></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-P</option></entry>
|
|
<entry><literal>ignore_system_indexes = on</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-s</option></entry>
|
|
<entry><literal>log_statement_stats = on</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-S <replaceable>x</replaceable></option></entry>
|
|
<entry><literal>work_mem = <replaceable>x</replaceable></></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-tpa</option>, <option>-tpl</option>, <option>-te</option></entry>
|
|
<entry><literal>log_parser_stats = on</>,
|
|
<literal>log_planner_stats = on</>,
|
|
<literal>log_executor_stats = on</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><option>-W <replaceable>x</replaceable></option></entry>
|
|
<entry><literal>post_auth_delay = <replaceable>x</replaceable></></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect1>
|
|
</chapter>
|