Rename the built-in tablespaces to pg_default and pg_global, and prohibit
creation of user-defined tablespaces with names starting with 'pg_', as per suggestion of Chris K-L. Also install admin-guide tablespace documentation from Gavin.
This commit is contained in:
Tom Lane
parent
483b7f8249
commit
f5f448fb3e
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@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/diskusage.sgml,v 1.10 2003/11/29 19:51:36 pgsql Exp $
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$PostgreSQL: pgsql/doc/src/sgml/diskusage.sgml,v 1.11 2004/06/21 04:06:03 tgl Exp $
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-->
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<chapter id="diskusage">
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@ -124,20 +124,15 @@ SELECT relname, relpages FROM pg_class ORDER BY relpages DESC;
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<para>
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If you cannot free up additional space on the disk by deleting
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other things you can move some of the database files to other file
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systems and create a symlink from the original location. But
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note that <application>pg_dump</> cannot save the location layout
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information of such a setup; a restore would put everything back in
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one place. To avoid running out of disk space, you can place the
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WAL files or individual databases in other locations while creating
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them. See the <command>initdb</> documentation and <xref
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linkend="manage-ag-alternate-locs"> for more information about that.
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other things, you can move some of the database files to other file
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systems by making use of tablespaces. See <xref
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linkend="manage-ag-tablespaces"> for more information about that.
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</para>
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<tip>
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<para>
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Some file systems perform badly when they are almost full, so do
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not wait until the disk is full to take action.
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not wait until the disk is completely full to take action.
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</para>
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</tip>
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</sect1>
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@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/manage-ag.sgml,v 2.30 2004/06/18 06:13:02 tgl Exp $
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$PostgreSQL: pgsql/doc/src/sgml/manage-ag.sgml,v 2.31 2004/06/21 04:06:03 tgl Exp $
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-->
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<chapter id="managing-databases">
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@ -295,86 +295,6 @@ ALTER DATABASE mydb SET geqo TO off;
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</para>
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</sect1>
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<sect1 id="manage-ag-alternate-locs">
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<title>Alternative Locations</title>
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<para>
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XXX this is entirely dead now, and needs to be replaced by a DBA-level
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description of tablespaces.
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</para>
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<para>
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It is possible to create a database in a location other than the
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default location for the installation. But remember that all database access
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occurs through the
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database server, so any location specified must be
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accessible by the server.
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</para>
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<para>
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Alternative database locations are referenced by an environment
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variable which gives the absolute path to the intended storage
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location. This environment variable must be present in the server's
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environment, so it must have been defined before the server
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was started. (Thus, the set of available alternative locations is
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under the site administrator's control; ordinary users can't
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change it.) Any valid environment variable name may
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be used to reference an alternative location, although using
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variable names with a prefix of <literal>PGDATA</> is recommended
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to avoid confusion and conflict with other variables.
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</para>
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<para>
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To create the variable in the environment of the server process
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you must first shut down the server, define the variable,
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initialize the data area, and finally restart the server. (See also
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<xref linkend="postmaster-shutdown"> and <xref
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linkend="postmaster-start">.) To set an environment variable, type
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<programlisting>
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PGDATA2=/home/postgres/data
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export PGDATA2
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</programlisting>
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in Bourne shells, or
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<programlisting>
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setenv PGDATA2 /home/postgres/data
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</programlisting>
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in <command>csh</> or <command>tcsh</>. You have to make sure that this environment
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variable is always defined in the server environment, otherwise
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you won't be able to access that database. Therefore you probably
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want to set it in some sort of shell start-up file or server
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start-up script.
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</para>
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<para>
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<indexterm><primary>initlocation</></>
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To create a data storage area in <envar>PGDATA2</>, ensure that
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the containing directory (here, <filename>/home/postgres</filename>)
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already exists and is writable
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by the user account that runs the server (see <xref
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linkend="postgres-user">). Then from the command line, type
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<programlisting>
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initlocation PGDATA2
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</programlisting>
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(<emphasis>not</emphasis> <literal>initlocation
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$PGDATA2</literal>). Then you can restart the server.
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</para>
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<para>
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To create a database within the new location, use the command
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<synopsis>
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CREATE DATABASE <replaceable>name</> WITH LOCATION '<replaceable>location</>';
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</synopsis>
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where <replaceable>location</> is the environment variable you
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used, <envar>PGDATA2</> in this example. The <command>createdb</>
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command has the option <option>-D</> for this purpose.
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</para>
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<para>
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Databases created in alternative locations can be
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accessed and dropped like any other database.
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</para>
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</sect1>
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<sect1 id="manage-ag-dropdb">
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<title>Destroying a Database</title>
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@ -410,6 +330,116 @@ dropdb <replaceable class="parameter">dbname</replaceable>
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the database with the current user name.)
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</para>
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</sect1>
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<sect1 id="manage-ag-tablespaces">
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<title>Tablespaces</title>
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<para>
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Tablespaces in <productname>PostgreSQL</> allow database superusers to
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define locations in the file system where the files representing
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database objects can be stored. Once created, a tablespace can be referred
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to by name when creating database objects.
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</para>
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<para>
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By using tablespaces, a database administrator can control the disk
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layout of a <productname>PostgreSQL</> installation. This is useful in
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at least two ways. Firstly, if the partition or volume on which the cluster
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was initialized runs out of space and cannot be extended logically
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or otherwise, a tablespace can be created on a different partition
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and used until the system can be reconfigured.
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</para>
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<para>
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Secondly, tablespaces allow a database administrator to arrange data
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locations based on the usage patterns of database objects. For
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example, an index which is very heavily used can be placed on very fast,
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highly available disk, such as an expensive solid state device. At the same
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time a table storing archived data which is rarely used or not performance
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critical could be stored on a less expensive, slower disk system.
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</para>
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<para>
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Databases, schemas, tables, indexes and sequences can all be placed in
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particular tablespaces. To do so, a user with the <literal>CREATE</>
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privilege on a given tablespace must pass the tablespace name as a
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parameter to the relevant command. For example, the following creates
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a table in the tablespace <literal>space1</>:
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<programlisting>
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CREATE TABLE foo(i int) TABLESPACE space1;
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</programlisting>
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</para>
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<para>
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The tablespace associated with a database is used to store the system
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catalogs of that database, as well as any temporary files created by
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server processes using that database. Furthermore, it is the default
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tablespace selected for any objects created within the database, if
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no specific <literal>TABLESPACE</> clause is given when those objects
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are created. If a database is created without specifying a tablespace
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for it, it uses the same tablespace as the template database it is copied
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from.
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</para>
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<para>
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A schema does not in itself occupy any storage (other than a system
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catalog entry), so assigning a tablespace to a schema does not in itself
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do anything. What this actually does is to set a default tablespace
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for tables, indexes, and sequences later created within the schema. If
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no tablespace is mentioned when creating a schema, it inherits its
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default tablespace from the current database.
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</para>
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<para>
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The default choice of tablespace for an index is the same tablespace
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already assigned to the table the index is for.
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</para>
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<para>
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Another way to state the above rules is that when a schema, table, index
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or sequence is created without specifying a tablespace, the object
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inherits its logical parent's tablespace. A schema will be created in the
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current database's tablespace; a table or sequence will be created in the
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tablespace of the schema it is being created in; an index will be created
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in the tablespace of the table underlying the index.
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</para>
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<para>
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Two tablespaces are automatically created by <literal>initdb</>. The
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<literal>pg_global</> tablespace is used for shared system catalogs. The
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<literal>pg_default</> tablespace is the default tablespace of the
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<literal>template1</> and <literal>template0</> databases (and, therefore,
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will be the default tablespace for everything else as well, unless
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explicit <literal>TABLESPACE</> clauses are used somewhere along the
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line).
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</para>
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<para>
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Once created, a tablespace can be used from any database, provided
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the requesting user has sufficient privilege. This means that a tablespace
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cannot be dropped until all objects in all databases using the tablespace
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have been removed.
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</para>
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<para>
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To simplify the implementation of tablespaces,
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<productname>PostgreSQL</> makes extensive use of symbolic links. This
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means that tablespaces can be used <emphasis>only</> on systems
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that support symbolic links.
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</para>
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<para>
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The directory <filename>$PGDATA/pg_tblspc</> contains symbolic links that
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point to each of the non-built-in tablespaces defined in the cluster.
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Although not recommended, it is possible to adjust the tablespace
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layout by hand by redefining these links. Two warnings: do not do so
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while the postmaster is running; and after you restart the postmaster,
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update the <structname>pg_tablespace</> catalog to show the new
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locations. (If you do not, <literal>pg_dump</> will continue to show
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the old tablespace locations.)
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</para>
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</sect1>
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</chapter>
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<!-- Keep this comment at the end of the file
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@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/postmaster.sgml,v 1.49 2004/03/23 06:09:00 neilc Exp $
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$PostgreSQL: pgsql/doc/src/sgml/ref/postmaster.sgml,v 1.50 2004/06/21 04:06:04 tgl Exp $
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PostgreSQL documentation
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-->
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@ -417,18 +417,6 @@ PostgreSQL documentation
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>others</term>
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<listitem>
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<para>
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Other environment variables may be used to designate alternative
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data storage locations. See <xref linkend="manage-ag-alternate-locs"> for more
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information.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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@ -9,7 +9,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/catalog/catalog.c,v 1.53 2004/06/21 01:04:41 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/catalog/catalog.c,v 1.54 2004/06/21 04:06:05 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -119,8 +119,7 @@ GetDatabasePath(Oid dbNode, Oid spcNode)
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*
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* We now just test if the relation is in the system catalog namespace;
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* so it's no longer necessary to forbid user relations from having
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* names starting with pg_. Now only schema names have the pg_
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* distinction/requirement.
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* names starting with pg_.
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*/
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bool
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IsSystemRelation(Relation relation)
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@ -200,8 +199,8 @@ IsToastNamespace(Oid namespaceId)
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* True iff name starts with the pg_ prefix.
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*
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* For some classes of objects, the prefix pg_ is reserved for
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* system objects only. As of 7.3, this is now only true for
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* schema names.
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* system objects only. As of 7.5, this is only true for
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* schema and tablespace names.
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*/
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bool
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IsReservedName(const char *name)
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@ -19,8 +19,8 @@
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* Thus the full path to an arbitrary file is
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* $PGDATA/pg_tblspc/spcoid/dboid/relfilenode
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*
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* There are two tablespaces created at initdb time: global (for shared
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* tables) and default (for everything else). For backwards compatibility
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* There are two tablespaces created at initdb time: pg_global (for shared
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* tables) and pg_default (for everything else). For backwards compatibility
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* and to remain functional on platforms without symlinks, these tablespaces
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* are accessed specially: they are respectively
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* $PGDATA/global/relfilenode
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@ -45,7 +45,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/tablespace.c,v 1.2 2004/06/21 01:04:42 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/commands/tablespace.c,v 1.3 2004/06/21 04:06:06 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -233,6 +233,17 @@ CreateTableSpace(CreateTableSpaceStmt *stmt)
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errmsg("tablespace location \"%s\" is too long",
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location)));
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/*
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* Disallow creation of tablespaces named "pg_xxx"; we reserve this
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* namespace for system purposes.
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*/
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if (!allowSystemTableMods && IsReservedName(stmt->tablespacename))
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ereport(ERROR,
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(errcode(ERRCODE_RESERVED_NAME),
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errmsg("unacceptable tablespace name \"%s\"",
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stmt->tablespacename),
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errdetail("The prefix \"pg_\" is reserved for system tablespaces.")));
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/*
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* Check that there is no other tablespace by this name. (The
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* unique index would catch this anyway, but might as well give
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@ -37,7 +37,7 @@
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* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.238 2004/06/21 01:04:45 momjian Exp $
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* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.239 2004/06/21 04:06:07 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -53,6 +53,6 @@
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*/
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/* yyyymmddN */
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#define CATALOG_VERSION_NO 200406201
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#define CATALOG_VERSION_NO 200406202
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#endif
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@ -8,7 +8,7 @@
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* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/catalog/pg_tablespace.h,v 1.1 2004/06/18 06:14:06 tgl Exp $
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* $PostgreSQL: pgsql/src/include/catalog/pg_tablespace.h,v 1.2 2004/06/21 04:06:07 tgl Exp $
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*
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* NOTES
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* the genbki.sh script reads this file and generates .bki
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@ -57,8 +57,8 @@ typedef FormData_pg_tablespace *Form_pg_tablespace;
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#define Anum_pg_tablespace_spclocation 3
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#define Anum_pg_tablespace_spcacl 4
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DATA(insert OID = 1663 ( default PGUID "" _null_ ));
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DATA(insert OID = 1664 ( global PGUID "" _null_ ));
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DATA(insert OID = 1663 ( pg_default PGUID "" _null_ ));
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DATA(insert OID = 1664 ( pg_global PGUID "" _null_ ));
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#define DEFAULTTABLESPACE_OID 1663
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#define GLOBALTABLESPACE_OID 1664
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Loading…
Reference in New Issue