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Merge documentation updates from 7.3 branch.

This commit is contained in:
Peter Eisentraut 2002-11-11 20:14:04 +00:00
parent b327906683
commit 1b342df00a
28 changed files with 2330 additions and 2479 deletions
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46
doc/src/sgml/advanced.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/advanced.sgml,v 1.30 2002/10/24 17:48:54 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/advanced.sgml,v 1.31 2002/11/11 20:14:02 petere Exp $
-->
<chapter id="tutorial-advanced">
@ -46,14 +46,14 @@ $Header: /cvsroot/pgsql/doc/src/sgml/advanced.sgml,v 1.30 2002/10/24 17:48:54 pe
<firstterm>view</firstterm> over the query, which gives a name to
the query that you can refer to like an ordinary table.
<programlisting>
<programlisting>
CREATE VIEW myview AS
SELECT city, temp_lo, temp_hi, prcp, date, location
FROM weather, cities
WHERE city = name;
SELECT * FROM myview;
</programlisting>
</programlisting>
</para>
<para>
@ -101,7 +101,7 @@ SELECT * FROM myview;
<para>
The new declaration of the tables would look like this:
<programlisting>
<programlisting>
CREATE TABLE cities (
city varchar(80) primary key,
location point
@ -114,23 +114,23 @@ CREATE TABLE weather (
prcp real,
date date
);
</programlisting>
</programlisting>
Now try inserting an invalid record:
<programlisting>
<programlisting>
INSERT INTO weather VALUES ('Berkeley', 45, 53, 0.0, '1994-11-28');
</programlisting>
</programlisting>
<screen>
<screen>
ERROR: &lt;unnamed&gt; referential integrity violation - key referenced from weather not found in cities
</screen>
</screen>
</para>
<para>
The behavior of foreign keys can be finely tuned to your
application. We will not go beyond this simple example in this
tutorial, but just refer you to the &cite-reference;
tutorial, but just refer you to the &cite-user;
for more information. Making correct use of
foreign keys will definitely improve the quality of your database
applications, so you are strongly encouraged to learn about them.
@ -161,7 +161,7 @@ ERROR: &lt;unnamed&gt; referential integrity violation - key referenced from we
to Bob's account. Simplifying outrageously, the SQL commands for this
might look like
<programlisting>
<programlisting>
UPDATE accounts SET balance = balance - 100.00
WHERE name = 'Alice';
UPDATE branches SET balance = balance - 100.00
@ -170,7 +170,7 @@ UPDATE accounts SET balance = balance + 100.00
WHERE name = 'Bob';
UPDATE branches SET balance = balance + 100.00
WHERE name = (SELECT branch_name FROM accounts WHERE name = 'Bob');
</programlisting>
</programlisting>
</para>
<para>
@ -222,13 +222,13 @@ UPDATE branches SET balance = balance + 100.00
<command>BEGIN</> and <command>COMMIT</> commands. So our banking
transaction would actually look like
<programlisting>
<programlisting>
BEGIN;
UPDATE accounts SET balance = balance - 100.00
WHERE name = 'Alice';
-- etc etc
COMMIT;
</programlisting>
</programlisting>
</para>
<para>
@ -278,7 +278,7 @@ COMMIT;
implicitly when you list all cities. If you're really clever you
might invent some scheme like this:
<programlisting>
<programlisting>
CREATE TABLE capitals (
name text,
population real,
@ -296,7 +296,7 @@ CREATE VIEW cities AS
SELECT name, population, altitude FROM capitals
UNION
SELECT name, population, altitude FROM non_capitals;
</programlisting>
</programlisting>
This works OK as far as querying goes, but it gets ugly when you
need to update several rows, to name one thing.
@ -305,7 +305,7 @@ CREATE VIEW cities AS
<para>
A better solution is this:
<programlisting>
<programlisting>
CREATE TABLE cities (
name text,
population real,
@ -315,7 +315,7 @@ CREATE TABLE cities (
CREATE TABLE capitals (
state char(2)
) INHERITS (cities);
</programlisting>
</programlisting>
</para>
<para>
@ -336,11 +336,11 @@ CREATE TABLE capitals (
including state capitals, that are located at an altitude
over 500 ft.:
<programlisting>
<programlisting>
SELECT name, altitude
FROM cities
WHERE altitude &gt; 500;
</programlisting>
</programlisting>
which returns:
@ -359,11 +359,11 @@ SELECT name, altitude
all the cities that are not state capitals and
are situated at an altitude of 500 ft. or higher:
<programlisting>
<programlisting>
SELECT name, altitude
FROM ONLY cities
WHERE altitude &gt; 500;
</programlisting>
</programlisting>
<screen>
name | altitude
@ -380,7 +380,7 @@ SELECT name, altitude
<classname>cities</classname> table, and not tables below
<classname>cities</classname> in the inheritance hierarchy. Many
of the commands that we have already discussed --
<command>SELECT</command>, <command>UPDATE</command> and
<command>SELECT</command>, <command>UPDATE</command>, and
<command>DELETE</command> -- support this <literal>ONLY</literal>
notation.
</para>

24
doc/src/sgml/array.sgml
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@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/array.sgml,v 1.23 2002/11/10 00:32:16 momjian Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/array.sgml,v 1.24 2002/11/11 20:14:02 petere Exp $ -->
<sect1 id="arrays">
<title>Arrays</title>
@ -21,7 +21,7 @@ CREATE TABLE sal_emp (
</programlisting>
As shown, an array data type is named by appending square brackets
(<literal>[]</>) to the data type name of the array elements.
The above query will create a table named
The above command will create a table named
<structname>sal_emp</structname> with columns including
a <type>text</type> string (<structfield>name</structfield>),
a one-dimensional array of type
@ -68,7 +68,7 @@ SELECT name FROM sal_emp WHERE pay_by_quarter[1] &lt;&gt; pay_by_quarter[2];
The array subscript numbers are written within square brackets.
By default <productname>PostgreSQL</productname> uses the
<quote>one-based</quote> numbering convention for arrays, that is,
one-based numbering convention for arrays, that is,
an array of <replaceable>n</> elements starts with <literal>array[1]</literal> and
ends with <literal>array[<replaceable>n</>]</literal>.
</para>
@ -90,10 +90,9 @@ SELECT pay_by_quarter[3] FROM sal_emp;
<para>
We can also access arbitrary rectangular slices of an array, or
subarrays. An array slice is denoted by writing
<literal><replaceable>lower subscript</replaceable> :
<replaceable>upper subscript</replaceable></literal> for one or more
array dimensions. This query retrieves the first item on Bill's
schedule for the first two days of the week:
<literal><replaceable>lower-bound</replaceable>:<replaceable>upper-bound</replaceable></literal>
for one or more array dimensions. This query retrieves the first
item on Bill's schedule for the first two days of the week:
<programlisting>
SELECT schedule[1:2][1:1] FROM sal_emp WHERE name = 'Bill';
@ -112,9 +111,10 @@ SELECT schedule[1:2][1] FROM sal_emp WHERE name = 'Bill';
with the same result. An array subscripting operation is taken to
represent an array slice if any of the subscripts are written in the
form <replaceable>lower</replaceable> <literal>:</literal>
<replaceable>upper</replaceable>. A lower bound of 1 is assumed for
any subscript where only one value is specified.
form
<literal><replaceable>lower</replaceable>:<replaceable>upper</replaceable></literal>.
A lower bound of 1 is assumed for any subscript where only one value
is specified.
</para>
<para>
@ -310,7 +310,7 @@ SELECT * FROM sal_emp WHERE pay_by_quarter **= 10000;
<tip>
<para>
Remember that what you write in an SQL query will first be interpreted
Remember that what you write in an SQL command will first be interpreted
as a string literal, and then as an array. This doubles the number of
backslashes you need. For example, to insert a <type>text</> array
value containing a backslash and a double quote, you'd need to write
@ -323,7 +323,7 @@ INSERT ... VALUES ('{"\\\\","\\""}');
become <literal>\</> and <literal>"</> respectively. (If we were working
with a data type whose input routine also treated backslashes specially,
<type>bytea</> for example, we might need as many as eight backslashes
in the query to get one backslash into the stored array element.)
in the command to get one backslash into the stored array element.)
</para>
</tip>

51
doc/src/sgml/backup.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/backup.sgml,v 2.23 2002/10/21 02:11:37 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/backup.sgml,v 2.24 2002/11/11 20:14:02 petere Exp $
-->
<chapter id="backup">
<title>Backup and Restore</title>
@ -64,7 +64,7 @@ pg_dump <replaceable class="parameter">dbname</replaceable> &gt; <replaceable cl
<para>
As any other <productname>PostgreSQL</> client application,
<application>pg_dump</> will by default connect with the database
user name that is equal to the current Unix user name. To override
user name that is equal to the current operating system user name. To override
this, either specify the <option>-U</option> option or set the
environment variable <envar>PGUSER</envar>. Remember that
<application>pg_dump</> connections are subject to the normal
@ -104,9 +104,9 @@ psql <replaceable class="parameter">dbname</replaceable> &lt; <replaceable class
</synopsis>
where <replaceable class="parameter">infile</replaceable> is what
you used as <replaceable class="parameter">outfile</replaceable>
for the pg_dump command. The database <replaceable
for the <command>pg_dump</> command. The database <replaceable
class="parameter">dbname</replaceable> will not be created by this
command, you must create it yourself from template0 before executing
command, you must create it yourself from <literal>template0</> before executing
<application>psql</> (e.g., with <literal>createdb -T template0
<replaceable class="parameter">dbname</></literal>).
<application>psql</> supports similar options to <application>pg_dump</>
@ -129,23 +129,22 @@ psql <replaceable class="parameter">dbname</replaceable> &lt; <replaceable class
The ability of <application>pg_dump</> and <application>psql</> to
write to or read from pipes makes it possible to dump a database
directly from one server to another, for example
<informalexample>
<programlisting>
pg_dump -h <replaceable>host1</> <replaceable>dbname</> | psql -h <replaceable>host2</> <replaceable>dbname</>
</programlisting>
</informalexample>
</para>
<important>
<para>
The dumps produced by pg_dump are relative to template0. This means
that any languages, procedures, etc. added to template1 will also be
dumped by <application>pg_dump</>. As a result, when restoring, if
you are using a customized template1, you must create the empty
database from template0, as in the example above.
</para>
</important>
<important>
<para>
The dumps produced by <application>pg_dump</> are relative to
<literal>template0</>. This means that any languages, procedures,
etc. added to <literal>template1</> will also be dumped by
<application>pg_dump</>. As a result, when restoring, if you are
using a customized <literal>template1</>, you must create the
empty database from <literal>template0</>, as in the example
above.
</para>
</important>
</sect2>
@ -222,20 +221,16 @@ cat <replaceable class="parameter">filename</replaceable>.gz | gunzip | psql <re
acceptable in size to the underlying file system. For example, to
make chunks of 1 megabyte:
<informalexample>
<programlisting>
pg_dump <replaceable class="parameter">dbname</replaceable> | split -b 1m - <replaceable class="parameter">filename</replaceable>
</programlisting>
</informalexample>
Reload with
<informalexample>
<programlisting>
createdb <replaceable class="parameter">dbname</replaceable>
cat <replaceable class="parameter">filename</replaceable>* | psql <replaceable class="parameter">dbname</replaceable>
</programlisting>
</informalexample>
</para>
</formalpara>
@ -249,14 +244,11 @@ cat <replaceable class="parameter">filename</replaceable>* | psql <replaceable c
restored selectively. The following command dumps a database using the
custom dump format:
<informalexample>
<programlisting>
pg_dump -Fc <replaceable class="parameter">dbname</replaceable> > <replaceable class="parameter">filename</replaceable>
</programlisting>
</informalexample>
See the <application>pg_dump</> and <application>pg_restore</> reference pages for details.
</para>
</formalpara>
@ -284,7 +276,7 @@ pg_dump -Fc <replaceable class="parameter">dbname</replaceable> > <replaceable c
<para>
For reasons of backward compatibility, <application>pg_dump</> does
not dump large objects by default. To dump large objects you must use
either the custom or the TAR output format, and use the -b option in
either the custom or the TAR output format, and use the <option>-b</> option in
<application>pg_dump</>. See the reference pages for details.
The directory <filename>contrib/pg_dumplo</> of the
<productname>PostgreSQL</> source tree also contains a program that can
@ -308,11 +300,10 @@ pg_dump -Fc <replaceable class="parameter">dbname</replaceable> > <replaceable c
are located, but you have probably found them already if you are
interested in this method. You can use whatever method you prefer
for doing usual file system backups, for example
<informalexample>
<programlisting>
tar -cf backup.tar /usr/local/pgsql/data
</programlisting>
</informalexample>
</para>
<para>
@ -390,11 +381,11 @@ tar -cf backup.tar /usr/local/pgsql/data
The least downtime can be achieved by installing the new server in
a different directory and running both the old and the new servers
in parallel, on different ports. Then you can use something like
<informalexample>
<programlisting>
pg_dumpall -p 5432 | psql -d template1 -p 6543
</programlisting>
</informalexample>
to transfer your data, or use an intermediate file if you want.
Then you can shut down the old server and start the new server at
the port the old one was running at. You should make sure that the
@ -410,7 +401,7 @@ pg_dumpall -p 5432 | psql -d template1 -p 6543
do the back up step before installing the new version, bring down
the server, move the old version out of the way, install the new
version, start the new server, restore the data. For example:
<informalexample>
<programlisting>
pg_dumpall > backup
pg_ctl stop
@ -421,7 +412,7 @@ initdb -D /usr/local/pgsql/data
postmaster -D /usr/local/pgsql/data
psql template1 < backup
</programlisting>
</informalexample>
See <xref linkend="runtime"> about ways to start and stop the
server and other details. The installation instructions will advise
you of strategic places to perform these steps.

29
doc/src/sgml/client-auth.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/client-auth.sgml,v 1.39 2002/09/21 18:32:52 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/client-auth.sgml,v 1.40 2002/11/11 20:14:02 petere Exp $
-->
<chapter id="client-authentication">
@ -62,7 +62,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/client-auth.sgml,v 1.39 2002/09/21 18:32:52
</para>
<para>
The general format of the <filename>pg_hba.conf</filename> file is of
The general format of the <filename>pg_hba.conf</filename> file is
a set of records, one per line. Blank lines are ignored, as is any
text after the <quote>#</quote> comment character. A record is made
up of a number of fields which are separated by spaces and/or tabs.
@ -305,8 +305,9 @@ hostssl <replaceable>database</replaceable> <replaceable>user</replaceable> <
<para>
If you use the map <literal>sameuser</literal>, the user
names are assumed to be identical. If not, the map name is
looked up in the <literal>$PGDATA/pg_ident.conf</literal>
file. The connection is accepted if that file contains an
looked up in the file <filename>pg_ident.conf</filename>
in the same directory as <filename>pg_hba.conf</filename>.
The connection is accepted if that file contains an
entry for this map name with the ident-supplied user name
and the requested <productname>PostgreSQL</productname> user
name.
@ -473,7 +474,7 @@ local db1,db2,@demodbs all md5
<para>
When <literal>trust</> authentication is specified,
<productname>PostgreSQL</productname> assumes that anyone who can
connect to the postmaster is authorized to access the database as
connect to the server is authorized to access the database as
whatever database user he specifies (including the database superuser).
This method should only be used when there is adequate system-level
protection on connections to the postmaster port.
@ -504,7 +505,7 @@ local db1,db2,@demodbs all md5
<para>
<literal>trust</> authentication is only suitable for TCP connections
if you trust every user on every machine that is allowed to connect
to the postmaster by the <filename>pg_hba.conf</> lines that specify
to the server by the <filename>pg_hba.conf</> lines that specify
<literal>trust</>. It is seldom reasonable to use <literal>trust</>
for any TCP connections other than those from <systemitem>localhost</> (127.0.0.1).
</para>
@ -538,14 +539,14 @@ local db1,db2,@demodbs all md5
<para>
<productname>PostgreSQL</productname> database passwords are
separate from operating system user passwords. Ordinarily, the
password for each database user is stored in the pg_shadow system
separate from operating system user passwords. The password for
each database user is stored in the <literal>pg_shadow</> system
catalog table. Passwords can be managed with the query language
commands <command>CREATE USER</command> and <command>ALTER
USER</command>, e.g., <userinput>CREATE USER foo WITH PASSWORD
'secret';</userinput>. By default, that is, if no password has been
set up, the stored password is <literal>NULL</literal> and password
authentication will always fail for that user.
'secret';</userinput>. By default, that is, if no password has
been set up, the stored password is null and
password authentication will always fail for that user.
</para>
<para>
@ -554,8 +555,8 @@ local db1,db2,@demodbs all md5
file. The file should contain user names separated by commas or one
user name per line, and be in the same directory as
<filename>pg_hba.conf</>. Mention the (base) name of the file
preceded with <literal>@</>in the <literal>USER</> column. The
<literal>DATABASE</> column can similarly accept a list of values or
preceded with <literal>@</> in the user column. The
database column can similarly accept a list of values or
a file name. You can also specify group names by preceding the group
name with <literal>+</>.
</para>
@ -715,7 +716,7 @@ local db1,db2,@demodbs all md5
Unix-domain sockets (currently <systemitem
class="osname">Linux</>, <systemitem class="osname">FreeBSD</>,
<systemitem class="osname">NetBSD</>, and <systemitem
class="osname">BSD/OS</>, ident authentication can also be applied
class="osname">BSD/OS</>), ident authentication can also be applied
to local connections. In this case, no security risk is added by
using ident authentication; indeed it is a preferable choice for
local connections on such systems.

795
doc/src/sgml/datatype.sgml
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552
doc/src/sgml/datetime.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/datetime.sgml,v 2.28 2002/08/04 06:15:45 thomas Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/datetime.sgml,v 2.29 2002/11/11 20:14:02 petere Exp $
Date/time details
-->
@ -8,7 +8,7 @@ Date/time details
<para>
<productname>PostgreSQL</productname> uses an internal heuristic
parser for all date/time support. Dates and times are input as
parser for all date/time input support. Dates and times are input as
strings, and are broken up into distinct fields with a preliminary
determination of what kind of information may be in the
field. Each field is interpreted and either assigned a numeric
@ -25,10 +25,203 @@ Date/time details
</para>
<sect1>
<title>Date/Time Keywords</title>
<title>Date/Time Input Interpretation</title>
<para>
<table tocentry="1">
The date/time types are all decoded using a common set of routines.
</para>
<procedure>
<title>Date/Time Input Interpretation</title>
<step>
<para>
Break the input string into tokens and categorize each token as
a string, time, time zone, or number.
</para>
<substeps>
<step>
<para>
If the numeric token contains a colon (<literal>:</>), this is
a time string. Include all subsequent digits and colons.
</para>
</step>
<step>
<para>
If the numeric token contains a dash (<literal>-</>), slash
(<literal>/</>), or two or more dots (<literal>.</>), this is
a date string which may have a text month.
</para>
</step>
<step>
<para>
If the token is numeric only, then it is either a single field
or an ISO 8601 concatenated date (e.g.,
<literal>19990113</literal> for January 13, 1999) or time
(e.g. <literal>141516</literal> for 14:15:16).
</para>
</step>
<step>
<para>
If the token starts with a plus (<literal>+</>) or minus
(<literal>-</>), then it is either a time zone or a special
field.
</para>
</step>
</substeps>
</step>
<step>
<para>
If the token is a text string, match up with possible strings.
</para>
<substeps>
<step>
<para>
Do a binary-search table lookup for the token
as either a special string (e.g., <literal>today</literal>),
day (e.g., <literal>Thursday</literal>),
month (e.g., <literal>January</literal>),
or noise word (e.g., <literal>at</literal>, <literal>on</literal>).
</para>
<para>
Set field values and bit mask for fields.
For example, set year, month, day for <literal>today</literal>,
and additionally hour, minute, second for <literal>now</literal>.
</para>
</step>
<step>
<para>
If not found, do a similar binary-search table lookup to match
the token with a time zone.
</para>
</step>
<step>
<para>
If not found, throw an error.
</para>
</step>
</substeps>
</step>
<step>
<para>
The token is a number or number field.
</para>
<substeps>
<step>
<para>
If there are more than 4 digits,
and if no other date fields have been previously read, then interpret
as a <quote>concatenated date</quote> (e.g., <literal>19990118</literal>). 8
and 6 digits are interpreted as year, month, and day, while 7
and 5 digits are interpreted as year, day of year, respectively.
</para>
</step>
<step>
<para>
If the token is three digits
and a year has already been decoded, then interpret as day of year.
</para>
</step>
<step>
<para>
If four or six digits and a year has already been read, then
interpret as a time.
</para>
</step>
<step>
<para>
If four or more digits, then interpret as a year.
</para>
</step>
<step>
<para>
If in European date mode, and if the day field has not yet been read,
and if the value is less than or equal to 31, then interpret as a day.
</para>
</step>
<step>
<para>
If the month field has not yet been read,
and if the value is less than or equal to 12, then interpret as a month.
</para>
</step>
<step>
<para>
If the day field has not yet been read,
and if the value is less than or equal to 31, then interpret as a day.
</para>
</step>
<step>
<para>
If two digits or four or more digits, then interpret as a year.
</para>
</step>
<step>
<para>
Otherwise, throw an error.
</para>
</step>
</substeps>
</step>
<step>
<para>
If BC has been specified, negate the year and add one for
internal storage. (There is no year zero in the Gregorian
calendar, so numerically <literal>1BC</literal> becomes year
zero.)
</para>
</step>
<step>
<para>
If BC was not specified, and if the year field was two digits in length, then
adjust the year to 4 digits. If the field was less than 70, then add 2000;
otherwise, add 1900.
<tip>
<para>
Gregorian years AD 1-99 may be entered by using 4 digits with leading
zeros (e.g., <literal>0099</> is AD 99). Previous versions of
<productname>PostgreSQL</productname> accepted years with three
digits and with single digits, but as of version 7.0 the rules have
been tightened up to reduce the possibility of ambiguity.
</para>
</tip>
</para>
</step>
</procedure>
</sect1>
<sect1>
<title>Date/Time Key Words</title>
<para>
<xref linkend="datetime-month-table"> shows the tokens that are
permissible as abbreviations for the names of the month.
</para>
<table id="datetime-month-table">
<title>Month Abbreviations</title>
<tgroup cols="2">
<thead>
@ -88,13 +281,17 @@ Date/time details
<note>
<para>
The month <literal>May</literal> has no explicit abbreviation, for obvious reasons.
The month May has no explicit abbreviation, for obvious reasons.
</para>
</note>
</para>
<para>
<table tocentry="1">
<xref linkend="datetime-dow-table"> shows the tokens that are
permissible as abbreviations for the names of the days of the
week.
</para>
<table id="datetime-dow-table">
<title>Day of the Week Abbreviations</title>
<tgroup cols="2">
<thead>
@ -135,12 +332,14 @@ Date/time details
</tbody>
</tgroup>
</table>
</para>
<para>
<table tocentry="1">
<title><productname>PostgreSQL</productname> Field Modifiers</title>
<titleabbrev>Field Modifiers</titleabbrev>
<xref linkend="datetime-mod-table"> shows the tokens that serve
various modifier purposes.
</para>
<table id="datetime-mod-table">
<title>Date/Time Field Modifiers</title>
<tgroup cols="2">
<thead>
<row>
@ -151,7 +350,7 @@ Date/time details
<tbody>
<row>
<entry><literal>ABSTIME</literal></entry>
<entry>Keyword ignored</entry>
<entry>Key word ignored</entry>
</row>
<row>
<entry><literal>AM</literal></entry>
@ -159,7 +358,7 @@ Date/time details
</row>
<row>
<entry><literal>AT</literal></entry>
<entry>Keyword ignored</entry>
<entry>Key word ignored</entry>
</row>
<row>
<entry><literal>JULIAN</>, <literal>JD</>, <literal>J</></entry>
@ -167,7 +366,7 @@ Date/time details
</row>
<row>
<entry><literal>ON</literal></entry>
<entry>Keyword ignored</entry>
<entry>Key word ignored</entry>
</row>
<row>
<entry><literal>PM</literal></entry>
@ -180,44 +379,40 @@ Date/time details
</tbody>
</tgroup>
</table>
</para>
<para>
The keyword <literal>ABSTIME</literal> is ignored for historical
The key word <literal>ABSTIME</literal> is ignored for historical
reasons; in very old releases of
<productname>PostgreSQL</productname> invalid <type>ABSTIME</type>
fields were emitted as <literal>Invalid Abstime</literal>. This is no
longer the case however and this keyword will likely be dropped in
<productname>PostgreSQL</productname> invalid fields of type <type>abstime</type>
were emitted as <literal>Invalid Abstime</literal>. This is no
longer the case however and this key word will likely be dropped in
a future release.
</para>
</sect1>
<sect1 id="timezones">
<title>Time Zones</title>
<indexterm zone="timezones">
<indexterm>
<primary>time zones</primary>
</indexterm>
<para>
<xref linkend="datetime-timezone-table"> shows the time zone
abbreviations recognized by <productname>PostgreSQL</productname>.
<productname>PostgreSQL</productname> contains internal tabular
information for time zone decoding, since there is no *nix standard
system interface to provide access to general, cross-timezone
information. The underlying OS <emphasis>is</emphasis> used to
provide time zone information for <emphasis>output</emphasis>, however.
information for time zone decoding, since there is no standard
operating system interface to provide access to general,
cross-time zone information. The underlying operating system
<emphasis>is</emphasis> used to provide time zone information for
<emphasis>output</emphasis>, however.
</para>
<para>
The following table of time zones recognized by
<productname>PostgreSQL</productname> is organized by time
zone offset from UTC, rather than alphabetically; this is intended
to facilitate
The table is organized by time zone offset from <acronym>UTC</>,
rather than alphabetically; this is intended to facilitate
matching local usage with recognized abbreviations for cases where
these might differ.
</para>
<table tocentry="1">
<title><productname>PostgreSQL</productname> Recognized Time Zones</title>
<titleabbrev>Time Zones</titleabbrev>
<table id="datetime-timezone-table">
<title>Time Zone Abbreviations</title>
<tgroup cols="3">
<thead>
<row>
@ -749,31 +944,29 @@ Date/time details
</tbody>
</tgroup>
</table>
</para>
<sect2>
<formalpara>
<title>Australian Time Zones</title>
<para>
Australian time zones and their naming variants
account for fully one quarter of all time zones in the
<productname>PostgreSQL</productname> time zone lookup table.
There are two naming conflicts with time zones commonly used
in the United States, <literal>CST</literal> and <literal>EST</literal>.
There are three naming conflicts between Australian time zone
names with time zones commonly used in North and South America:
<literal>ACST</literal>, <literal>CST</literal>, and
<literal>EST</literal>. If the run-time option
<varname>AUSTRALIAN_TIMEZONES</varname> is set to true then
<literal>ACST</literal>, <literal>CST</literal>,
<literal>EST</literal>, and <literal>SAT</literal> are interpreted
as Australian time zone names, as shown in <xref
linkend="datetime-oztz-table">. If it is false (which is the
default), then <literal>ACST</literal>, <literal>CST</literal>,
and <literal>EST</literal> are taken as American time zone names,
and <literal>SAT</literal> is interpreted as a noise word
indicating Saturday.
</para>
</formalpara>
<para>
If the run-time option <literal>AUSTRALIAN_TIMEZONES</literal> is set
then <literal>CST</literal>, <literal>EST</literal>, and
<literal>SAT</literal> will be
interpreted as Australian timezone names. Without this option,
<literal>CST</literal> and <literal>EST</literal> are taken as
American timezone names, while <literal>SAT</literal> is interpreted as a
noise word indicating <literal>Saturday</literal>.
<table tocentry="1">
<title><productname>PostgreSQL</productname> Australian Time Zones</title>
<titleabbrev>Australian Time Zones</titleabbrev>
<table id="datetime-oztz-table">
<title>Australian Time Zone Abbreviations</title>
<tgroup cols="3">
<thead>
<row>
@ -806,196 +999,10 @@ Date/time details
</tbody>
</tgroup>
</table>
</para>
</sect2>
<sect2>
<title>Date/Time Input Interpretation</title>
</sect1>
<para>
The date/time types are all decoded using a common set of routines.
</para>
<procedure>
<title>Date/Time Input Interpretation</title>
<step>
<para>
Break the input string into tokens and categorize each token as
a string, time, time zone, or number.
</para>
<substeps>
<step>
<para>
If the numeric token contains a colon (":"), this is a time
string. Include all subsequent digits and colons.
</para>
</step>
<step>
<para>
If the numeric token contains a dash ("-"), slash ("/"), or
two or more dots ("."),
this is a date string which may have a text month.
</para>
</step>
<step>
<para>
If the token is numeric only, then it is either a single field
or an ISO-8601 concatenated date
(e.g. <literal>19990113</literal> for January 13, 1999)
or time (e.g. 141516 for 14:15:16).
</para>
</step>
<step>
<para>
If the token starts with a plus ("+") or minus ("-"),
then it is either a time zone or a special field.
</para>
</step>
</substeps>
</step>
<step>
<para>
If the token is a text string, match up with possible strings.
</para>
<substeps>
<step>
<para>
Do a binary-search table lookup for the token
as either a special string (e.g. <literal>today</literal>),
day (e.g. <literal>Thursday</literal>),
month (e.g. <literal>January</literal>),
or noise word (e.g. <literal>at</literal>, <literal>on</literal>).
</para>
<para>
Set field values and bit mask for fields.
For example, set year, month, day for <literal>today</literal>,
and additionally hour, minute, second for <literal>now</literal>.
</para>
</step>
<step>
<para>
If not found, do a similar binary-search table lookup to match
the token with a time zone.
</para>
</step>
<step>
<para>
If not found, throw an error.
</para>
</step>
</substeps>
</step>
<step>
<para>
The token is a number or number field.
</para>
<substeps>
<step>
<para>
If there are more than 4 digits,
and if no other date fields have been previously read, then interpret
as a <quote>concatenated date</quote> (e.g. <literal>19990118</literal>). 8
and 6 digits are interpreted as year, month, and day, while 7
and 5 digits are interpreted as year, day of year, respectively.
</para>
</step>
<step>
<para>
If the token is three digits
and a year has already been decoded, then interpret as day of year.
</para>
</step>
<step>
<para>
If four or six digits and a year has already been read, then
interpret as a time.
</para>
</step>
<step>
<para>
If four or more digits, then interpret as a year.
</para>
</step>
<step>
<para>
If in European date mode, and if the day field has not yet been read,
and if the value is less than or equal to 31, then interpret as a day.
</para>
</step>
<step>
<para>
If the month field has not yet been read,
and if the value is less than or equal to 12, then interpret as a month.
</para>
</step>
<step>
<para>
If the day field has not yet been read,
and if the value is less than or equal to 31, then interpret as a day.
</para>
</step>
<step>
<para>
If two digits or four or more digits, then interpret as a year.
</para>
</step>
<step>
<para>
Otherwise, throw an error.
</para>
</step>
</substeps>
</step>
<step>
<para>
If BC has been specified, negate the year and add one for
internal storage
(there is no year zero in the Gregorian calendar, so numerically
<literal>1BC</literal> becomes year zero).
</para>
</step>
<step>
<para>
If BC was not specified, and if the year field was two digits in length, then
adjust the year to 4 digits. If the field was less than 70, then add 2000;
otherwise, add 1900.
<tip>
<para>
Gregorian years 1-99AD may be entered by using 4 digits with leading
zeros (e.g. 0099 is 99AD). Previous versions of
<productname>PostgreSQL</productname> accepted years with three
digits and with single digits, but as of version 7.0 the rules have
been tightened up to reduce the possibility of ambiguity.
</para>
</tip>
</para>
</step>
</procedure>
</sect2>
</sect1>
<sect1 id="units-history">
<sect1 id="units-history">
<title>History of Units</title>
<note>
@ -1015,22 +1022,20 @@ Date/time details
to noon UTC on 2 January 4713 BC.
</para>
<para>
<quote>Julian Day</quote> is different from <quote>Julian Date</quote>.
The Julian calendar was introduced by Julius Caesar in 45 BC. It was
in common use until the 1582, when countries started changing to the
Gregorian calendar.
In the Julian calendar, the tropical year is approximated as 365 1/4
days = 365.25 days. This gives an error of about 1 day in
128 years.
The accumulating calendar error prompted Pope Gregory XIII
to reform the calendar in accordance with instructions
from the Council of Trent.
<para>
The <quote>Julian Day</quote> is different from the <quote>Julian
Date</quote>. The Julian date refers to the Julian calendar, which
was introduced by Julius Caesar in 45 BC. It was in common use
until the 1582, when countries started changing to the Gregorian
calendar. In the Julian calendar, the tropical year is
approximated as 365 1/4 days = 365.25 days. This gives an error of
about 1 day in 128 years.
</para>
<para>
The accumulating calendar error prompted
Pope Gregory XIII to reform the calendar in accordance with
instructions from the Council of Trent.
In the Gregorian calendar, the tropical year is approximated as
365 + 97 / 400 days = 365.2425 days. Thus it takes approximately 3300
years for the tropical year to shift one day with respect to the
@ -1066,37 +1071,36 @@ Date/time details
This was observed in Italy, Poland, Portugal, and Spain. Other Catholic
countries followed shortly after, but Protestant countries were
reluctant to change, and the Greek orthodox countries didn't change
until the start of this century.
until the start of the 20th century.
The reform was observed by Great Britain and Dominions (including what is
now the USA) in 1752.
Thus 2 Sep 1752 was followed by 14 Sep 1752.
Thus 2 September 1752 was followed by 14 September 1752.
This is why Unix systems have <application>cal</application>
This is why Unix systems have the <command>cal</command> program
produce the following:
<programlisting>
% cal 9 1752
<screen>
$ <userinput>cal 9 1752</userinput>
September 1752
S M Tu W Th F S
1 2 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
</programlisting>
</screen>
</para>
<note>
<para>
SQL92 states that
<quote>Within the definition of a <quote>datetime literal</quote>,
the <quote>datetime value</quote>s are constrained by the
natural rules for dates and times
according to the Gregorian calendar</quote>.
Dates between 1752-09-03 and 1752-09-13, although eliminated in
some countries by Papal fiat, conform to
<quote>natural rules</quote> and are hence valid dates.
</para>
</note>
<note>
<para>
The SQL standard states that <quote>Within the definition of a
<quote>datetime literal</quote>, the <quote>datetime
value</quote>s are constrained by the natural rules for dates and
times according to the Gregorian calendar</quote>. Dates between
1752-09-03 and 1752-09-13, although eliminated in some countries
by Papal fiat, conform to <quote>natural rules</quote> and are
hence valid dates.
</para>
</note>
<para>
Different calendars have been developed in various parts of the
@ -1108,7 +1112,7 @@ Date/time details
calendar in 2637 BC.
The People's Republic of China uses the Gregorian calendar
for civil purposes. Chinese calendar is used for determining
for civil purposes. The Chinese calendar is used for determining
festivals.
</para>
</sect1>

16
doc/src/sgml/ddl.sgml
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@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ddl.sgml,v 1.8 2002/10/24 21:10:58 tgl Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ddl.sgml,v 1.9 2002/11/11 20:14:02 petere Exp $ -->
<chapter id="ddl">
<title>Data Definition</title>
@ -222,7 +222,7 @@ DROP TABLE products;
<para>
The identity (transaction ID) of the deleting transaction, or
zero for an undeleted tuple. It is possible for this field to
be nonzero in a visible tuple: that usually indicates that the
be nonzero in a visible tuple: That usually indicates that the
deleting transaction hasn't committed yet, or that an attempted
deletion was rolled back.
</para>
@ -353,7 +353,7 @@ CREATE TABLE products (
price numeric <emphasis>CONSTRAINT positive_price</emphasis> CHECK (price > 0)
);
</programlisting>
To specify a named constraint, use the key word
So, to specify a named constraint, use the key word
<literal>CONSTRAINT</literal> followed by an identifier followed
by the constraint definition.
</para>
@ -382,7 +382,7 @@ CREATE TABLE products (
</para>
<para>
We say that the first two are column constraints, whereas the
We say that the first two constraints are column constraints, whereas the
third one is a table constraint because it is written separately
from the column definitions. Column constraints can also be
written as table constraints, while the reverse is not necessarily
@ -931,7 +931,7 @@ WHERE c.altitude &gt; 500 and c.tableoid = p.oid;
<para>
In previous versions of <productname>PostgreSQL</productname>, the
default was not to get access to child tables. This was found to
be error prone and is also in violation of SQL99. Under the old
be error prone and is also in violation of the SQL standard. Under the old
syntax, to get the sub-tables you append <literal>*</literal> to the table name.
For example
<programlisting>
@ -1609,7 +1609,7 @@ REVOKE CREATE ON public FROM PUBLIC;
standard. Therefore, many users consider qualified names to
really consist of
<literal><replaceable>username</>.<replaceable>tablename</></literal>.
This is also supported by PostgreSQL if you create a per-user
This is how PostgreSQL will effectively behave if you create a per-user
schema for every user.
</para>
@ -1693,8 +1693,8 @@ DROP TABLE products CASCADE;
</screen>
and all the dependent objects will be removed. In this case, it
doesn't remove the orders table, it only removes the foreign key
constraint. (If you want to check what DROP ... CASCADE will do,
run DROP without CASCADE and read the NOTICEs.)
constraint. (If you want to check what <literal>DROP ... CASCADE</> will do,
run <command>DROP</> without <literal>CASCADE</> and read the <literal>NOTICE</> messages.)
</para>
<para>

11
doc/src/sgml/diskusage.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/diskusage.sgml,v 1.6 2002/10/16 22:06:33 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/diskusage.sgml,v 1.7 2002/11/11 20:14:02 petere Exp $
-->
<chapter id="diskusage">
@ -32,7 +32,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/diskusage.sgml,v 1.6 2002/10/16 22:06:33 pe
<para>
You can monitor disk space from three places: from
<application>psql</> using <command>VACUUM</> information, from
<application>psql</> using <application>contrib/dbsize</>, and from
<application>psql</> using <filename>contrib/dbsize</>, and from
the command line using <application>contrib/oid2name</>. Using
<application>psql</> on a recently vacuumed (or analyzed) database,
you can issue queries to see the disk usage of any table:
@ -94,13 +94,14 @@ play-# ORDER BY relpages DESC;
</para>
<para>
<application>dbsize</> loads functions into your database that allow
<filename>contrib/dbsize</> loads functions into your database that allow
you to find the size of a table or database from inside
<application>psql</> without the need for <command>VACUUM/ANALYZE.</>
</para>
<para>
You can also use <application>oid2name</> to show disk usage. See
<filename>README.oid2name</> for examples. It includes a script
You can also use <filename>contrib/oid2name</> to show disk usage. See
<filename>README.oid2name</> for examples. It includes a script that
shows disk usage for each database.
</para>
</sect1>

19
doc/src/sgml/dml.sgml
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@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/dml.sgml,v 1.2 2002/10/20 05:05:46 tgl Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/dml.sgml,v 1.3 2002/11/11 20:14:02 petere Exp $ -->
<chapter id="dml">
<title>Data Manipulation</title>
@ -23,10 +23,10 @@
<para>
When a table is created, it contains no data. The first thing to
do before a database can be of much use is to insert data. Data is
inserted one row at a time. This does not mean that there are no
means to <quote>bulk load</quote> many rows efficiently. But there
is no way to insert less than one row at a time. Even if you know
only some column values, a complete row must be created.
conceptually inserted one row at a time. Of course you can also
insert more than one row, but there is no way to insert less than
one row at a time. Even if you know only some column values, a
complete row must be created.
</para>
<para>
@ -84,6 +84,15 @@ INSERT INTO products (product_no, name, price) VALUES (1, 'Cheese', DEFAULT);
INSERT INTO products DEFAULT VALUES;
</programlisting>
</para>
<tip>
<para>
To do <quote>bulk loads</quote>, that is, inserting a lot of data,
take a look at the <command>COPY</command> command (see
&cite-reference;). It is not as flexible as the
<command>INSERT</command> command, but more efficient.
</para>
</tip>
</sect1>
<sect1 id="dml-update">

1390
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176
doc/src/sgml/indices.sgml
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@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/indices.sgml,v 1.37 2002/09/21 18:32:53 petere Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/indices.sgml,v 1.38 2002/11/11 20:14:03 petere Exp $ -->
<chapter id="indexes">
<title id="indexes-title">Indexes</title>
@ -432,172 +432,6 @@ SELECT am.amname AS acc_method,
</sect1>
<sect1 id="keys">
<title id="keys-title">Keys</title>
<para>
<note>
<title>Author</title>
<para>
Written by Herouth Maoz (<email>herouth@oumail.openu.ac.il</email>).
This originally appeared on the User's Mailing List on 1998-03-02
in response to the question:
"What is the difference between PRIMARY KEY and UNIQUE constraints?".
</para>
</note>
</para>
<para>
<literallayout>
Subject: Re: [QUESTIONS] PRIMARY KEY | UNIQUE
What's the difference between:
PRIMARY KEY(fields,...) and
UNIQUE (fields,...)
- Is this an alias?
- If PRIMARY KEY is already unique, then why
is there another kind of key named UNIQUE?
</literallayout>
</para>
<para>
A primary key is the field(s) used to identify a specific row. For example,
Social Security numbers identifying a person.
</para>
<para>
A simply UNIQUE combination of fields has nothing to do with identifying
the row. It's simply an integrity constraint. For example, I have
collections of links. Each collection is identified by a unique number,
which is the primary key. This key is used in relations.
</para>
<para>
However, my application requires that each collection will also have a
unique name. Why? So that a human being who wants to modify a collection
will be able to identify it. It's much harder to know, if you have two
collections named <quote>Life Science</quote>, the one tagged 24433 is the one you
need, and the one tagged 29882 is not.
</para>
<para>
So, the user selects the collection by its name. We therefore make sure,
within the database, that names are unique. However, no other table in the
database relates to the collections table by the collection Name. That
would be very inefficient.
</para>
<para>
Moreover, despite being unique, the collection name does not actually
define the collection! For example, if somebody decided to change the name
of the collection from <quote>Life Science</quote> to <quote>Biology</quote>, it will still be the
same collection, only with a different name. As long as the name is unique,
that's OK.
</para>
<para>
So:
<itemizedlist>
<listitem>
<para>
Primary key:
<itemizedlist spacing="compact" mark="bullet">
<listitem>
<para>
Is used for identifying the row and relating to it.
</para>
</listitem>
<listitem>
<para>
Is impossible (or hard) to update.
</para>
</listitem>
<listitem>
<para>
Should not allow null values.
</para>
</listitem>
</itemizedlist>
</para>
</listitem>
<listitem>
<para>
Unique field(s):
<itemizedlist spacing="compact" mark="bullet">
<listitem>
<para>
Are used as an alternative access to the row.
</para>
</listitem>
<listitem>
<para>
Are updatable, so long as they are kept unique.
</para>
</listitem>
<listitem>
<para>
Null values are acceptable.
</para>
</listitem>
</itemizedlist>
</para>
</listitem>
</itemizedlist>
</para>
<para>
As for why no non-unique keys are defined explicitly in standard
<acronym>SQL</acronym> syntax? Well, you
must understand that indexes are implementation-dependent.
<acronym>SQL</acronym> does not
define the implementation, merely the relations between data in the
database. <productname>PostgreSQL</productname> does allow
non-unique indexes, but indexes
used to enforce <acronym>SQL</acronym> keys are always unique.
</para>
<para>
Thus, you may query a table by any combination of its columns, despite the
fact that you don't have an index on these columns. The indexes are merely
an implementation aid that each <acronym>RDBMS</acronym> offers
you, in order to cause
commonly used queries to be done more efficiently.
Some <acronym>RDBMS</acronym> may give you
additional measures, such as keeping a key stored in main memory. They will
have a special command, for example
<synopsis>
CREATE MEMSTORE ON <replaceable>table</replaceable> COLUMNS <replaceable>cols</replaceable>
</synopsis>
(This is not an existing command, just an example.)
</para>
<para>
In fact, when you create a primary key or a unique combination of fields,
nowhere in the <acronym>SQL</acronym> specification does it say
that an index is created, nor that
the retrieval of data by the key is going to be more efficient than a
sequential scan!
</para>
<para>
So, if you want to use a combination of fields that is not unique as a
secondary key, you really don't have to specify anything - just start
retrieving by that combination! However, if you want to make the retrieval
efficient, you'll have to resort to the means your
<acronym>RDBMS</acronym> provider gives you
- be it an index, my imaginary <literal>MEMSTORE</literal> command, or an intelligent
<acronym>RDBMS</acronym>
that creates indexes without your knowledge based on the fact that you have
sent it many queries based on a specific combination of keys... (It learns
from experience).
</para>
</sect1>
<sect1 id="indexes-partial">
<title>Partial Indexes</title>
@ -876,8 +710,8 @@ CREATE UNIQUE INDEX tests_success_constraint ON tests (subject, target)
<para>
When indexes are not used, it can be useful for testing to force
their use. There are run-time parameters that can turn off
various plan types (described in the <citetitle>Administrator's
Guide</citetitle>). For instance, turning off sequential scans
various plan types (described in the &cite-admin;).
For instance, turning off sequential scans
(<varname>enable_seqscan</>) and nested-loop joins
(<varname>enable_nestloop</>), which are the most basic plans,
will force the system to use a different plan. If the system
@ -906,8 +740,8 @@ CREATE UNIQUE INDEX tests_success_constraint ON tests (subject, target)
again, two possibilities. The total cost is computed from the
per-row costs of each plan node times the selectivity estimate of
the plan node. The costs of the plan nodes can be tuned with
run-time parameters (described in the <citetitle>Administrator's
Guide</citetitle>). An inaccurate selectivity estimate is due to
run-time parameters (described in the &cite-admin;).
An inaccurate selectivity estimate is due to
insufficient statistics. It may be possible to help this by
tuning the statistics-gathering parameters (see <command>ALTER
TABLE</command> reference).

8
doc/src/sgml/install-win32.sgml
View File

@ -6,14 +6,6 @@
<secondary>on Windows</secondary>
</indexterm>
<abstract>
<para>
Build, installation, and use instructions for
<productname>PostgreSQL</productname> client libraries on
<productname>Windows</productname>
</para>
</abstract>
<para>
Although <productname>PostgreSQL</productname> is written for
Unix-like operating systems, the C client library

88
doc/src/sgml/installation.sgml
View File

@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/installation.sgml,v 1.110 2002/11/05 19:01:07 momjian Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/installation.sgml,v 1.111 2002/11/11 20:14:03 petere Exp $ -->
<chapter id="installation">
<title><![%standalone-include[<productname>PostgreSQL</>]]>
@ -8,6 +8,13 @@
<primary>installation</primary>
</indexterm>
<para>
This <![%standalone-include;[document.]]>
<![%standalone-ignore;[chapter.]]> describes the installation of
<productname>PostgreSQL</productname> from the source code
distribution.
</para>
<sect1 id="install-short">
<title>Short Version</title>
@ -131,27 +138,30 @@ su - postgres
<para>
To build the server programming language PL/Perl you need a full
Perl installation, including the <filename>libperl</filename>
library and the header files. Since PL/Perl is a shared
library and the header files. Since PL/Perl will be a shared
library, the <indexterm><primary>libperl</primary></indexterm>
<filename>libperl</filename> library must be a shared library
also on most platforms. At the time of this writing, this is
almost never the case in prebuilt Perl packages.
also on most platforms. This appears to be the default in
recent Perl versions, but it was not in earlier versions, and in
general it is the choice of whomever installed Perl at your
site.
</para>
<para>
If this difficulty arises in your situation, a message like this
will appear during the build to point out this fact:
If you don't have the shared library but you need one, a message
like this will appear during the build to point out this fact:
<screen>
*** Cannot build PL/Perl because libperl is not a shared library.
*** You might have to rebuild your Perl installation. Refer to
*** the documentation for details.
</screen>
(If you don't follow the on-screen output you will merely notice
the the PL/Perl library object will not be installed.) If you
see this, you will have to re-build and install
<productname>Perl</productname> manually to be able to build
PL/Perl. During the configuration process for
<productname>Perl</productname>, request a shared library.
that the PL/Perl library object, <filename>plperl.so</filename>
or similar, will not be installed.) If you see this, you will
have to rebuild and install <productname>Perl</productname>
manually to be able to build PL/Perl. During the configuration
process for <productname>Perl</productname>, request a shared
library.
</para>
</listitem>
@ -160,17 +170,18 @@ su - postgres
To build the Python interface module or the PL/Python server
programming language, you need a Python installation, including
the header files.
</para>
<para>
Since PL/Python is a shared library, the
Since PL/Python will be a shared library, the
<indexterm><primary>libpython</primary></indexterm>
<filename>libpython</filename> library must be a shared library
also on most platforms. This is not the case in a default
Python installation. If after building and installing you have
a file called <filename>plpython.so</filename> (possibly a
different extension), then everything went well. Otherwise you
should have seen a notice like this flying by:
Python installation.
</para>
<para>
If after building and installing you have a file called
<filename>plpython.so</filename> (possibly a different
extension), then everything went well. Otherwise you should
have seen a notice like this flying by:
<screen>
*** Cannot build PL/Python because libpython is not a shared library.
*** You might have to rebuild your Python installation. Refer to
@ -282,7 +293,7 @@ JAVACMD=$JAVA_HOME/bin/java
<primary>yacc</primary>
</indexterm>
<acronym>GNU</> <application>Flex</> and <application>Bison</>
<application>Flex</> and <application>Bison</>
are needed to build a CVS checkout or if you changed the actual
scanner and parser definition files. If you need them, be sure
to get <application>Flex</> 2.5.4 or later and
@ -373,7 +384,7 @@ JAVACMD=$JAVA_HOME/bin/java
<primary>pg_dumpall</primary>
</indexterm>
To dump your database installation, type:
To back up your database installation, type:
<screen>
<userinput>pg_dumpall &gt; <replaceable>outputfile</></userinput>
</screen>
@ -391,9 +402,16 @@ JAVACMD=$JAVA_HOME/bin/java
</para>
<para>
Make sure that you use the <command>pg_dumpall</> command
from the version you are currently running. &version;'s
<command>pg_dumpall</> should not be used on older databases.
To make the backup, you can use the <command>pg_dumpall</command>
command from the version you are currently running. For best
results, however, try to use the <command>pg_dumpall</command>
command from PostgreSQL &version;, since this version contains
bug fixes and improvements over older versions. While this
advice might seem idiosyncratic since you haven't installed the
new version yet, it is advisable to follow it if you plan to
install the new version in parallel with the old version. In
that case you can complete the installation normally and transfer
the data later. This will also decrease the downtime.
</para>
</step>
@ -453,12 +471,10 @@ JAVACMD=$JAVA_HOME/bin/java
</para>
<para>
You can also install the new version in parallel with the old one
to decrease the downtime. These topics are discussed at length in
<![%standalone-include[the <citetitle>Administrator's Guide</>,]]>
<![%standalone-ignore[<xref linkend="migration">,]]>
which you are encouraged
to read in any case.
These topics are discussed at length in <![%standalone-include[the
<citetitle>Administrator's Guide</>,]]> <![%standalone-ignore[<xref
linkend="migration">,]]> which you are encouraged to read in any
case.
</para>
</sect1>
@ -751,10 +767,6 @@ JAVACMD=$JAVA_HOME/bin/java
server-side language. You need to have root access to be able
to install the Python module at its default place
(<filename>/usr/lib/python<replaceable>x</>.<replaceable>y</></>).
To be able to use this option, you must have Python installed
and your system needs to support shared libraries. If you
instead want to build a new complete interpreter binary, you
will have to do it manually.
</para>
</listitem>
</varlistentry>
@ -763,7 +775,7 @@ JAVACMD=$JAVA_HOME/bin/java
<term><option>--with-tcl</option></term>
<listitem>
<para>
Builds components that require Tcl/Tk, which are
Build components that require Tcl/Tk, which are
<application>libpgtcl</>, <application>pgtclsh</>,
<application>pgtksh</application>,
and <application>PL/Tcl</>. But see below about
@ -1106,7 +1118,7 @@ All of PostgreSQL is successfully made. Ready to install.
</procedure>
<formalpara>
<title>Uninstall:</title>
<title>Uninstallation:</title>
<para>
To undo the installation use the command <command>gmake
uninstall</>. However, this will not remove any created directories.
@ -1192,7 +1204,7 @@ setenv LD_LIBRARY_PATH /usr/local/pgsql/lib
<para>
On <systemitem class="osname">Cygwin</systemitem>, put the library
directory on the <envar>PATH</envar> or move the
directory in the <envar>PATH</envar> or move the
<filename>.dll</filename> files into the <filename>bin/</filename>
directory.
</para>
@ -1735,7 +1747,7 @@ gunzip -c user.ps.gz \
<entry>7.3</entry>
<entry>2002-11-01,
7.1.3 Larry Rosenman (<email>ler@lerctr.org</email>),
7.1.1 and 7.1.2(8.0.0) Olivier Prenant (<email>ohp@pyrenet.fr</email>)
7.1.1 and 7.1.2(8.0.0) Olivier Prenant (<email>ohp@pyrenet.fr</email>)</entry>
<entry>see also <filename>doc/FAQ_SCO</filename></entry>
</row>
<row>

132
doc/src/sgml/keywords.sgml
View File

@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/keywords.sgml,v 2.7 2002/11/02 18:41:21 tgl Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/keywords.sgml,v 2.8 2002/11/11 20:14:03 petere Exp $ -->
<appendix id="sql-keywords-appendix">
<title><acronym>SQL</acronym> Key Words</title>
@ -232,13 +232,13 @@
</row>
<row>
<entry><token>ASSERTION</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
<row>
<entry><token>ASSIGNMENT</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>non-reserved</entry>
<entry></entry>
</row>
@ -262,7 +262,7 @@
</row>
<row>
<entry><token>AUTHORIZATION</token></entry>
<entry>non-reserved</entry>
<entry>reserved (can be function)</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -296,6 +296,12 @@
<entry>non-reserved</entry>
<entry>reserved</entry>
</row>
<row>
<entry><token>BIGINT</token></entry>
<entry>non-reserved (cannot be function or type)</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>BINARY</token></entry>
<entry>reserved (can be function)</entry>
@ -328,7 +334,7 @@
</row>
<row>
<entry><token>BOOLEAN</token></entry>
<entry></entry>
<entry>non-reserved (cannot be function or type)</entry>
<entry>reserved</entry>
<entry></entry>
</row>
@ -370,7 +376,7 @@
</row>
<row>
<entry><token>CALLED</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>non-reserved</entry>
<entry></entry>
</row>
@ -490,7 +496,7 @@
</row>
<row>
<entry><token>CLASS</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry></entry>
</row>
@ -680,6 +686,12 @@
<entry>reserved</entry>
<entry>reserved</entry>
</row>
<row>
<entry><token>CONVERSION</token></entry>
<entry>non-reserved</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>CONVERT</token></entry>
<entry>non-reserved (cannot be function or type)</entry>
@ -706,7 +718,7 @@
</row>
<row>
<entry><token>CREATE</token></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -832,7 +844,7 @@
</row>
<row>
<entry><token>DEALLOCATE</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -880,7 +892,7 @@
</row>
<row>
<entry><token>DEFINER</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>non-reserved</entry>
<entry></entry>
</row>
@ -988,7 +1000,7 @@
</row>
<row>
<entry><token>DOMAIN</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -1126,7 +1138,7 @@
</row>
<row>
<entry><token>EXTERNAL</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -1252,7 +1264,7 @@
</row>
<row>
<entry><token>GET</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -1276,7 +1288,7 @@
</row>
<row>
<entry><token>GRANT</token></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -1358,12 +1370,24 @@
<entry>reserved</entry>
<entry>reserved</entry>
</row>
<row>
<entry><token>IMMUTABLE</token></entry>
<entry>non-reserved</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>IMPLEMENTATION</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry></entry>
</row>
<row>
<entry><token>IMPLICIT</token></entry>
<entry>non-reserved</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>IN</token></entry>
<entry>reserved (can be function)</entry>
@ -1426,7 +1450,7 @@
</row>
<row>
<entry><token>INPUT</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -1462,13 +1486,13 @@
</row>
<row>
<entry><token>INT</token></entry>
<entry></entry>
<entry>non-reserved (cannot be function or type)</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
<row>
<entry><token>INTEGER</token></entry>
<entry></entry>
<entry>non-reserved (cannot be function or type)</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -1492,7 +1516,7 @@
</row>
<row>
<entry><token>INVOKER</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>non-reserved</entry>
<entry></entry>
</row>
@ -1642,13 +1666,13 @@
</row>
<row>
<entry><token>LOCALTIME</token></entry>
<entry></entry>
<entry>reserved</entry>
<entry>reserved</entry>
<entry></entry>
</row>
<row>
<entry><token>LOCALTIMESTAMP</token></entry>
<entry></entry>
<entry>reserved</entry>
<entry>reserved</entry>
<entry></entry>
</row>
@ -2056,7 +2080,7 @@
</row>
<row>
<entry><token>OVERLAY</token></entry>
<entry></entry>
<entry>non-reserved (cannot be function or type)</entry>
<entry>non-reserved</entry>
<entry></entry>
</row>
@ -2156,6 +2180,12 @@
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>PLACING</token></entry>
<entry>reserved</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>PLI</token></entry>
<entry></entry>
@ -2194,7 +2224,7 @@
</row>
<row>
<entry><token>PREPARE</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -2236,7 +2266,7 @@
</row>
<row>
<entry><token>PUBLIC</token></entry>
<entry>reserved (can be function)</entry>
<entry></entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -2254,9 +2284,15 @@
</row>
<row>
<entry><token>REAL</token></entry>
<entry>non-reserved (cannot be function or type)</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
<row>
<entry><token>RECHECK</token></entry>
<entry>non-reserved</entry>
<entry></entry>
<entry></entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
<row>
<entry><token>RECURSIVE</token></entry>
@ -2416,7 +2452,7 @@
</row>
<row>
<entry><token>ROW</token></entry>
<entry>non-reserved</entry>
<entry>non-reserved (cannot be function or type)</entry>
<entry>reserved</entry>
<entry></entry>
</row>
@ -2494,7 +2530,7 @@
</row>
<row>
<entry><token>SECURITY</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>non-reserved</entry>
<entry></entry>
</row>
@ -2578,13 +2614,13 @@
</row>
<row>
<entry><token>SIMILAR</token></entry>
<entry></entry>
<entry>reserved (can be function)</entry>
<entry>non-reserved</entry>
<entry></entry>
</row>
<row>
<entry><token>SIMPLE</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>non-reserved</entry>
<entry></entry>
</row>
@ -2596,7 +2632,7 @@
</row>
<row>
<entry><token>SMALLINT</token></entry>
<entry></entry>
<entry>non-reserved (cannot be function or type)</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -2672,6 +2708,12 @@
<entry>reserved</entry>
<entry></entry>
</row>
<row>
<entry><token>STABLE</token></entry>
<entry>non-reserved</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>START</token></entry>
<entry>non-reserved</entry>
@ -2714,6 +2756,18 @@
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>STORAGE</token></entry>
<entry>non-reserved</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>STRICT</token></entry>
<entry>non-reserved</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>STRUCTURE</token></entry>
<entry></entry>
@ -2914,7 +2968,7 @@
</row>
<row>
<entry><token>TREAT</token></entry>
<entry></entry>
<entry>non-reserved (cannot be function or type)</entry>
<entry>reserved</entry>
<entry></entry>
</row>
@ -3046,7 +3100,7 @@
</row>
<row>
<entry><token>USAGE</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>
@ -3092,6 +3146,12 @@
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>VALIDATOR</token></entry>
<entry>non-reserved</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>VALUE</token></entry>
<entry></entry>
@ -3140,6 +3200,12 @@
<entry>reserved</entry>
<entry>reserved</entry>
</row>
<row>
<entry><token>VOLATILE</token></entry>
<entry>non-reserved</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry><token>WHEN</token></entry>
<entry>reserved</entry>
@ -3178,7 +3244,7 @@
</row>
<row>
<entry><token>WRITE</token></entry>
<entry></entry>
<entry>non-reserved</entry>
<entry>reserved</entry>
<entry>reserved</entry>
</row>

17
doc/src/sgml/libpq.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/libpq.sgml,v 1.100 2002/11/10 00:14:22 momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/libpq.sgml,v 1.101 2002/11/11 20:14:03 petere Exp $
-->
<chapter id="libpq">
@ -2139,22 +2139,23 @@ for information on correct values for these environment variables.
<primary>password</primary>
<secondary>.pgpass</secondary>
</indexterm>
<filename>$HOME/.pgpass</filename> is a file that can contain passwords
to be used if the connection requires a password. This file should have the
format:
<screen>
The file <filename>.pgpass</filename> in the home directory is a file
that can contain passwords to be used if the connection requires a
password. This file should have the format:
<synopsis>
<replaceable>hostname</replaceable>:<replaceable>port</replaceable>:<replaceable>database</replaceable>:<replaceable>username</replaceable>:<replaceable>password</replaceable>
</screen>
</synopsis>
Any of these may be a literal name, or <literal>*</literal>, which matches
anything. The first match will be used so put more specific entries first.
Entries with <literal>:</literal> or <literal>\</literal> should be escaped
with <literal>\</literal>.
</para>
<para>
The permissions on <filename>$HOME/.pgpass</filename> must disallow any
The permissions on <filename>.pgpass</filename> must disallow any
access to world or group; achieve this by the command
<command>chmod 0600 $HOME/.pgaccess</command>.
<command>chmod 0600 .pgaccess</command>.
If the permissions are less strict than this, the file will be ignored.
</para>
</sect1>
<sect1 id="libpq-threading">

19
doc/src/sgml/maintenance.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.20 2002/11/11 20:14:03 petere Exp $
-->
<chapter id="maintenance">
@ -13,7 +13,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53
a regular basis to keep a <productname>PostgreSQL</productname>
installation running smoothly. The tasks discussed here are repetitive
in nature and can easily be automated using standard Unix tools such
as <filename>cron</filename> scripts. But it is the database
as <application>cron</application> scripts. But it is the database
administrator's responsibility to set up appropriate scripts, and to
check that they execute successfully.
</para>
@ -104,7 +104,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53
<command>UPDATE</> or <command>DELETE</> of a row does not
immediately remove the old <firstterm>tuple</> (version of the row).
This approach is necessary to gain the benefits of multiversion
concurrency control (see the <citetitle>User's Guide</>): the tuple
concurrency control (see the &cite-user;): the tuple
must not be deleted while it is still potentially visible to other
transactions. But eventually, an outdated or deleted tuple is no
longer of interest to any transaction. The space it occupies must be
@ -206,7 +206,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53
Although per-column tweaking of <command>ANALYZE</> frequency may not be
very productive, you may well find it worthwhile to do per-column
adjustment of the level of detail of the statistics collected by
<command>ANALYZE</>. Columns that are heavily used in WHERE clauses
<command>ANALYZE</>. Columns that are heavily used in <literal>WHERE</> clauses
and have highly irregular data distributions may require a finer-grain
data histogram than other columns. See <command>ALTER TABLE SET
STATISTICS</>.
@ -299,7 +299,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53
is exactly one billion transactions: if you wait longer, it's possible
that a tuple that was not quite old enough to be reassigned last time
is now more than two billion transactions old and has wrapped around
into the future --- ie, is lost to you. (Of course, it'll reappear
into the future --- i.e., is lost to you. (Of course, it'll reappear
after another two billion transactions, but that's no help.)
</para>
@ -311,17 +311,17 @@ $Header: /cvsroot/pgsql/doc/src/sgml/maintenance.sgml,v 1.19 2002/09/21 18:32:53
statistics in the system table <filename>pg_database</>. In particular,
the <filename>datfrozenxid</> field of a database's
<filename>pg_database</> row is updated at the completion of any
database-wide vacuum operation (ie, <command>VACUUM</> that does not
database-wide vacuum operation (i.e., <command>VACUUM</> that does not
name a specific table). The value stored in this field is the freeze
cutoff XID that was used by that <command>VACUUM</> command. All normal
XIDs older than this cutoff XID are guaranteed to have been replaced by
<literal>FrozenXID</> within that database. A convenient way to
examine this information is to execute the query
<informalexample>
<programlisting>
SELECT datname, age(datfrozenxid) FROM pg_database;
</programlisting>
</informalexample>
The <literal>age</> column measures the number of transactions from the
cutoff XID to the current transaction's XID.
</para>
@ -336,7 +336,7 @@ SELECT datname, age(datfrozenxid) FROM pg_database;
each database-wide <command>VACUUM</> automatically delivers a warning
if there are any <filename>pg_database</> entries showing an
<literal>age</> of more than 1.5 billion transactions, for example:
<informalexample>
<programlisting>
play=# vacuum;
WARNING: Some databases have not been vacuumed in 1613770184 transactions.
@ -344,7 +344,6 @@ WARNING: Some databases have not been vacuumed in 1613770184 transactions.
or you may have a wraparound failure.
VACUUM
</programlisting>
</informalexample>
</para>
<para>

4
doc/src/sgml/manage-ag.sgml
View File

@ -1,5 +1,5 @@
<!--
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<chapter id="managing-databases">
@ -27,7 +27,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/manage-ag.sgml,v 2.22 2002/10/24 17:48:54 p
database within the installation.) More accurately, a database is
a collection of schemas and the schemas contain the tables,
functions, etc. So the full hierarchy is:
server-database-schema-table (or something else instead of a
server, database, schema, table (or something else instead of a
table).
</para>

362
doc/src/sgml/monitoring.sgml
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@ -1,12 +1,12 @@
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-->
<chapter id="monitoring">
<title>Monitoring Database Activity</title>
<para>
A database administrator frequently wonders <quote>what is the system
A database administrator frequently wonders, <quote>What is the system
doing right now?</quote>
This chapter discusses how to find that out.
</para>
@ -19,7 +19,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/monitoring.sgml,v 1.14 2002/09/21 18:32:53
<command>ps</> and <command>top</>. Also, once one has identified a
poorly-performing query, further investigation may be needed using
<productname>PostgreSQL</productname>'s <command>EXPLAIN</> command.
The <citetitle>User's Guide</citetitle> discusses <command>EXPLAIN</>
The &cite-user; discusses <command>EXPLAIN</>
and other methods for understanding the behavior of an individual
query.
</para>
@ -64,8 +64,8 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
The user, database, and connection source host items remain the same for
the life of the client connection, but the activity indicator changes.
The activity may be <literal>idle</> (ie, waiting for a client command),
<literal>idle in transaction</> (waiting for client inside a BEGIN block),
The activity may be <literal>idle</> (i.e., waiting for a client command),
<literal>idle in transaction</> (waiting for client inside a <command>BEGIN</> block),
or a command type name such as <literal>SELECT</>. Also,
<literal>waiting</> is attached if the server is presently waiting
on a lock held by another server process. In the above example we can infer
@ -149,7 +149,7 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
<varname>STATS_BLOCK_LEVEL</varname>,
and <varname>STATS_ROW_LEVEL</varname>
default to <literal>false</>, no statistics are actually collected
in the default configuration! You must turn one or more of them on
in the default configuration. You must turn one or more of them on
before you will get useful results from the statistical display
functions.
</para>
@ -162,8 +162,9 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
<para>
Several predefined views are available to show the results of
statistics collection. Alternatively, one can build custom views
using the underlying statistics functions.
statistics collection, listed in <xref
linkend="monitoring-stats-views-table">. Alternatively, one can
build custom views using the underlying statistics functions.
</para>
<para>
@ -172,8 +173,8 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
Each individual server process transmits new access counts to the collector
just before waiting for another client command; so a query still in
progress does not affect the displayed totals. Also, the collector itself
emits new totals at most once per <varname>pgstat_stat_interval</varname> (500 milliseconds
by default). So the displayed totals lag behind actual activity.
emits new totals at most once per <varname>pgstat_stat_interval</varname> milliseconds
(500 by default). So the displayed totals lag behind actual activity.
</para>
<para>
@ -190,7 +191,7 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
block.
</para>
<table>
<table id="monitoring-stats-views-table">
<title>Standard Statistics Views</title>
<tgroup cols="2">
@ -204,9 +205,9 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
<tbody>
<row>
<entry><structname>pg_stat_activity</></entry>
<entry>One row per server process, showing process <acronym>PID</>, database,
<entry>One row per server process, showing process <acronym>ID</>, database,
user, and current query. The current query column is only available
to superusers; for others it reads as NULL. (Note that because of
to superusers; for others it reads as null. (Note that because of
the collector's reporting delay, current query will only be up-to-date
for long-running queries.)</entry>
</row>
@ -215,7 +216,7 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
<entry><structname>pg_stat_database</></entry>
<entry>One row per database, showing number of active backends,
total transactions committed and total rolled back in that database,
total disk blocks read, and total number of buffer hits (ie, block
total disk blocks read, and total number of buffer hits (i.e., block
read requests avoided by finding the block already in buffer cache).
</entry>
</row>
@ -230,13 +231,13 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
<row>
<entry><structname>pg_stat_sys_tables</></entry>
<entry>Same as pg_stat_all_tables, except that only system tables
<entry>Same as <structname>pg_stat_all_tables</>, except that only system tables
are shown.</entry>
</row>
<row>
<entry><structname>pg_stat_user_tables</></entry>
<entry>Same as pg_stat_all_tables, except that only user tables
<entry>Same as <structname>pg_stat_all_tables</>, except that only user tables
are shown.</entry>
</row>
@ -244,20 +245,20 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
<entry><structname>pg_stat_all_indexes</></entry>
<entry>For each index in the current database, the total number
of index scans that have used that index, the number of index tuples
read, and the number of successfully fetched heap tuples (this may
be less when there are index entries pointing to expired heap tuples).
read, and the number of successfully fetched heap tuples. (This may
be less when there are index entries pointing to expired heap tuples.)
</entry>
</row>
<row>
<entry><structname>pg_stat_sys_indexes</></entry>
<entry>Same as pg_stat_all_indexes, except that only indexes on
<entry>Same as <structname>pg_stat_all_indexes</>, except that only indexes on
system tables are shown.</entry>
</row>
<row>
<entry><structname>pg_stat_user_indexes</></entry>
<entry>Same as pg_stat_all_indexes, except that only indexes on
<entry>Same as <structname>pg_stat_all_indexes</>, except that only indexes on
user tables are shown.</entry>
</row>
@ -339,18 +340,19 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
</para>
<para>
Other ways of looking at the statistics can be set up by writing queries
that use the same underlying statistics access functions as these standard
views do. The per-database access functions accept a database OID to
identify which database to report on. The per-table and per-index
functions accept a table or index OID (note that only tables and indexes
in the current
Other ways of looking at the statistics can be set up by writing
queries that use the same underlying statistics access functions as
these standard views do. These functions are listed in <xref
linkend="monitoring-stats-funcs-table">. The per-database access
functions accept a database OID to identify which database to
report on. The per-table and per-index functions accept a table or
index OID (note that only tables and indexes in the current
database can be seen with these functions). The per-backend access
functions accept a backend ID number, which ranges from one to the number
of currently active backends.
functions accept a backend ID number, which ranges from one to the
number of currently active backends.
</para>
<table>
<table id="monitoring-stats-funcs-table">
<title>Statistics Access Functions</title>
<tgroup cols="3">
@ -531,11 +533,14 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
</tgroup>
</table>
<para>
Note: blocks_fetched minus blocks_hit gives the number of kernel read()
calls issued for the table, index, or database; but the actual number of
physical reads is usually lower due to kernel-level buffering.
</para>
<note>
<para>
Blocks_fetched minus blocks_hit gives the number of kernel
<function>read()</> calls issued for the table, index, or
database; but the actual number of physical reads is usually
lower due to kernel-level buffering.
</para>
</note>
<para>
The function <function>pg_stat_get_backend_idset</function> provides
@ -552,157 +557,168 @@ FROM (SELECT pg_stat_get_backend_idset() AS backendid) AS S;
</sect2>
</sect1>
<sect1 id="monitoring-locks">
<title>Viewing Locks</title>
<sect1 id="monitoring-locks">
<title>Viewing Locks</title>
<para>
Another useful tool for monitoring database activity is the
<literal>pg_locks</literal> system catalog. This allows the
database administrator to view information about the outstanding
locks in the lock manager. For example, this capability can be used
to:
<itemizedlist>
<listitem>
<para>
View all the locks currently outstanding, all the locks on
relations in a particular database, all the locks on a
particular relation, or all the locks held by a particular
<productname>PostgreSQL</productname> session.
</para>
</listitem>
<listitem>
<para>
View the relation in the current database with the most
ungranted locks (which might be a source of contention among
database clients).
</para>
</listitem>
<listitem>
<para>
Determine the effect of lock contention on overall database
performance, as well as the extent to which contention varies
with overall database traffic.
</para>
</listitem>
</itemizedlist>
For more information on locking and managing concurrency with
<productname>PostgreSQL</productname>, refer to the &cite-user;.
</para>
<note>
<para>
Another useful tool for monitoring database activity is the
<literal>pg_locks</literal> system catalog. This allows the
database administrator to view information about the outstanding
locks in the lock manager. For example, this capability can be
used to:
<itemizedlist>
<listitem>
<para>
View all the locks currently outstanding, all the locks on
relations in a particular database, all the locks on a
particular relation, or all the locks held by a particular
<productname>PostgreSQL</productname> backend.
</para>
</listitem>
<listitem>
<para>
View the relation in the current database with the most
un-granted locks (which might be a source of contention among
database clients).
</para>
</listitem>
<listitem>
<para>
Determine the effect of lock contention on overall database
performance, as well as the extent to which contention varies
with overall database traffic.
</para>
</listitem>
</itemizedlist>
For more information on locking and managing concurrency with
<productname>PostgreSQL</productname>, refer to the
<citetitle>Administrator's Guide</citetitle>.
When the <literal>pg_locks</literal> view is accessed, the
internal lock manager data structures are momentarily locked, and
a copy is made for the view to display. This ensures that the
view produces a consistent set of results, while not blocking
normal lock manager operations longer than necessary. Nonetheless
there could be some impact on database performance if this view is
examined often.
</para>
</note>
<note>
<para>
When the <literal>pg_locks</literal> view is accessed, the
internal lock manager data structures are momentarily locked,
and a copy is made for the view to display. This ensures that
the view produces a consistent set of results, while not blocking
normal lock manager operations longer than necessary. Nonetheless
there could be some impact on database performance if this view is
examined often.
</para>
</note>
<para>
<xref linkend="monitoring-locks-table"> shows the definition of the
<literal>pg_locks</literal> columns. The
<literal>pg_locks</literal> view contains one row per lockable
object and requested lock mode. Thus, the same lockable object may
appear many times, if multiple transactions are holding or waiting
for locks on it. A lockable object is either a relation or a
transaction ID. (Note that this view includes only table-level
locks, not row-level ones. If a transaction is waiting for a
row-level lock, it will appear in the view as waiting for the
transaction ID of the current holder of that row lock.)
</para>
<para>
The <literal>pg_locks</literal> view contains one row per lockable
object and requested lock mode. Thus, the same lockable object
may appear many times, if multiple transactions are holding or
waiting for locks on it. A lockable object is either a relation
or a transaction ID. (Note that this view includes only table-level
locks, not row-level ones. If a transaction is waiting for a
row-level lock, it will appear in the view as waiting for the
transaction ID of the current holder of that row lock.)
</para>
<table id="monitoring-locks-table">
<title>Lock Status System View</title>
<table>
<title>Lock Status System View</title>
<tgroup cols="3">
<thead>
<row>
<entry>Column Name</entry>
<entry>Type</entry>
<entry>Description</entry>
</row>
</thead>
<tgroup cols="3">
<thead>
<row>
<entry>Column Name</entry>
<entry>Type</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><structfield>relation</structfield></entry>
<entry><type>oid</type></entry>
<entry>
The OID of the locked relation, or null if the lockable object
is a transaction ID. This column can be joined with the
<literal>pg_class</literal> system catalog to get more
information on the locked relation. Note however that this
will only work for relations in the current database (those for
which the <structfield>database</structfield> column is either
the current database's OID or zero).
</entry>
</row>
<tbody>
<row>
<entry><structfield>relation</structfield></entry>
<entry><type>oid</type></entry>
<entry>The OID of the locked relation, or NULL if the lockable
object is a transaction ID. This column can be joined
with the <literal>pg_class</literal> system catalog to get more
information on the locked relation. Note however that this will
only work for relations in the current database (those for which
the <structfield>database</structfield> column is either the
current database's OID or zero).
</entry>
</row>
<row>
<entry><structfield>database</structfield></entry>
<entry><type>oid</type></entry>
<entry>
The OID of the database in which the locked relation exists, or
null if the lockable object is a transaction ID. If the lock
is on a globally-shared table, this field will be zero. This
column can be joined with the <literal>pg_database</literal>
system catalog to get more information on the locked object's
database.
</entry>
</row>
<row>
<entry><structfield>database</structfield></entry>
<entry><type>oid</type></entry>
<entry>The OID of the database in which the locked relation
exists, or NULL if the lockable object is a transaction ID.
If the lock is on a globally-shared table, this field will be
zero. This
column can be joined with the <literal>pg_database</literal>
system catalog to get more information on the locked object's
database.
</entry>
</row>
<row>
<entry><structfield>transaction</structfield></entry>
<entry><type>xid</type></entry>
<entry>
The ID of a transaction, or null if the lockable object is a
relation. Every transaction holds an exclusive lock on its
transaction ID for its entire duration. If one transaction
finds it necessary to wait specifically for another
transaction, it does so by attempting to acquire share lock on
the other transaction ID. That will succeed only when the
other transaction terminates and releases its locks.
</entry>
</row>
<row>
<entry><structfield>transaction</structfield></entry>
<entry><type>xid</type></entry>
<entry>The ID of a transaction, or NULL if the lockable object
is a relation. Every transaction holds an exclusive lock on its
transaction ID for its entire duration. If one transaction finds
it necessary to wait specifically for another transaction, it
does so by attempting to acquire share lock on the other transaction
ID. That will succeed only when the other transaction terminates
and releases its locks.
</entry>
</row>
<row>
<entry><structfield>pid</structfield></entry>
<entry><type>integer</type></entry>
<entry>
The process ID of the <productname>PostgreSQL</productname>
backend belonging to the session that has acquired or is
attempting to acquire the lock. If you have enabled the
statistics collector, this column can be joined with the
<literal>pg_stat_activity</literal> view to get more
information on the backend holding or waiting to hold the
lock.
</entry>
</row>
<row>
<entry><structfield>pid</structfield></entry>
<entry><type>int4</type></entry>
<entry>The process ID of the
<productname>PostgreSQL</productname> backend that has
acquired or is attempting to acquire the lock. If you have
enabled the statistics collector, this column can be joined
with the <literal>pg_stat_activity</literal> view to get
more information on the backend holding or waiting to hold the
lock.</entry>
</row>
<row>
<entry><structfield>mode</structfield></entry>
<entry><type>text</type></entry>
<entry>
The mode of the requested or held lock on the lockable
object. For more information on the different lock modes
available in <productname>PostgreSQL</productname>, refer to
the &cite-user;.
</entry>
</row>
<row>
<entry><structfield>mode</structfield></entry>
<entry><type>text</type></entry>
<entry>The mode of the requested or held lock on the lockable
object. For more information on the
different lock modes available in
<productname>PostgreSQL</productname>, refer to the
<citetitle>User's Guide</citetitle>.</entry>
</row>
<row>
<entry><structfield>isgranted</structfield></entry>
<entry><type>bool</type></entry>
<entry>True if this lock has been granted (is held by this
backend). False indicates that this backend is currently
waiting to acquire this lock, which implies that some other
backend is holding a conflicting lock mode on the same lockable
object. This backend will sleep until the other lock is released
(or a deadlock situation is detected). A single backend can be
waiting to acquire at most one lock at a time.</entry>
</row>
</tbody>
</tgroup>
</table>
</sect1>
<row>
<entry><structfield>isgranted</structfield></entry>
<entry><type>boolean</type></entry>
<entry>
True if this lock has been granted (is held by this session).
False indicates that this session is currently waiting to
acquire this lock, which implies that some other session is
holding a conflicting lock mode on the same lockable object.
This backend will sleep until the other lock is released (or a
deadlock situation is detected). A single backend can be
waiting to acquire at most one lock at a time.
</entry>
</row>
</tbody>
</tgroup>
</table>
</sect1>
</chapter>
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131
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@ -1,5 +1,5 @@
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$Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.29 2002/11/11 20:14:03 petere Exp $
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<chapter id="mvcc">
@ -9,24 +9,23 @@ $Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.28 2002/09/21 18:32:53 petere
<primary>concurrency</primary>
</indexterm>
<abstract>
<para>
Multiversion Concurrency Control
(MVCC)
is an advanced technique for improving database performance in a
multiuser environment.
Vadim Mikheev (<email>vadim@krs.ru</email>) provided
the implementation for <productname>PostgreSQL</productname>.
</para>
</abstract>
<para>
This chapter describes the behavior of the PostgreSQL database
system when two or more sessions try to access the same data at the
same time. The goals in that situation are to allow efficient
access for all sessions while maintaining strict data integrity.
Every developer of database applications should be familiar with
the topics covered in this chapter.
</para>
<sect1 id="mvcc-intro">
<title>Introduction</title>
<para>
Unlike most other database systems which use locks for concurrency control,
Unlike traditional database systems which use locks for concurrency control,
<productname>PostgreSQL</productname>
maintains data consistency by using a multiversion model.
maintains data consistency by using a multiversion model
(Multiversion Concurrency Control, <acronym>MVCC</acronym>).
This means that while querying a database each transaction sees
a snapshot of data (a <firstterm>database version</firstterm>)
as it was some
@ -56,7 +55,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.28 2002/09/21 18:32:53 petere
<title>Transaction Isolation</title>
<para>
The <acronym>ANSI</acronym>/<acronym>ISO</acronym> <acronym>SQL</acronym>
The <acronym>SQL</acronym>
standard defines four levels of transaction
isolation in terms of three phenomena that must be prevented
between concurrent transactions.
@ -65,8 +64,8 @@ $Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.28 2002/09/21 18:32:53 petere
<variablelist>
<varlistentry>
<term>
dirty reads
<indexterm><primary>dirty reads</primary></indexterm>
dirty read
<indexterm><primary>dirty read</primary></indexterm>
</term>
<listitem>
<para>
@ -77,8 +76,8 @@ $Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.28 2002/09/21 18:32:53 petere
<varlistentry>
<term>
non-repeatable reads
<indexterm><primary>non-repeatable reads</primary></indexterm>
nonrepeatable read
<indexterm><primary>nonrepeatable read</primary></indexterm>
</term>
<listitem>
<para>
@ -92,7 +91,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.28 2002/09/21 18:32:53 petere
<varlistentry>
<term>
phantom read
<indexterm><primary>phantom reads</primary></indexterm>
<indexterm><primary>phantom read</primary></indexterm>
</term>
<listitem>
<para>
@ -111,6 +110,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.28 2002/09/21 18:32:53 petere
</indexterm>
The four transaction isolation levels and the corresponding
behaviors are described in <xref linkend="mvcc-isolevel-table">.
</para>
<table tocentry="1" id="mvcc-isolevel-table">
<title><acronym>SQL</acronym> Transaction Isolation Levels</title>
@ -125,7 +125,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.28 2002/09/21 18:32:53 petere
Dirty Read
</entry>
<entry>
Non-Repeatable Read
Nonrepeatable Read
</entry>
<entry>
Phantom Read
@ -195,15 +195,13 @@ $Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.28 2002/09/21 18:32:53 petere
</tbody>
</tgroup>
</table>
</para>
<para>
<productname>PostgreSQL</productname>
offers the read committed and serializable isolation levels.
</para>
</sect1>
<sect1 id="xact-read-committed">
<sect2 id="xact-read-committed">
<title>Read Committed Isolation Level</title>
<indexterm>
@ -229,7 +227,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.28 2002/09/21 18:32:53 petere
</para>
<para>
<command>UPDATE</command>, <command>DELETE</command> and <command>SELECT
<command>UPDATE</command>, <command>DELETE</command>, and <command>SELECT
FOR UPDATE</command> commands behave the same as <command>SELECT</command>
in terms of searching for target rows: they will only find target rows
that were committed as of the query start time. However, such a target
@ -287,9 +285,9 @@ COMMIT;
be necessary to guarantee a more rigorously consistent view of the
database than the Read Committed mode provides.
</para>
</sect1>
</sect2>
<sect1 id="xact-serializable">
<sect2 id="xact-serializable">
<title>Serializable Isolation Level</title>
<indexterm>
@ -316,13 +314,13 @@ COMMIT;
committed.) This is different from Read Committed in that the
<command>SELECT</command>
sees a snapshot as of the start of the transaction, not as of the start
of the current query within the transaction. Successive
of the current query within the transaction. Thus, successive
<command>SELECT</command>s within a single transaction always see the same
data.
</para>
<para>
<command>UPDATE</command>, <command>DELETE</command> and <command>SELECT
<command>UPDATE</command>, <command>DELETE</command>, and <command>SELECT
FOR UPDATE</command> commands behave the same as <command>SELECT</command>
in terms of searching for target rows: they will only find target rows
that were committed as of the transaction start time. However, such a
@ -370,7 +368,8 @@ ERROR: Can't serialize access due to concurrent update
a transaction performs several successive queries that must see
identical views of the database.
</para>
</sect1>
</sect2>
</sect1>
<sect1 id="explicit-locking">
<title>Explicit Locking</title>
@ -421,8 +420,7 @@ ERROR: Can't serialize access due to concurrent update
To examine a list of the currently outstanding locks in a
database server, use the <literal>pg_locks</literal> system
view. For more information on monitoring the status of the lock
manager subsystem, refer to the <citetitle>Administrator's
Guide</citetitle>.
manager subsystem, refer to the &cite-admin;.
</para>
<variablelist>
@ -647,14 +645,14 @@ ERROR: Can't serialize access due to concurrent update
<para>
Use of explicit locking can cause <firstterm>deadlocks</>, wherein
two (or more) transactions each hold locks that the other wants.
For example, if transaction 1 acquires exclusive lock on table A
and then tries to acquire exclusive lock on table B, while transaction
2 has already exclusive-locked table B and now wants exclusive lock
For example, if transaction 1 acquires an exclusive lock on table A
and then tries to acquire an exclusive lock on table B, while transaction
2 has already exclusive-locked table B and now wants an exclusive lock
on table A, then neither one can proceed.
<productname>PostgreSQL</productname> automatically detects deadlock
situations and resolves them by aborting one of the transactions
involved, allowing the other(s) to complete. (Exactly which transaction
will be aborted is difficult to predict, and should not be relied on.)
will be aborted is difficult to predict and should not be relied on.)
</para>
<para>
@ -678,7 +676,7 @@ ERROR: Can't serialize access due to concurrent update
</sect1>
<sect1 id="applevel-consistency">
<title>Data consistency checks at the application level</title>
<title>Data Consistency Checks at the Application Level</title>
<para>
Because readers in <productname>PostgreSQL</productname>
@ -718,11 +716,10 @@ ERROR: Can't serialize access due to concurrent update
<note>
<para>
Before version 6.5 <productname>PostgreSQL</productname>
used read-locks and so the
above consideration is also the case
when upgrading to 6.5 (or higher) from previous
<productname>PostgreSQL</productname> versions.
Before version 6.5 <productname>PostgreSQL</productname> used
read locks, and so the above consideration is also the case when
upgrading from <productname>PostgreSQL</productname> versions
prior to 6.5.
</para>
</note>
</para>
@ -732,7 +729,7 @@ ERROR: Can't serialize access due to concurrent update
example, a banking application might wish to check that the sum of
all credits in one table equals the sum of debits in another table,
when both tables are being actively updated. Comparing the results of two
successive SELECT SUM(...) commands will not work reliably under
successive <literal>SELECT SUM(...)</literal> commands will not work reliably under
Read Committed mode, since the second query will likely include the results
of transactions not counted by the first. Doing the two sums in a
single serializable transaction will give an accurate picture of the
@ -758,7 +755,8 @@ ERROR: Can't serialize access due to concurrent update
the table are still running --- but if the snapshot seen by the
transaction predates obtaining the lock, it may predate some now-committed
changes in the table. A serializable transaction's snapshot is actually
frozen at the start of its first query (SELECT/INSERT/UPDATE/DELETE), so
frozen at the start of its first query (<literal>SELECT</>, <literal>INSERT</>,
<literal>UPDATE</>, or <literal>DELETE</>), so
it's possible to obtain explicit locks before the snapshot is
frozen.
</para>
@ -781,12 +779,26 @@ ERROR: Can't serialize access due to concurrent update
<variablelist>
<varlistentry>
<term>
<acronym>GiST</acronym> and R-Tree indexes
B-tree indexes
</term>
<listitem>
<para>
Short-term share/exclusive page-level locks are used for
read/write access. Locks are released immediately after each
index tuple is fetched or inserted. B-tree indexes provide
the highest concurrency without deadlock conditions.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<acronym>GiST</acronym> and R-tree indexes
</term>
<listitem>
<para>
Share/exclusive index-level locks are used for read/write access.
Locks are released after statement is done.
Locks are released after the statement (command) is done.
</para>
</listitem>
</varlistentry>
@ -797,31 +809,10 @@ ERROR: Can't serialize access due to concurrent update
</term>
<listitem>
<para>
Share/exclusive page-level locks are used for read/write access.
Locks are released after page is processed.
</para>
<para>
Page-level locks provide better concurrency than index-level ones
but are subject to deadlocks.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
B-tree indexes
</term>
<listitem>
<para>
Short-term share/exclusive page-level locks are used for
read/write access. Locks are released immediately after each index
tuple is fetched/inserted.
</para>
<para>
B-tree indexes provide the highest concurrency without deadlock
conditions.
Share/exclusive page-level locks are used for read/write
access. Locks are released after the page is processed.
Page-level locks provide better concurrency than index-level
ones but are liable to deadlocks.
</para>
</listitem>
</varlistentry>

240
doc/src/sgml/perform.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.21 2002/09/21 18:32:53 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.22 2002/11/11 20:14:03 petere Exp $
-->
<chapter id="performance-tips">
@ -32,30 +32,30 @@ $Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.21 2002/09/21 18:32:53 pet
<itemizedlist>
<listitem>
<para>
Estimated start-up cost (time expended before output scan can start,
e.g., time to do the sorting in a SORT node).
Estimated start-up cost (Time expended before output scan can start,
e.g., time to do the sorting in a sort node.)
</para>
</listitem>
<listitem>
<para>
Estimated total cost (if all tuples are retrieved, which they may not
be --- a query with a LIMIT will stop short of paying the total cost,
for example).
Estimated total cost (If all rows are retrieved, which they may not
be --- a query with a <literal>LIMIT</> clause will stop short of paying the total cost,
for example.)
</para>
</listitem>
<listitem>
<para>
Estimated number of rows output by this plan node (again, only if
executed to completion).
Estimated number of rows output by this plan node (Again, only if
executed to completion.)
</para>
</listitem>
<listitem>
<para>
Estimated average width (in bytes) of rows output by this plan
node.
node
</para>
</listitem>
</itemizedlist>
@ -64,9 +64,9 @@ $Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.21 2002/09/21 18:32:53 pet
<para>
The costs are measured in units of disk page fetches. (CPU effort
estimates are converted into disk-page units using some
fairly arbitrary fudge-factors. If you want to experiment with these
fairly arbitrary fudge factors. If you want to experiment with these
factors, see the list of run-time configuration parameters in the
<citetitle>Administrator's Guide</citetitle>.)
&cite-admin;.)
</para>
<para>
@ -74,17 +74,17 @@ $Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.21 2002/09/21 18:32:53 pet
the cost of all its child nodes. It's also important to realize that
the cost only reflects things that the planner/optimizer cares about.
In particular, the cost does not consider the time spent transmitting
result tuples to the frontend --- which could be a pretty dominant
result rows to the frontend --- which could be a pretty dominant
factor in the true elapsed time, but the planner ignores it because
it cannot change it by altering the plan. (Every correct plan will
output the same tuple set, we trust.)
output the same row set, we trust.)
</para>
<para>
Rows output is a little tricky because it is <emphasis>not</emphasis> the
number of rows
processed/scanned by the query --- it is usually less, reflecting the
estimated selectivity of any WHERE-clause constraints that are being
estimated selectivity of any <literal>WHERE</>-clause constraints that are being
applied at this node. Ideally the top-level rows estimate will
approximate the number of rows actually returned, updated, or deleted
by the query.
@ -92,44 +92,44 @@ $Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.21 2002/09/21 18:32:53 pet
<para>
Here are some examples (using the regress test database after a
vacuum analyze, and 7.3 development sources):
<literal>VACUUM ANALYZE</>, and 7.3 development sources):
<programlisting>
<programlisting>
regression=# EXPLAIN SELECT * FROM tenk1;
QUERY PLAN
-------------------------------------------------------------
Seq Scan on tenk1 (cost=0.00..333.00 rows=10000 width=148)
</programlisting>
</programlisting>
</para>
<para>
This is about as straightforward as it gets. If you do
<programlisting>
<programlisting>
SELECT * FROM pg_class WHERE relname = 'tenk1';
</programlisting>
</programlisting>
you will find out that <classname>tenk1</classname> has 233 disk
pages and 10000 tuples. So the cost is estimated at 233 page
reads, defined as 1.0 apiece, plus 10000 * <varname>cpu_tuple_cost</varname> which is
currently 0.01 (try <command>show cpu_tuple_cost</command>).
pages and 10000 rows. So the cost is estimated at 233 page
reads, defined as costing 1.0 apiece, plus 10000 * <varname>cpu_tuple_cost</varname> which is
currently 0.01 (try <command>SHOW cpu_tuple_cost</command>).
</para>
<para>
Now let's modify the query to add a WHERE condition:
Now let's modify the query to add a <literal>WHERE</> condition:
<programlisting>
<programlisting>
regression=# EXPLAIN SELECT * FROM tenk1 WHERE unique1 &lt; 1000;
QUERY PLAN
------------------------------------------------------------
Seq Scan on tenk1 (cost=0.00..358.00 rows=1033 width=148)
Filter: (unique1 &lt; 1000)
</programlisting>
</programlisting>
The estimate of output rows has gone down because of the WHERE clause.
The estimate of output rows has gone down because of the <literal>WHERE</> clause.
However, the scan will still have to visit all 10000 rows, so the cost
hasn't decreased; in fact it has gone up a bit to reflect the extra CPU
time spent checking the WHERE condition.
time spent checking the <literal>WHERE</> condition.
</para>
<para>
@ -144,26 +144,26 @@ regression=# EXPLAIN SELECT * FROM tenk1 WHERE unique1 &lt; 1000;
<para>
Modify the query to restrict the condition even more:
<programlisting>
<programlisting>
regression=# EXPLAIN SELECT * FROM tenk1 WHERE unique1 &lt; 50;
QUERY PLAN
-------------------------------------------------------------------------------
Index Scan using tenk1_unique1 on tenk1 (cost=0.00..179.33 rows=49 width=148)
Index Cond: (unique1 &lt; 50)
</programlisting>
</programlisting>
and you will see that if we make the WHERE condition selective
and you will see that if we make the <literal>WHERE</> condition selective
enough, the planner will
eventually decide that an index scan is cheaper than a sequential scan.
This plan will only have to visit 50 tuples because of the index,
This plan will only have to visit 50 rows because of the index,
so it wins despite the fact that each individual fetch is more expensive
than reading a whole disk page sequentially.
</para>
<para>
Add another clause to the WHERE condition:
Add another clause to the <literal>WHERE</> condition:
<programlisting>
<programlisting>
regression=# EXPLAIN SELECT * FROM tenk1 WHERE unique1 &lt; 50 AND
regression-# stringu1 = 'xxx';
QUERY PLAN
@ -171,11 +171,11 @@ regression-# stringu1 = 'xxx';
Index Scan using tenk1_unique1 on tenk1 (cost=0.00..179.45 rows=1 width=148)
Index Cond: (unique1 &lt; 50)
Filter: (stringu1 = 'xxx'::name)
</programlisting>
</programlisting>
The added clause <literal>stringu1 = 'xxx'</literal> reduces the
output-rows estimate, but not the cost because we still have to visit the
same set of tuples. Notice that the <literal>stringu1</> clause
same set of rows. Notice that the <literal>stringu1</> clause
cannot be applied as an index condition (since this index is only on
the <literal>unique1</> column). Instead it is applied as a filter on
the rows retrieved by the index. Thus the cost has actually gone up
@ -185,7 +185,7 @@ regression-# stringu1 = 'xxx';
<para>
Let's try joining two tables, using the fields we have been discussing:
<programlisting>
<programlisting>
regression=# EXPLAIN SELECT * FROM tenk1 t1, tenk2 t2 WHERE t1.unique1 &lt; 50
regression-# AND t1.unique2 = t2.unique2;
QUERY PLAN
@ -197,30 +197,30 @@ regression-# AND t1.unique2 = t2.unique2;
-&gt; Index Scan using tenk2_unique2 on tenk2 t2
(cost=0.00..3.01 rows=1 width=148)
Index Cond: ("outer".unique2 = t2.unique2)
</programlisting>
</programlisting>
</para>
<para>
In this nested-loop join, the outer scan is the same index scan we had
in the example before last, and so its cost and row count are the same
because we are applying the <literal>unique1 &lt; 50</literal> WHERE clause at that node.
because we are applying the <literal>unique1 &lt; 50</literal> <literal>WHERE</> clause at that node.
The <literal>t1.unique2 = t2.unique2</literal> clause is not relevant yet, so it doesn't
affect row count of the outer scan. For the inner scan, the unique2 value of the
affect row count of the outer scan. For the inner scan, the <literal>unique2</> value of the
current
outer-scan tuple is plugged into the inner index scan
outer-scan row is plugged into the inner index scan
to produce an index condition like
<literal>t2.unique2 = <replaceable>constant</replaceable></literal>. So we get the
same inner-scan plan and costs that we'd get from, say, <literal>explain select
* from tenk2 where unique2 = 42</literal>. The costs of the loop node are then set
same inner-scan plan and costs that we'd get from, say, <literal>EXPLAIN SELECT
* FROM tenk2 WHERE unique2 = 42</literal>. The costs of the loop node are then set
on the basis of the cost of the outer scan, plus one repetition of the
inner scan for each outer tuple (49 * 3.01, here), plus a little CPU
inner scan for each outer row (49 * 3.01, here), plus a little CPU
time for join processing.
</para>
<para>
In this example the loop's output row count is the same as the product
of the two scans' row counts, but that's not true in general, because
in general you can have WHERE clauses that mention both relations and
in general you can have <literal>WHERE</> clauses that mention both relations and
so can only be applied at the join point, not to either input scan.
For example, if we added <literal>WHERE ... AND t1.hundred &lt; t2.hundred</literal>,
that would decrease the output row count of the join node, but not change
@ -233,9 +233,9 @@ regression-# AND t1.unique2 = t2.unique2;
flags for each plan type. (This is a crude tool, but useful. See
also <xref linkend="explicit-joins">.)
<programlisting>
regression=# set enable_nestloop = off;
SET VARIABLE
<programlisting>
regression=# SET enable_nestloop = off;
SET
regression=# EXPLAIN SELECT * FROM tenk1 t1, tenk2 t2 WHERE t1.unique1 &lt; 50
regression-# AND t1.unique2 = t2.unique2;
QUERY PLAN
@ -247,25 +247,25 @@ regression-# AND t1.unique2 = t2.unique2;
-&gt; Index Scan using tenk1_unique1 on tenk1 t1
(cost=0.00..179.33 rows=49 width=148)
Index Cond: (unique1 &lt; 50)
</programlisting>
</programlisting>
This plan proposes to extract the 50 interesting rows of <classname>tenk1</classname>
using ye same olde index scan, stash them into an in-memory hash table,
and then do a sequential scan of <classname>tenk2</classname>, probing into the hash table
for possible matches of <literal>t1.unique2 = t2.unique2</literal> at each <classname>tenk2</classname> tuple.
for possible matches of <literal>t1.unique2 = t2.unique2</literal> at each <classname>tenk2</classname> row.
The cost to read <classname>tenk1</classname> and set up the hash table is entirely start-up
cost for the hash join, since we won't get any tuples out until we can
cost for the hash join, since we won't get any rows out until we can
start reading <classname>tenk2</classname>. The total time estimate for the join also
includes a hefty charge for CPU time to probe the hash table
10000 times. Note, however, that we are NOT charging 10000 times 179.33;
includes a hefty charge for the CPU time to probe the hash table
10000 times. Note, however, that we are <emphasis>not</emphasis> charging 10000 times 179.33;
the hash table setup is only done once in this plan type.
</para>
<para>
It is possible to check on the accuracy of the planner's estimated costs
by using EXPLAIN ANALYZE. This command actually executes the query,
by using <command>EXPLAIN ANALYZE</>. This command actually executes the query,
and then displays the true run time accumulated within each plan node
along with the same estimated costs that a plain EXPLAIN shows.
along with the same estimated costs that a plain <command>EXPLAIN</command> shows.
For example, we might get a result like this:
<screen>
@ -296,7 +296,7 @@ regression-# WHERE t1.unique1 &lt; 50 AND t1.unique2 = t2.unique2;
<para>
In some query plans, it is possible for a subplan node to be executed more
than once. For example, the inner index scan is executed once per outer
tuple in the above nested-loop plan. In such cases, the
row in the above nested-loop plan. In such cases, the
<quote>loops</quote> value reports the
total number of executions of the node, and the actual time and rows
values shown are averages per-execution. This is done to make the numbers
@ -307,19 +307,19 @@ regression-# WHERE t1.unique1 &lt; 50 AND t1.unique2 = t2.unique2;
<para>
The <literal>Total runtime</literal> shown by <command>EXPLAIN ANALYZE</command> includes
executor start-up and shutdown time, as well as time spent processing
the result tuples. It does not include parsing, rewriting, or planning
time. For a SELECT query, the total run time will normally be just a
executor start-up and shut-down time, as well as time spent processing
the result rows. It does not include parsing, rewriting, or planning
time. For a <command>SELECT</> query, the total run time will normally be just a
little larger than the total time reported for the top-level plan node.
For INSERT, UPDATE, and DELETE queries, the total run time may be
For <command>INSERT</>, <command>UPDATE</>, and <command>DELETE</> commands, the total run time may be
considerably larger, because it includes the time spent processing the
result tuples. In these queries, the time for the top plan node
essentially is the time spent computing the new tuples and/or locating
result rows. In these commands, the time for the top plan node
essentially is the time spent computing the new rows and/or locating
the old ones, but it doesn't include the time spent making the changes.
</para>
<para>
It is worth noting that EXPLAIN results should not be extrapolated
It is worth noting that <command>EXPLAIN</> results should not be extrapolated
to situations other than the one you are actually testing; for example,
results on a toy-sized table can't be assumed to apply to large tables.
The planner's cost estimates are not linear and so it may well choose
@ -333,7 +333,7 @@ regression-# WHERE t1.unique1 &lt; 50 AND t1.unique2 = t2.unique2;
</sect1>
<sect1 id="planner-stats">
<title>Statistics used by the Planner</title>
<title>Statistics Used by the Planner</title>
<para>
As we saw in the previous section, the query planner needs to estimate
@ -351,8 +351,8 @@ regression-# WHERE t1.unique1 &lt; 50 AND t1.unique2 = t2.unique2;
with queries similar to this one:
<screen>
regression=# select relname, relkind, reltuples, relpages from pg_class
regression-# where relname like 'tenk1%';
regression=# SELECT relname, relkind, reltuples, relpages FROM pg_class
regression-# WHERE relname LIKE 'tenk1%';
relname | relkind | reltuples | relpages
---------------+---------+-----------+----------
tenk1 | r | 10000 | 233
@ -382,10 +382,10 @@ regression-# where relname like 'tenk1%';
<para>
Most queries retrieve only a fraction of the rows in a table, due
to having WHERE clauses that restrict the rows to be examined.
to having <literal>WHERE</> clauses that restrict the rows to be examined.
The planner thus needs to make an estimate of the
<firstterm>selectivity</> of WHERE clauses, that is, the fraction of
rows that match each clause of the WHERE condition. The information
<firstterm>selectivity</> of <literal>WHERE</> clauses, that is, the fraction of
rows that match each clause of the <literal>WHERE</> condition. The information
used for this task is stored in the <structname>pg_statistic</structname>
system catalog. Entries in <structname>pg_statistic</structname> are
updated by <command>ANALYZE</> and <command>VACUUM ANALYZE</> commands,
@ -406,7 +406,7 @@ regression-# where relname like 'tenk1%';
For example, we might do:
<screen>
regression=# select attname, n_distinct, most_common_vals from pg_stats where tablename = 'road';
regression=# SELECT attname, n_distinct, most_common_vals FROM pg_stats WHERE tablename = 'road';
attname | n_distinct | most_common_vals
---------+------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
name | -0.467008 | {"I- 580 Ramp","I- 880 Ramp","Sp Railroad ","I- 580 ","I- 680 Ramp","I- 80 Ramp","14th St ","5th St ","Mission Blvd","I- 880 "}
@ -414,12 +414,14 @@ regression=# select attname, n_distinct, most_common_vals from pg_stats where ta
(2 rows)
regression=#
</screen>
As of <productname>PostgreSQL</productname> 7.2 the following columns exist
in <structname>pg_stats</structname>:
</para>
<table>
<para>
<xref linkend="planner-pg-stats-table"> shows the columns that
exist in <structname>pg_stats</structname>.
</para>
<table id="planner-pg-stats-table">
<title><structname>pg_stats</structname> Columns</title>
<tgroup cols=3>
@ -435,7 +437,7 @@ regression=#
<row>
<entry><literal>tablename</literal></entry>
<entry><type>name</type></entry>
<entry>Name of table containing column</entry>
<entry>Name of the table containing the column</entry>
</row>
<row>
@ -447,13 +449,13 @@ regression=#
<row>
<entry><literal>null_frac</literal></entry>
<entry><type>real</type></entry>
<entry>Fraction of column's entries that are NULL</entry>
<entry>Fraction of column's entries that are null</entry>
</row>
<row>
<entry><literal>avg_width</literal></entry>
<entry><type>integer</type></entry>
<entry>Average width in bytes of column's entries</entry>
<entry>Average width in bytes of the column's entries</entry>
</row>
<row>
@ -462,7 +464,7 @@ regression=#
<entry>If greater than zero, the estimated number of distinct values
in the column. If less than zero, the negative of the number of
distinct values divided by the number of rows. (The negated form
is used when ANALYZE believes that the number of distinct values
is used when <command>ANALYZE</> believes that the number of distinct values
is likely to increase as the table grows; the positive form is used
when the column seems to have a fixed number of possible values.)
For example, -1 indicates a unique column in which the number of
@ -481,7 +483,7 @@ regression=#
<entry><literal>most_common_freqs</literal></entry>
<entry><type>real[]</type></entry>
<entry>A list of the frequencies of the most common values,
ie, number of occurrences of each divided by total number of rows.
i.e., number of occurrences of each divided by total number of rows.
</entry>
</row>
@ -530,30 +532,32 @@ regression=#
<title>Controlling the Planner with Explicit <literal>JOIN</> Clauses</title>
<para>
Beginning with <productname>PostgreSQL</productname> 7.1 it is possible
to control the query planner to some extent by using explicit <literal>JOIN</>
Beginning with <productname>PostgreSQL</productname> 7.1 it has been possible
to control the query planner to some extent by using the explicit <literal>JOIN</>
syntax. To see why this matters, we first need some background.
</para>
<para>
In a simple join query, such as
<programlisting>
SELECT * FROM a,b,c WHERE a.id = b.id AND b.ref = c.id;
</programlisting>
the planner is free to join the given tables in any order. For example,
it could generate a query plan that joins A to B, using the WHERE clause
a.id = b.id, and then joins C to this joined table, using the other
WHERE clause. Or it could join B to C and then join A to that result.
Or it could join A to C and then join them with B --- but that would
be inefficient, since the full Cartesian product of A and C would have
to be formed, there being no applicable WHERE clause to allow optimization
of the join.
(All joins in the <productname>PostgreSQL</productname> executor happen
between two input tables, so it's necessary to build up the result in one
or another of these fashions.) The important point is that these different
join possibilities give semantically equivalent results but may have hugely
different execution costs. Therefore, the planner will explore all of them
to try to find the most efficient query plan.
<programlisting>
SELECT * FROM a, b, c WHERE a.id = b.id AND b.ref = c.id;
</programlisting>
the planner is free to join the given tables in any order. For
example, it could generate a query plan that joins A to B, using
the <literal>WHERE</> condition <literal>a.id = b.id</>, and then
joins C to this joined table, using the other <literal>WHERE</>
condition. Or it could join B to C and then join A to that result.
Or it could join A to C and then join them with B --- but that
would be inefficient, since the full Cartesian product of A and C
would have to be formed, there being no applicable condition in the
<literal>WHERE</> clause to allow optimization of the join. (All
joins in the <productname>PostgreSQL</productname> executor happen
between two input tables, so it's necessary to build up the result
in one or another of these fashions.) The important point is that
these different join possibilities give semantically equivalent
results but may have hugely different execution costs. Therefore,
the planner will explore all of them to try to find the most
efficient query plan.
</para>
<para>
@ -567,7 +571,7 @@ SELECT * FROM a,b,c WHERE a.id = b.id AND b.ref = c.id;
search to a <firstterm>genetic</firstterm> probabilistic search
through a limited number of possibilities. (The switch-over threshold is
set by the <varname>GEQO_THRESHOLD</varname> run-time
parameter described in the <citetitle>Administrator's Guide</citetitle>.)
parameter described in the &cite-admin;.)
The genetic search takes less time, but it won't
necessarily find the best possible plan.
</para>
@ -575,9 +579,9 @@ SELECT * FROM a,b,c WHERE a.id = b.id AND b.ref = c.id;
<para>
When the query involves outer joins, the planner has much less freedom
than it does for plain (inner) joins. For example, consider
<programlisting>
<programlisting>
SELECT * FROM a LEFT JOIN (b JOIN c ON (b.ref = c.id)) ON (a.id = b.id);
</programlisting>
</programlisting>
Although this query's restrictions are superficially similar to the
previous example, the semantics are different because a row must be
emitted for each row of A that has no matching row in the join of B and C.
@ -587,27 +591,27 @@ SELECT * FROM a LEFT JOIN (b JOIN c ON (b.ref = c.id)) ON (a.id = b.id);
</para>
<para>
In <productname>PostgreSQL</productname> 7.1, the planner treats all
explicit JOIN syntaxes as constraining the join order, even though
The <productname>PostgreSQL</productname> query planner treats all
explicit <literal>JOIN</> syntaxes as constraining the join order, even though
it is not logically necessary to make such a constraint for inner
joins. Therefore, although all of these queries give the same result:
<programlisting>
SELECT * FROM a,b,c WHERE a.id = b.id AND b.ref = c.id;
<programlisting>
SELECT * FROM a, b, c WHERE a.id = b.id AND b.ref = c.id;
SELECT * FROM a CROSS JOIN b CROSS JOIN c WHERE a.id = b.id AND b.ref = c.id;
SELECT * FROM a JOIN (b JOIN c ON (b.ref = c.id)) ON (a.id = b.id);
</programlisting>
the second and third take less time to plan than the first. This effect
</programlisting>
but the second and third take less time to plan than the first. This effect
is not worth worrying about for only three tables, but it can be a
lifesaver with many tables.
</para>
<para>
You do not need to constrain the join order completely in order to
cut search time, because it's OK to use JOIN operators in a plain
FROM list. For example,
<programlisting>
cut search time, because it's OK to use <literal>JOIN</> operators in a plain
<literal>FROM</> list. For example,
<programlisting>
SELECT * FROM a CROSS JOIN b, c, d, e WHERE ...;
</programlisting>
</programlisting>
forces the planner to join A to B before joining them to other tables,
but doesn't constrain its choices otherwise. In this example, the
number of possible join orders is reduced by a factor of 5.
@ -617,22 +621,22 @@ SELECT * FROM a CROSS JOIN b, c, d, e WHERE ...;
If you have a mix of outer and inner joins in a complex query, you
might not want to constrain the planner's search for a good ordering
of inner joins inside an outer join. You can't do that directly in the
JOIN syntax, but you can get around the syntactic limitation by using
<literal>JOIN</> syntax, but you can get around the syntactic limitation by using
subselects. For example,
<programlisting>
<programlisting>
SELECT * FROM d LEFT JOIN
(SELECT * FROM a, b, c WHERE ...) AS ss
ON (...);
</programlisting>
</programlisting>
Here, joining D must be the last step in the query plan, but the
planner is free to consider various join orders for A,B,C.
planner is free to consider various join orders for A, B, C.
</para>
<para>
Constraining the planner's search in this way is a useful technique
both for reducing planning time and for directing the planner to a
good query plan. If the planner chooses a bad join order by default,
you can force it to choose a better order via JOIN syntax --- assuming
you can force it to choose a better order via <literal>JOIN</> syntax --- assuming
that you know of a better order, that is. Experimentation is recommended.
</para>
</sect1>
@ -658,6 +662,10 @@ SELECT * FROM d LEFT JOIN
If you allow each insertion to be committed separately,
<productname>PostgreSQL</productname> is doing a lot of work for each
record added.
An additional benefit of doing all insertions in one transaction
is that if the insertion of one record were to fail then the
insertion of all records inserted up to that point would be rolled
back, so you won't be stuck with partially loaded data.
</para>
</sect2>
@ -696,7 +704,7 @@ SELECT * FROM d LEFT JOIN
</sect2>
<sect2 id="populate-analyze">
<title>ANALYZE Afterwards</title>
<title>Run ANALYZE Afterwards</title>
<para>
It's a good idea to run <command>ANALYZE</command> or <command>VACUUM

20
doc/src/sgml/queries.sgml
View File

@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/queries.sgml,v 1.18 2002/10/20 05:05:46 tgl Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/queries.sgml,v 1.19 2002/11/11 20:14:03 petere Exp $ -->
<chapter id="queries">
<title>Queries</title>
@ -668,7 +668,7 @@ SELECT <replaceable>select_list</replaceable>
order in which the columns are listed does not matter. The
purpose is to reduce each group of rows sharing common values into
one group row that is representative of all rows in the group.
This is done to eliminate redundancy in the output and/or obtain
This is done to eliminate redundancy in the output and/or compute
aggregates that apply to these groups. For instance:
<screen>
<prompt>=></> <userinput>SELECT * FROM test1;</>
@ -694,7 +694,12 @@ SELECT <replaceable>select_list</replaceable>
In the second query, we could not have written <literal>SELECT *
FROM test1 GROUP BY x</literal>, because there is no single value
for the column <literal>y</> that could be associated with each
group. In general, if a table is grouped, columns that are not
group. The grouped-by columns can be referenced in the select list since
they have a known constant value per group.
</para>
<para>
In general, if a table is grouped, columns that are not
used in the grouping cannot be referenced except in aggregate
expressions. An example with aggregate expressions is:
<screen>
@ -712,11 +717,6 @@ SELECT <replaceable>select_list</replaceable>
linkend="functions-aggregate">.
</para>
<para>
The grouped-by columns can be referenced in the select list since
they have a known constant value per group.
</para>
<tip>
<para>
Grouping without aggregate expressions effectively calculates the
@ -740,7 +740,7 @@ SELECT product_id, p.name, (sum(s.units) * p.price) AS sales
in the <literal>GROUP BY</> clause since they are referenced in
the query select list. (Depending on how exactly the products
table is set up, name and price may be fully dependent on the
product ID, so the additional groups could theoretically be
product ID, so the additional groupings could theoretically be
unnecessary, but this is not implemented yet.) The column
<literal>s.units</> does not have to be in the <literal>GROUP
BY</> list since it is only used in an aggregate expression
@ -828,7 +828,7 @@ SELECT product_id, p.name, (sum(s.units) * (p.price - p.cost)) AS profit
</para>
<sect2 id="queries-select-list-items">
<title>Select List Items</title>
<title>Select-List Items</title>
<para>
The simplest kind of select list is <literal>*</literal> which

34
doc/src/sgml/query.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/query.sgml,v 1.27 2002/10/24 17:48:54 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/query.sgml,v 1.28 2002/11/11 20:14:03 petere Exp $
-->
<chapter id="tutorial-sql">
@ -13,7 +13,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/query.sgml,v 1.27 2002/10/24 17:48:54 peter
<acronym>SQL</acronym> to perform simple operations. This
tutorial is only intended to give you an introduction and is in no
way a complete tutorial on <acronym>SQL</acronym>. Numerous books
have been written on <acronym>SQL92</acronym>, including <xref
have been written on <acronym>SQL</acronym>, including <xref
linkend="MELT93"> and <xref linkend="DATE97">.
You should be aware that some <productname>PostgreSQL</productname>
language features are extensions to the standard.
@ -44,7 +44,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/query.sgml,v 1.27 2002/10/24 17:48:54 peter
The <literal>\i</literal> command reads in commands from the
specified file. The <literal>-s</literal> option puts you in
single step mode which pauses before sending each query to the
single step mode which pauses before sending each statement to the
server. The commands used in this section are in the file
<filename>basics.sql</filename>.
</para>
@ -502,7 +502,7 @@ SELECT *
join operator will have each of its rows in the output at least
once, whereas the table on the right will only have those rows
output that match some row of the left table. When outputting a
left-table row for which there is no right-table match, empty (NULL)
left-table row for which there is no right-table match, empty (null)
values are substituted for the right-table columns.
</para>
@ -601,7 +601,7 @@ SELECT max(temp_lo) FROM weather;
<para>
<indexterm><primary>subquery</primary></indexterm>
If we want to know what city (or cities) that reading occurred in,
If we wanted to know what city (or cities) that reading occurred in,
we might try
<programlisting>
@ -615,7 +615,7 @@ SELECT city FROM weather WHERE temp_lo = max(temp_lo); <lineannotation>WRONG
go into the aggregation stage; so it has to be evaluated before
aggregate functions are computed.)
However, as is often the case
the query can be restated to accomplish the intended result; here
the query can be restated to accomplish the intended result, here
by using a <firstterm>subquery</firstterm>:
<programlisting>
@ -630,9 +630,9 @@ SELECT city FROM weather
(1 row)
</screen>
This is OK because the sub-select is an independent computation
This is OK because the subquery is an independent computation
that computes its own aggregate separately from what is happening
in the outer select.
in the outer query.
</para>
<para>
@ -684,10 +684,18 @@ SELECT city, max(temp_lo)
<programlisting>
SELECT city, max(temp_lo)
FROM weather
WHERE city LIKE 'S%'
WHERE city LIKE 'S%'<co id="co.tutorial-agg-like">
GROUP BY city
HAVING max(temp_lo) < 40;
</programlisting>
<calloutlist>
<callout arearefs="co.tutorial-agg-like">
<para>
The <literal>LIKE</literal> operator does pattern matching and
is explained in the &cite-user;.
</para>
</callout>
</calloutlist>
</para>
<para>
@ -729,7 +737,7 @@ SELECT city, max(temp_lo)
You can update existing rows using the
<command>UPDATE</command> command.
Suppose you discover the temperature readings are
all off by 2 degrees as of November 28, you may update the
all off by 2 degrees as of November 28. You may update the
data as follows:
<programlisting>
@ -762,8 +770,8 @@ SELECT * FROM weather;
</indexterm>
<para>
Suppose you are no longer interested in the weather of Hayward,
then you can do the following to delete those rows from the table.
Suppose you are no longer interested in the weather of Hayward.
Then you can do the following to delete those rows from the table.
Deletions are performed using the <command>DELETE</command>
command:
<programlisting>
@ -786,7 +794,7 @@ SELECT * FROM weather;
</para>
<para>
One should be wary of queries of the form
One should be wary of statements of the form
<synopsis>
DELETE FROM <replaceable>tablename</replaceable>;
</synopsis>

482
doc/src/sgml/runtime.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.149 2002/11/08 17:37:52 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.150 2002/11/11 20:14:03 petere Exp $
-->
<Chapter Id="runtime">
@ -11,7 +11,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.149 2002/11/08 17:37:52 tg
</para>
<sect1 id="postgres-user">
<title>The <productname>PostgreSQL</productname> user account</title>
<title>The <productname>PostgreSQL</productname> User Account</title>
<indexterm>
<primary>postgres user</primary>
@ -37,7 +37,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.149 2002/11/08 17:37:52 tg
</sect1>
<sect1 id="creating-cluster">
<title>Creating a database cluster</title>
<title>Creating a Database Cluster</title>
<indexterm>
<primary>database cluster</primary>
@ -152,7 +152,7 @@ set to "C". For more information see the Administrator's Guide.
</screen>
This is intended to warn you that the currently selected locale
will cause indexes to be sorted in an order that prevents them from
being used for LIKE and regular-expression searches. If you need
being used for <literal>LIKE</> and regular-expression searches. If you need
good performance in such searches, you should set your current
locale to <literal>C</> and re-run <command>initdb</command>, e.g.,
by running <literal>initdb --lc-collate=C</literal>. The sort
@ -165,7 +165,7 @@ set to "C". For more information see the Administrator's Guide.
</sect1>
<sect1 id="postmaster-start">
<title>Starting the database server</title>
<title>Starting the Database Server</title>
<para>
<indexterm>
@ -229,7 +229,7 @@ pg_ctl start -l logfile
<para>
Normally, you will want to start the database server when the
computer boots. Auto-start scripts are operating-system specific.
computer boots. Autostart scripts are operating system-specific.
There are a few distributed with
<productname>PostgreSQL</productname> in the
<filename>/contrib/start-scripts</> directory. This may require root
@ -384,13 +384,13 @@ IpcSemaphoreCreate: semget(key=5440026, num=16, 01600) failed: No space left on
means your kernel's limit on the number of System V semaphores is
smaller than the number <productname>PostgreSQL</productname> wants
to create. As above, you may be able to work around the problem by
starting the postmaster with a reduced number of backend processes
starting the postmaster with a reduced number of allowed connections
(<option>-N</option> switch), but you'll eventually want to
increase the kernel limit.
</para>
<para>
If you get an <quote>illegal system call</> error, it is likely
If you get an <quote>illegal system call</> error, it is likely that
shared memory or semaphores are not supported in your kernel at
all. In that case your only option is to reconfigure the kernel to
enable these features.
@ -456,7 +456,7 @@ psql: could not connect to server: Connection refused
</sect1>
<sect1 id="runtime-config">
<Title>Run-time configuration</Title>
<Title>Run-time Configuration</Title>
<indexterm>
<primary>configuration</primary>
@ -558,7 +558,7 @@ env PGOPTIONS='-c geqo=off' psql
<title>pg_settings</title>
<para>
<structname>pg_settings</structname> virtual table allows display and update
The <structname>pg_settings</structname> virtual table allows display and update
of current session run-time parameters. There is one entry for each of the
available parameters provided by <command>SHOW ALL</command>. But it is
in a form that allows it to be joined with other relations and have a
@ -579,28 +579,25 @@ env PGOPTIONS='-c geqo=off' psql
<table>
<title>pg_settings Columns</title>
<tgroup cols=4>
<tgroup cols=3>
<thead>
<row>
<entry>Name</entry>
<entry>Type</entry>
<entry>References</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>name</entry>
<entry><literal>name</literal></entry>
<entry><type>text</type></entry>
<entry></entry>
<entry>The name of a current session run-time parameter</entry>
</row>
<row>
<entry>setting</entry>
<entry><literal>setting</literal></entry>
<entry><type>text</type></entry>
<entry></entry>
<entry>The value of a current session run-time parameter</entry>
</row>
</tbody>
@ -630,7 +627,7 @@ env PGOPTIONS='-c geqo=off' psql
<listitem>
<para>
Sets the optimizer's estimate of the cost of processing each
operator in a WHERE clause. This is measured as a fraction of
operator in a <literal>WHERE</> clause. This is measured as a fraction of
the cost of a sequential page fetch.
</para>
</listitem>
@ -860,85 +857,93 @@ env PGOPTIONS='-c geqo=off' psql
<term><varname>SERVER_MIN_MESSAGES</varname> (<type>string</type>)</term>
<listitem>
<para>
This controls how much detail is written to the server logs. The
default is <literal>NOTICE</>. Valid values are <literal>DEBUG5</>,
This controls how much message detail is written to the server
logs. 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</>. Later values send less
detail to the logs. <literal>LOG</> has a different precedence
here than in <literal>CLIENT_MIN_MESSAGES</>.
<literal>WARNING</>, <literal>ERROR</>, <literal>LOG</>,
<literal>FATAL</>, and <literal>PANIC</>. Later values send
less detail to the logs. The default is <literal>NOTICE</>.
Note that <literal>LOG</> has a different precedence here than
in <literal>CLIENT_MIN_MESSAGES</>.
</para>
<para>
Here is a summary of the various message types:
<variablelist>
<varlistentry>
<term><varname>DEBUG[1-5]</varname></term>
<term><literal>DEBUG[1-5]</literal></term>
<listitem>
<para>
This provides information for use by developers.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>INFO</varname></term>
<listitem>
<para>
This provides information requested by the user, e.g.
<command>SET</>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>NOTICE</varname></term>
<listitem>
<para>
This provides information that may be helpful to users, e.g.
truncation of long identifiers, sequence creation as part of
<command>SERIAL</>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>WARNING</varname></term>
<listitem>
<para>
This provides warnings to the user, e.g. <command>COMMIT</>
outside a transaction.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ERROR</varname></term>
<listitem>
<para>
Reports the error that caused the transaction to abort.
Provides information for use by developers.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>LOG</varname></term>
<term><literal>INFO</literal></term>
<listitem>
<para>
This reports information of interest to administrators, e.g.
Provides information implicitly requested by the user,
e.g., during <command>VACUUM VERBOSE</>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>NOTICE</literal></term>
<listitem>
<para>
Provides information that may be helpful to users, e.g.,
truncation of long identifiers and index creation as part
of primary keys.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>WARNING</literal></term>
<listitem>
<para>
Provides warnings to the user, e.g., <command>COMMIT</>
outside a transaction.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>ERROR</literal></term>
<listitem>
<para>
Reports the error that caused a transaction to abort.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>LOG</literal></term>
<listitem>
<para>
Reports information of interest to administrators, e.g.,
checkpoint activity.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>FATAL</varname></term>
<term><literal>FATAL</literal></term>
<listitem>
<para>
This reports why the backend session terminated.
Reports why a backend session terminated.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>PANIC</varname></term>
<term><literal>PANIC</literal></term>
<listitem>
<para>
This reports why all backends restarted.
Reports why all backend sessions restarted.
</para>
</listitem>
</varlistentry>
@ -951,15 +956,15 @@ env PGOPTIONS='-c geqo=off' psql
<term><varname>CLIENT_MIN_MESSAGES</varname> (<type>string</type>)</term>
<listitem>
<para>
This controls how much detail is written to the client. The
default is <literal>NOTICE</>. Valid values are
<literal>DEBUG5</>, <literal>DEBUG4</>, <literal>DEBUG3</>,
<literal>DEBUG2</>, <literal>DEBUG1</>, <literal>LOG</>,
<literal>NOTICE</>, <literal>WARNING</>, and <literal>ERROR</>.
Later values send less information to the user. <literal>LOG</>
has a different precedence here than in
<literal>SERVER_MIN_MESSAGES</>. Also see that section for an
explanation of the various values.
This controls how much message detail is written to the
client. Valid values are <literal>DEBUG5</>,
<literal>DEBUG4</>, <literal>DEBUG3</>, <literal>DEBUG2</>,
<literal>DEBUG1</>, <literal>LOG</>, <literal>NOTICE</>,
<literal>WARNING</>, and <literal>ERROR</>. Later values send
less information to the client. The default is
<literal>NOTICE</>. Note that <literal>LOG</> has a different
precedence here than in <literal>SERVER_MIN_MESSAGES</>. Also
see that section for an explanation of the various values.
</para>
</listitem>
</varlistentry>
@ -973,7 +978,7 @@ env PGOPTIONS='-c geqo=off' psql
to turn this on, as it might expose programming mistakes. To use
this option, the macro <literal>USE_ASSERT_CHECKING</literal>
must be defined when <productname>PostgreSQL</productname> is
built (accomplished by the configure option
built (accomplished by the <command>configure</command> option
<option>--enable-cassert</option>). Note that
<literal>DEBUG_ASSERTIONS</literal> defaults to on if
<productname>PostgreSQL</productname> has been built with
@ -990,7 +995,7 @@ env PGOPTIONS='-c geqo=off' psql
<listitem>
<para>
These flags enable various debugging output to be sent to the
server log. For each executed query, prints either the query text,
server log. For each executed query, print either the query text,
the resulting parse tree, the query rewriter output, or the execution
plan. <option>DEBUG_PRETTY_PRINT</option> indents these displays
to produce a more readable but much longer output format.
@ -1032,22 +1037,39 @@ env PGOPTIONS='-c geqo=off' psql
</listitem>
</varlistentry>
<varlistentry>
<term><varname>LOG_DURATION</varname> (<type>boolean</type>)</term>
<listitem>
<para>
Causes the duration of every completed statement to be logged.
To use this option, enable <varname>LOG_STATEMENT</> and
<varname>LOG_PID</> so you can link the statement to the
duration using the process ID.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>LOG_MIN_ERROR_STATEMENT</varname> (<type>string</type>)</term>
<listitem>
<para>
This controls which message types output the original query to
the server logs. All queries matching the setting or higher are
logged. The default is <literal>PANIC</literal> (effectively
"off"). 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>FATAL</literal>, and <literal>PANIC</literal>.
This controls for which message levels the SQL statement
causing that message is to be recorded in the server log. All
statements causing a message of the level of the setting or
higher are logged. The default is <literal>PANIC</literal>
(effectively turning this feature off). 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>FATAL</literal>, and
<literal>PANIC</literal>. For example, if you set this to
<literal>ERROR</literal> then all SQL statements causing
errors, fatal errors, or panics will be logged.
</para>
<para>
It is recommended you enable <literal>LOG_PID</literal> as well
It is recommended you enable <varname>LOG_PID</varname> as well
so you can more easily match the error statement with the error
message.
</para>
@ -1071,18 +1093,7 @@ env PGOPTIONS='-c geqo=off' psql
<term><varname>LOG_STATEMENT</varname> (<type>boolean</type>)</term>
<listitem>
<para>
Prints each query received.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>LOG_DURATION</varname> (<type>boolean</type>)</term>
<listitem>
<para>
Prints the duration of every completed query. To use this option,
enable <literal>LOG_STATEMENT</> and <literal>LOG_PID</> so you
can link the original query to the duration using the process id.
Causes each SQL statement to be logged.
</para>
</listitem>
</varlistentry>
@ -1186,9 +1197,12 @@ env PGOPTIONS='-c geqo=off' psql
This option determines the <application>syslog</application>
<quote>facility</quote> to be used when
<application>syslog</application> is enabled. You may choose
from LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6,
LOCAL7; the default is LOCAL0. See also the documentation of
your system's <application>syslog</application>.
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>.
</para>
</listitem>
</varlistentry>
@ -1221,12 +1235,12 @@ env PGOPTIONS='-c geqo=off' psql
</sect2>
<sect2 id="runtime-config-general">
<title>General operation</title>
<title>General Operation</title>
<para>
<variablelist>
<varlistentry>
<term><varname>AUTOCOMMIT</varname> (<type>bool</type>)</term>
<term><varname>AUTOCOMMIT</varname> (<type>boolean</type>)</term>
<indexterm><primary>autocommit</></>
<listitem>
<para>
@ -1254,7 +1268,7 @@ env PGOPTIONS='-c geqo=off' psql
Once another command is issued, a transaction block
begins and any <command>SET</>, <command>SHOW</>, or
<command>RESET</> commands are considered to be part of the
transaction, i.e. they are committed or rolled back depending
transaction, i.e., they are committed or rolled back depending
on the completion status of the transaction. To execute a
<command>SET</>, <command>SHOW</>, or <command>RESET</>
command at the start of a transaction block, use <command>BEGIN</>
@ -1276,7 +1290,7 @@ env PGOPTIONS='-c geqo=off' psql
</varlistentry>
<varlistentry>
<term><varname>AUSTRALIAN_TIMEZONES</varname> (<type>bool</type>)</term>
<term><varname>AUSTRALIAN_TIMEZONES</varname> (<type>boolean</type>)</term>
<indexterm><primary>Australian time zones</></>
<listitem>
<para>
@ -1330,19 +1344,33 @@ env PGOPTIONS='-c geqo=off' psql
<term><varname>DB_USER_NAMESPACE</varname> (<type>boolean</type>)</term>
<listitem>
<para>
This allows per-database user names. You can create users as <literal>
username@dbname</>. When <literal>username</> is passed by the client,
<literal>@</> and the database name is appended to the user name and
that database-specific user name is looked up by the server.
When creating user names containing <literal>@</>, you will need
to quote the user name.
This allows per-database user names. It is off by default.
</para>
<para>
With this option 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 and looked up
by the server.
If this is on, create users as <literal> username@dbname</>.
When <literal>username</> is passed by a connecting client,
<literal>@</> and the database name is 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 option 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>
@ -1393,7 +1421,7 @@ env PGOPTIONS='-c geqo=off' psql
</para>
<para>
Consult the <citetitle>PostgreSQL User's Guide</citetitle> and
Consult the &cite-user; and
the command <command>SET TRANSACTION</command> for more
information.
</para>
@ -1424,11 +1452,9 @@ env PGOPTIONS='-c geqo=off' psql
distribution are installed. (Use <literal>pg_config
--pkglibdir</literal> to print the name of this directory.) For
example:
<informalexample>
<programlisting>
dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
</programlisting>
</informalexample>
</para>
<para>
@ -1690,8 +1716,8 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
<listitem>
<para>
When a password is specified in <command>CREATE USER</> or
<command>ALTER USER</> without writing either ENCRYPTED or
UNENCRYPTED, this flag determines whether the password is to be
<command>ALTER USER</> without writing either <literal>ENCRYPTED</> or
<literal>UNENCRYPTED</>, this flag determines whether the password is to be
encrypted. The default is on (encrypt the password).
</para>
</listitem>
@ -1714,37 +1740,37 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
<indexterm><primary>namespaces</></>
<listitem>
<para>
This variable specifies the order in which namespaces are searched
when an object (table, data type, function, etc) is referenced by a
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 namespaces, the one found first
identical names in different schemas, the one found first
in the search path is used. An object that is not in any of the
namespaces in the search path can only be referenced by specifying
its containing namespace with a qualified (dotted) name.
schemas in the search path can only be referenced by specifying
its containing schema with a qualified (dotted) name.
</para>
<para>
The value for search_path has to be a comma-separated
list of namespace (schema) names. If one of the list items is
the special value <literal>$user</literal>, then the namespace
having the same name as the SESSION_USER is substituted, if there
is such a namespace. (If not, <literal>$user</literal> is ignored.)
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>$user</literal>, then the schema
having the same name as the <function>SESSION_USER</> is substituted, if there
is such a schema. (If not, <literal>$user</literal> is ignored.)
</para>
<para>
The system catalog namespace, <literal>pg_catalog</>, is always
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.
It should also be noted that the temporary-table namespace,
<literal>pg_temp_nnn</>, is implicitly searched before any of
It should also be noted that the temporary-table schema,
<literal>pg_temp_<replaceable>nnn</></>, is implicitly searched before any of
these.
</para>
<para>
When objects are created without specifying a particular target
namespace, they will be placed in the first namespace listed
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>
@ -1752,21 +1778,14 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
<para>
The default value for this parameter is
<literal>'$user, public'</literal> (where the second part will be
ignored if there is no namespace named <literal>public</>).
ignored if there is no schema named <literal>public</>).
This supports shared use of a database (where no users
have private namespaces, and all share use of <literal>public</>),
private per-user namespaces, and combinations of these. Other
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>
By default, a newly created database will contain a world-writable
namespace named <literal>public</>, but no private namespaces.
The administrator may choose to restrict permissions on
<literal>public</> or even remove it, if that suits his purposes.
</para>
<para>
<indexterm>
<primary>schemas</primary>
@ -1779,6 +1798,10 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
shows how the requests appearing in <varname>search_path</varname>
were resolved.
</para>
<para>
For more information on schema handling, see the &cite-user;.
</para>
</listitem>
</varlistentry>
@ -1807,10 +1830,10 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
<term><varname>SILENT_MODE</varname> (<type>bool</type>)</term>
<listitem>
<para>
Runs postmaster silently. If this option is set, the postmaster
Runs the server silently. If this option is set, the server
will automatically run in background and any controlling ttys
are disassociated, thus no messages are written to standard
output or standard error (same effect as postmaster's -S
output or standard error (same effect as <command>postmaster</>'s <option>-S</option>
option). Unless some logging system such as
<application>syslog</> is enabled, using this option is
discouraged since it makes it impossible to see error messages.
@ -1824,14 +1847,14 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
<para>
Specifies the amount of memory to be used by internal sorts and
hashes before switching to temporary disk files. The value is
specified in kilobytes, and defaults to 1024 kilobytes (1MB).
specified in kilobytes, and defaults to 1024 kilobytes (1 MB).
Note that for a complex query, several sorts might be running in
parallel, and each one will be allowed to use as much memory as
this value specifies before it starts to put data into temporary
files. Also, each running backend could be doing one or more
sorts simultaneously, so the total memory used could be many
times the value of <varname>SORT_MEM</varname>. Sorts are used
by ORDER BY, merge joins, and CREATE INDEX.
by <literal>ORDER BY</>, merge joins, and <command>CREATE INDEX</>.
</para>
</listitem>
</varlistentry>
@ -1847,8 +1870,7 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
behavior you can set this variable to off, but in the long run
you are encouraged to change your applications to use the
<literal>ONLY</literal> keyword to exclude subtables. See the
SQL language reference and the <citetitle>User's
Guide</citetitle> for more information about inheritance.
SQL language reference and the &cite-user; for more information about inheritance.
</para>
</listitem>
</varlistentry>
@ -1887,7 +1909,7 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
<para>
Sets the time zone for displaying and interpreting timestamps.
The default is to use whatever the system environment
specifies as the timezone.
specifies as the time zone.
</para>
</listitem>
</varlistentry>
@ -1901,10 +1923,10 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
<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,
return true if <replaceable>expr</> evaluates to the null value,
and false otherwise. The correct behavior of
<literal><replaceable>expr</> = NULL</literal> is to always
return NULL (unknown). Therefore this option defaults to off.
return null (unknown). Therefore this option defaults to off.
</para>
<para>
@ -1914,11 +1936,11 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
null values, so if you use that interface to access the database you
might want to turn this option on. Since expressions of the
form <literal><replaceable>expr</> = NULL</literal> always
return NULL (using the correct interpretation) they are not
return the null value (using the correct interpretation) they are not
very useful and do not appear often in normal applications, so
this option does little harm in practice. But new users are
frequently confused about the semantics of expressions
involving NULL, so this option is not on by default.
involving null values, so this option is not on by default.
</para>
<para>
@ -1930,8 +1952,7 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
</para>
<para>
Refer to the <citetitle>User's Guide</citetitle> for related
information.
Refer to the &cite-user; for related information.
</para>
</listitem>
</varlistentry>
@ -1941,7 +1962,7 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
<listitem>
<para>
Specifies the directory of the Unix-domain socket on which the
<application>postmaster</application> is to listen for
server is to listen for
connections from client applications. The default is normally
<filename>/tmp</filename>, but can be changed at build time.
</para>
@ -1954,7 +1975,7 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
<para>
Sets the group owner of the Unix domain socket. (The owning
user of the socket is always the user that starts the
postmaster.) In combination with the option
server.) In combination with the option
<option>UNIX_SOCKET_PERMISSIONS</option> this can be used as
an additional access control mechanism for this socket type.
By default this is the empty string, which uses the default
@ -1982,7 +2003,7 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
anyone can connect. Reasonable alternatives are
<literal>0770</literal> (only user and group, see also under
<option>UNIX_SOCKET_GROUP</option>) and <literal>0700</literal>
(only user). (Note that actually for a Unix socket, only write
(only user). (Note that actually for a Unix domain socket, only write
permission matters and there is no point in setting or revoking
read or execute permissions.)
</para>
@ -2070,8 +2091,8 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
enough additional transactions may 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 COMMIT_SIBLINGS other transactions
are active at the instant that a backend has written its commit
only performed if at least <varname>COMMIT_SIBLINGS</varname> other transactions
are active at the instant that a backend process has written its commit
record.
</para>
</listitem>
@ -2103,7 +2124,7 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
<term><varname>WAL_DEBUG</varname> (<type>integer</type>)</term>
<listitem>
<para>
If non-zero, turn on WAL-related debugging output on standard
If nonzero, turn on WAL-related debugging output on standard
error.
</para>
</listitem>
@ -2130,107 +2151,111 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
</sect2>
<sect2 id="runtime-config-short">
<title>Short options</title>
<sect2 id="runtime-config-short">
<title>Short Options</title>
<para>
For convenience there are also single letter option switches
available for many parameters. They are described in the following
table.
available for many parameters. They are described in <xref
linkend="runtime-config-short-table">.
</para>
<table>
<table id="runtime-config-short-table">
<title>Short option key</title>
<tgroup cols="3">
<colspec colnum="3" align="center">
<tgroup cols="2">
<thead>
<row>
<entry>Short option</entry>
<entry>Equivalent</entry>
<entry>Remark</entry>
</row>
</thead>
<tbody>
<row>
<entry><option>-B <replaceable>x</replaceable></option></entry>
<entry><literal>shared_buffers = <replaceable>x</replaceable></></entry>
<entry></entry>
</row>
<row>
<entry><option>-d <replaceable>x</replaceable></option></entry>
<entry><literal>server_min_messages = <replaceable>DEBUGx</replaceable></></entry>
<entry></entry>
<entry><literal>server_min_messages = DEBUG<replaceable>x</replaceable></></entry>
</row>
<row>
<entry><option>-F</option></entry>
<entry><literal>fsync = off</></entry>
<entry></entry>
</row>
<row>
<entry><option>-h <replaceable>x</replaceable></option></entry>
<entry><literal>virtual_host = <replaceable>x</replaceable></></entry>
<entry></entry>
</row>
<row>
<entry><option>-i</option></entry>
<entry><literal>tcpip_socket = on</></entry>
<entry></entry>
</row>
<row>
<entry><option>-k <replaceable>x</replaceable></option></entry>
<entry><literal>unix_socket_directory = <replaceable>x</replaceable></></entry>
<entry></entry>
</row>
<row>
<entry><option>-l</option></entry>
<entry><literal>ssl = on</></entry>
<entry></entry>
</row>
<row>
<entry><option>-N <replaceable>x</replaceable></option></entry>
<entry><literal>max_connections = <replaceable>x</replaceable></></entry>
<entry></entry>
</row>
<row>
<entry><option>-p <replaceable>x</replaceable></option></entry>
<entry><literal>port = <replaceable>x</replaceable></></entry>
<entry></entry>
</row>
<row>
<entry><option>-fi</option>, <option>-fh</option>, <option>-fm</option>, <option>-fn</option>, <option>-fs</option>, <option>-ft</option></entry>
<entry><literal>enable_indexscan=off</>, <literal>enable_hashjoin=off</>,
<literal>enable_mergejoin=off</>, <literal>enable_nestloop=off</>, <literal>enable_seqscan=off</>,
<literal>enable_tidscan=off</></entry>
<entry>*</entry>
<entry>
<option>-fi</option>, <option>-fh</option>,
<option>-fm</option>, <option>-fn</option>,
<option>-fs</option>, <option>-ft</option><footnote
id="fn.runtime-config-short">
<para>
For historical reasons, these options must be passed to
the individual backend process via the <option>-o</option>
postmaster option, for example,
<screen>
$ <userinput>postmaster -o '-S 1024 -s'</userinput>
</screen>
or via <envar>PGOPTIONS</envar> from the client side, as
explained above.
</para>
</footnote>
</entry>
<entry>
<literal>enable_indexscan=off</>,
<literal>enable_hashjoin=off</>,
<literal>enable_mergejoin=off</>,
<literal>enable_nestloop=off</>,
<literal>enable_seqscan=off</>,
<literal>enable_tidscan=off</>
</entry>
</row>
<row>
<entry><option>-S <replaceable>x</replaceable></option></entry>
<entry><literal>sort_mem = <replaceable>x</replaceable></></entry>
<entry>*</entry>
</row>
<row>
<entry><option>-s</option></entry>
<entry><option>-s</option><footnoteref linkend="fn.runtime-config-short"></entry>
<entry><literal>show_statement_stats = on</></entry>
<entry>*</entry>
</row>
<row>
<entry><option>-tpa</option>, <option>-tpl</option>, <option>-te</option></entry>
<entry><option>-S <replaceable>x</replaceable></option><footnoteref linkend="fn.runtime-config-short">
</entry>
<entry><literal>sort_mem = <replaceable>x</replaceable></></entry>
</row>
<row>
<entry><option>-tpa</option>, <option>-tpl</option>, <option>-te</option><footnoteref linkend="fn.runtime-config-short"></entry>
<entry><literal>show_parser_stats=on</>, <literal>show_planner_stats=on</>, <literal>show_executor_stats=on</></entry>
<entry>*</entry>
</row>
</tbody>
</tgroup>
</table>
For historical reasons, options marked <quote>*</quote> must be
passed to the individual backend process via the
<option>-o</option> postmaster option, for example,
<screen>
$ <userinput>postmaster -o '-S 1024 -s'</userinput>
</screen>
or via <envar>PGOPTIONS</envar> from the client side, as explained
above.
</para>
</sect2>
</sect2>
</sect1>
@ -2305,7 +2330,7 @@ $ <userinput>postmaster -o '-S 1024 -s'</userinput>
<row>
<entry><varname>SHMMAX</></>
<entry>Maximum size of shared memory segment (bytes)</>
<entry>250kB + 8.2kB * <varname>shared_buffers</> + 14.2kB * <varname>max_connections</> or infinity</entry>
<entry>250kB + 8.2 kB * <varname>shared_buffers</> + 14.2 kB * <varname>max_connections</> or infinity</entry>
</row>
<row>
@ -2453,7 +2478,7 @@ $ <userinput>postmaster -o '-S 1024 -s'</userinput>
mind that shared memory is not pageable; it is locked in RAM.
To increase the number of shared buffers supported by the
postmaster, add the following to your kernel configuration
file. A <varname>SHMALL</> value of 1024 represents 4MB of
file. A <varname>SHMALL</> value of 1024 represents 4 MB of
shared memory. The following increases the maximum shared
memory area to 32 MB:
<programlisting>
@ -2466,7 +2491,7 @@ options "SHMMAX=\(SHMALL*PAGE_SIZE\)"
<para>
For those running 4.1 or later, just make the above changes,
recompile the kernel, and reboot. For those running earlier
releases, use <application>bpatch</> to find the
releases, use <command>bpatch</> to find the
<varname>sysptsize</> value in the current kernel. This is
computed dynamically at boot time.
<screen>
@ -2812,7 +2837,7 @@ default:\
<sect1 id="postmaster-shutdown">
<title>Shutting down the server</title>
<title>Shutting Down the Server</title>
<para>
There are several ways to shut down the database server. You control
@ -2903,14 +2928,16 @@ $ <userinput>kill -INT `head -1 /usr/local/pgsql/data/postmaster.pid`</userinput
<para>
With SSL support compiled in, the <productname>PostgreSQL</> server
can be started with the argument <option>-l</> (ell) to enable
SSL connections. When starting in SSL mode, the server will look
for the files <filename>server.key</> and <filename>server.crt</> in
the data directory. These files should contain the server private key
and certificate respectively. These files must be set up correctly
before an SSL-enabled server can start. If the private key is protected
with a passphrase, the server will prompt for the passphrase and will
not start until it has been entered.
can be started with SSL support by setting the parameter
<varname>ssl</varname> to on in
<filename>postgresql.conf</filename>. When starting in SSL mode,
the server will look for the files <filename>server.key</> and
<filename>server.crt</> in the data directory. These files should
contain the server private key and certificate respectively. These
files must be set up correctly before an SSL-enabled server can
start. If the private key is protected with a passphrase, the
server will prompt for the passphrase and will not start until it
has been entered.
</para>
<para>
@ -2924,19 +2951,18 @@ $ <userinput>kill -INT `head -1 /usr/local/pgsql/data/postmaster.pid`</userinput
For details on how to create your server private key and certificate,
refer to the <productname>OpenSSL</> documentation. A simple
self-signed certificate can be used to get started for testing, but a
certificate signed by a <acronym>CA</> (either one of the global
certificate signed by a certificate authority (<acronym>CA</>) (either one of the global
<acronym>CAs</> or a local one) should be used in production so the
client can verify the server's identity. To create a quick
self-signed certificate, use the following
<productname>OpenSSL</productname> command:
<programlisting>
cd <replaceable>$PGDATA</replaceable>
openssl req -new -text -out server.req
</programlisting>
Fill out the information that <command>openssl</> asks for. Make sure
that you enter the local host name as Common Name; the challenge
password can be left blank. The script will generate a key that is
passphrase protected; it will not accept a pass phrase that is less
passphrase protected; it will not accept a passphrase that is less
than four characters long. To remove the passphrase (as you must if
you want automatic start-up of the server), run the commands
<programlisting>
@ -2954,7 +2980,7 @@ chmod og-rwx server.key
</sect1>
<sect1 id="ssh-tunnels">
<title>Secure TCP/IP Connections with <application>SSH</application> tunnels</title>
<title>Secure TCP/IP Connections with <application>SSH</application> Tunnels</title>
<indexterm zone="ssh-tunnels">
<primary>ssh</primary>
@ -2970,20 +2996,20 @@ chmod og-rwx server.key
</note>
<para>
One can use <productname>ssh</productname> to encrypt the network
One can use <application>SSH</application> to encrypt the network
connection between clients and a
<productname>PostgreSQL</productname> server. Done properly, this
should lead to an adequately secure network connection.
provides an adequately secure network connection.
</para>
<para>
First make sure that an <application>ssh</application> server is
First make sure that an <application>SSH</application> server is
running properly on the same machine as
<productname>PostgreSQL</productname> and that you can log in using
<command>ssh</command> as some user. Then you can establish a secure
tunnel with a command like this from the client machine:
<programlisting>
$ <userinput>ssh -L 3333:foo.com:5432 joe@foo.com</userinput>
ssh -L 3333:foo.com:5432 joe@foo.com
</programlisting>
The first number in the <option>-L</option> argument, 3333, is the
port number of your end of the tunnel; it can be chosen freely. The
@ -3006,7 +3032,7 @@ psql -h localhost -p 3333 template1
<tip>
<para>
Several other products exist that can provide secure tunnels using
Several other applications exist that can provide secure tunnels using
a procedure similar in concept to the one just described.
</para>
</tip>

10
doc/src/sgml/start.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/start.sgml,v 1.26 2002/10/24 17:48:54 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/start.sgml,v 1.27 2002/11/11 20:14:04 petere Exp $
-->
<chapter id="tutorial-start">
@ -281,10 +281,10 @@ createdb: database creation failed
<listitem>
<para>
Using an existing graphical frontend tool like
<application>PgAccess</application> or
<application>ApplixWare</application> (via
<acronym>ODBC</acronym>) to create and manipulate a database.
These possibilities are not covered in this tutorial.
<application>PgAccess</application> or an office suite with
<acronym>ODBC</acronym> support to create and manipulate a
database. These possibilities are not covered in this
tutorial.
</para>
</listitem>

117
doc/src/sgml/syntax.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.72 2002/10/24 17:48:54 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.73 2002/11/11 20:14:04 petere Exp $
-->
<chapter id="sql-syntax">
@ -121,7 +121,7 @@ INSERT INTO MY_TABLE VALUES (3, 'hi there');
characters of an identifier; longer names can be written in
commands, but they will be truncated. By default,
<symbol>NAMEDATALEN</symbol> is 64 so the maximum identifier length
is 63 (but at the time the system is built,
is 63 (but at the time PostgreSQL is built,
<symbol>NAMEDATALEN</symbol> can be changed in
<filename>src/include/postgres_ext.h</filename>).
</para>
@ -170,8 +170,9 @@ UPDATE "my_table" SET "a" = 5;
<para>
Quoted identifiers can contain any character other than a double
quote itself. This allows constructing table or column names that
would otherwise not be possible, such as ones containing spaces or
quote itself. To include a double quote, write two double quotes.
This allows constructing table or column names that would
otherwise not be possible, such as ones containing spaces or
ampersands. The length limitation still applies.
</para>
@ -272,7 +273,7 @@ SELECT 'foobar';
SELECT 'foo' 'bar';
</programlisting>
is not valid syntax. (This slightly bizarre behavior is specified
by <acronym>SQL9x</acronym>; <productname>PostgreSQL</productname> is
by <acronym>SQL</acronym>; <productname>PostgreSQL</productname> is
following the standard.)
</para>
</sect3>
@ -298,7 +299,7 @@ SELECT 'foo' 'bar';
Alternatively, bit-string constants can be specified in hexadecimal
notation, using a leading <literal>X</literal> (upper or lower case),
e.g., <literal>X'1FF'</literal>. This notation is equivalent to
a bit-string constant with four binary digits for each hex digit.
a bit-string constant with four binary digits for each hexadecimal digit.
</para>
<para>
@ -328,7 +329,7 @@ SELECT 'foo' 'bar';
decimal point, if one is used. At least one digit must follow the
exponent marker (<literal>e</literal>), if one is present.
There may not be any spaces or other characters embedded in the
constant. Notice that any leading plus or minus sign is not actually
constant. Note that any leading plus or minus sign is not actually
considered part of the constant; it is an operator applied to the
constant.
</para>
@ -650,13 +651,16 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> )
</indexterm>
<para>
The precedence and associativity of the operators is hard-wired
into the parser. Most operators have the same precedence and are
left-associative. This may lead to non-intuitive behavior; for
example the Boolean operators <literal>&lt;</> and <literal>&gt;</> have a different
precedence than the Boolean operators <literal>&lt;=</> and <literal>&gt;=</>. Also,
you will sometimes need to add parentheses when using combinations
of binary and unary operators. For instance
<xref linkend="sql-precedence-table"> shows the precedence and
associativity of the operators in PostgreSQL. Most operators have
the same precedence and are left-associative. The precedence and
associativity of the operators is hard-wired into the parser.
This may lead to non-intuitive behavior; for example the Boolean
operators <literal>&lt;</> and <literal>&gt;</> have a different
precedence than the Boolean operators <literal>&lt;=</> and
<literal>&gt;=</>. Also, you will sometimes need to add
parentheses when using combinations of binary and unary operators.
For instance
<programlisting>
SELECT 5 ! - 6;
</programlisting>
@ -673,7 +677,7 @@ SELECT (5 !) - 6;
This is the price one pays for extensibility.
</para>
<table tocentry="1">
<table id="sql-precedence-table">
<title>Operator Precedence (decreasing)</title>
<tgroup cols="3">
@ -825,7 +829,7 @@ SELECT (5 !) - 6;
SELECT 3 OPERATOR(pg_catalog.+) 4;
</programlisting>
the <literal>OPERATOR</> construct is taken to have the default precedence
shown above for <quote>any other</> operator. This is true no matter
shown in <xref linkend="sql-precedence-table"> for <quote>any other</> operator. This is true no matter
which specific operator name appears inside <literal>OPERATOR()</>.
</para>
</sect2>
@ -901,9 +905,8 @@ SELECT 3 OPERATOR(pg_catalog.+) 4;
</listitem>
<listitem>
<synopsis>( <replaceable>expression</replaceable> )</synopsis>
<para>
Parentheses are used to group subexpressions and override precedence.
Another value expression in parentheses, useful to group subexpressions and override precedence.
</para>
</listitem>
</itemizedlist>
@ -928,21 +931,30 @@ SELECT 3 OPERATOR(pg_catalog.+) 4;
<title>Column References</title>
<para>
A column can be referenced in the form:
A column can be referenced in the form
<synopsis>
<replaceable>correlation</replaceable>.<replaceable>columnname</replaceable> `['<replaceable>subscript</replaceable>`]'
<replaceable>correlation</replaceable>.<replaceable>columnname</replaceable>
</synopsis>
or
<synopsis>
<replaceable>correlation</replaceable>.<replaceable>columnname</replaceable>[<replaceable>subscript</replaceable>]
</synopsis>
(Here, the brackets <literal>[ ]</literal> are meant to appear literally.)
</para>
<para>
<replaceable>correlation</replaceable> is the name of a
table (possibly qualified), or an alias for a table defined by means of a
FROM clause, or
<literal>FROM</literal> clause, or
the key words <literal>NEW</literal> or <literal>OLD</literal>.
(NEW and OLD can only appear in rules,
(<literal>NEW</literal> and <literal>OLD</literal> can only appear in rewrite rules,
while other correlation names can be used in any SQL statement.)
The correlation name and separating dot may be omitted if the column name
is unique
across all the tables being used in the current query. If
<replaceable>column</replaceable> is of an array type, then the
is unique across all the tables being used in the current query. (See also <xref linkend="queries">.)
</para>
<para>
If <replaceable>column</replaceable> is of an array type, then the
optional <replaceable>subscript</replaceable> selects a specific
element or elements in the array. If no subscript is provided, then the
whole array is selected. (See <xref linkend="arrays"> for more about
@ -968,9 +980,9 @@ $<replaceable>number</replaceable>
<function>dept</function>, as
<programlisting>
CREATE FUNCTION dept (text) RETURNS dept
AS 'SELECT * FROM dept WHERE name = $1'
LANGUAGE SQL;
CREATE FUNCTION dept(text) RETURNS dept
AS 'SELECT * FROM dept WHERE name = $1'
LANGUAGE SQL;
</programlisting>
Here the <literal>$1</literal> will be replaced by the first
@ -993,7 +1005,7 @@ CREATE FUNCTION dept (text) RETURNS dept
keywords <token>AND</token>, <token>OR</token>, and
<token>NOT</token>, or is a qualified operator name
<synopsis>
<literal>OPERATOR(</><replaceable>schema</><literal>.</><replaceable>operatorname</><literal>)</>
<literal>OPERATOR(</><replaceable>schema</><literal>.</><replaceable>operatorname</><literal>)</>
</synopsis>
Which particular operators exist and whether
they are unary or binary depends on what operators have been
@ -1042,12 +1054,12 @@ sqrt(2)
output value, such as the sum or average of the inputs. The
syntax of an aggregate expression is one of the following:
<simplelist>
<member><replaceable>aggregate_name</replaceable> (<replaceable>expression</replaceable>)</member>
<member><replaceable>aggregate_name</replaceable> (ALL <replaceable>expression</replaceable>)</member>
<member><replaceable>aggregate_name</replaceable> (DISTINCT <replaceable>expression</replaceable>)</member>
<member><replaceable>aggregate_name</replaceable> ( * )</member>
</simplelist>
<synopsis>
<replaceable>aggregate_name</replaceable> (<replaceable>expression</replaceable>)
<replaceable>aggregate_name</replaceable> (ALL <replaceable>expression</replaceable>)
<replaceable>aggregate_name</replaceable> (DISTINCT <replaceable>expression</replaceable>)
<replaceable>aggregate_name</replaceable> ( * )
</synopsis>
where <replaceable>aggregate_name</replaceable> is a previously
defined aggregate (possibly a qualified name), and
@ -1101,7 +1113,7 @@ sqrt(2)
CAST ( <replaceable>expression</replaceable> AS <replaceable>type</replaceable> )
<replaceable>expression</replaceable>::<replaceable>type</replaceable>
</synopsis>
The <literal>CAST</> syntax conforms to SQL92; the syntax with
The <literal>CAST</> syntax conforms to SQL; the syntax with
<literal>::</literal> is historical <productname>PostgreSQL</productname>
usage.
</para>
@ -1123,8 +1135,8 @@ CAST ( <replaceable>expression</replaceable> AS <replaceable>type</replaceable>
to the type that a value expression must produce (for example, when it is
assigned to a table column); the system will automatically apply a
type cast in such cases. However, automatic casting is only done for
cast functions that are marked <quote>OK to apply implicitly</>
in the system catalogs. Other cast functions must be invoked with
casts that are marked <quote>OK to apply implicitly</>
in the system catalogs. Other casts must be invoked with
explicit casting syntax. This restriction is intended to prevent
surprising conversions from being applied silently.
</para>
@ -1143,6 +1155,13 @@ CAST ( <replaceable>expression</replaceable> AS <replaceable>type</replaceable>
double-quoted, because of syntactic conflicts. Therefore, the use of
the function-like cast syntax leads to inconsistencies and should
probably be avoided in new applications.
(The function-like syntax is in fact just a function call. When
one of the two standard cast syntaxes is used to do a run-time
conversion, it will internally invoke a registered function to
perform the conversion. By convention, these conversion functions
have the same name as their output type, but this is not something
that a portable application should rely on.)
</para>
</sect2>
@ -1151,8 +1170,9 @@ CAST ( <replaceable>expression</replaceable> AS <replaceable>type</replaceable>
<para>
A scalar subquery is an ordinary
<command>SELECT</command> in parentheses that returns exactly one
row with one column. The <command>SELECT</command> query is executed
<command>SELECT</command> query in parentheses that returns exactly one
row with one column. (See <xref linkend="queries"> for information about writing queries.)
The <command>SELECT</command> query is executed
and the single returned value is used in the surrounding value expression.
It is an error to use a query that
returns more than one row or more than one column as a scalar subquery.
@ -1168,7 +1188,7 @@ CAST ( <replaceable>expression</replaceable> AS <replaceable>type</replaceable>
state:
<programlisting>
SELECT name, (SELECT max(pop) FROM cities WHERE cities.state = states.name)
FROM states;
FROM states;
</programlisting>
</para>
</sect2>
@ -1202,25 +1222,26 @@ SELECT somefunc() OR true;
<para>
As a consequence, it is unwise to use functions with side effects
as part of complex expressions. It is particularly dangerous to
rely on side effects or evaluation order in WHERE and HAVING clauses,
rely on side effects or evaluation order in <literal>WHERE</> and <literal>HAVING</> clauses,
since those clauses are extensively reprocessed as part of
developing an execution plan. Boolean
expressions (AND/OR/NOT combinations) in those clauses may be reorganized
expressions (<literal>AND</>/<literal>OR</>/<literal>NOT</> combinations) in those clauses may be reorganized
in any manner allowed by the laws of Boolean algebra.
</para>
<para>
When it is essential to force evaluation order, a CASE construct may
be used. For example, this is an untrustworthy way of trying to
avoid division by zero in a WHERE clause:
When it is essential to force evaluation order, a <literal>CASE</>
construct (see <xref linkend="functions-conditional">) may be
used. For example, this is an untrustworthy way of trying to
avoid division by zero in a <literal>WHERE</> clause:
<programlisting>
SELECT ... WHERE x &lt;&gt; 0 AND y/x &gt; 1.5;
</programlisting>
but this is safe:
But this is safe:
<programlisting>
SELECT ... WHERE CASE WHEN x &lt;&gt; 0 THEN y/x &gt; 1.5 ELSE false END;
</programlisting>
A CASE construct used in this fashion will defeat optimization attempts,
A <literal>CASE</> construct used in this fashion will defeat optimization attempts,
so it should only be done when necessary.
</para>
</sect2>

24
doc/src/sgml/typeconv.sgml
View File

@ -1,9 +1,6 @@
<chapter Id="typeconv">
<title>Type Conversion</title>
<sect1 id="typeconv-intro">
<title>Introduction</title>
<para>
<acronym>SQL</acronym> queries can, intentionally or not, require
mixing of different data types in the same expression.
@ -29,10 +26,9 @@ operators.
</para>
<para>
The <citetitle>Programmer's Guide</citetitle> has more details on the exact algorithms used for
The &cite-programmer; has more details on the exact algorithms used for
implicit type conversion and coercion.
</para>
</sect1>
<sect1 id="typeconv-overview">
<title>Overview</title>
@ -41,7 +37,7 @@ implicit type conversion and coercion.
<acronym>SQL</acronym> is a strongly typed language. That is, every data item
has an associated data type which determines its behavior and allowed usage.
<productname>PostgreSQL</productname> has an extensible type system that is
much more general and flexible than other <acronym>RDBMS</acronym> implementations.
much more general and flexible than other <acronym>SQL</acronym> implementations.
Hence, most type conversion behavior in <productname>PostgreSQL</productname>
should be governed by general rules rather than by <foreignphrase>ad hoc</> heuristics, to allow
mixed-type expressions to be meaningful even with user-defined types.
@ -142,13 +138,13 @@ conventions for the <acronym>SQL</acronym> standard native types such as
</para>
<para>
The <productname>PostgreSQL</productname> parser uses the convention that all
type conversion functions take a single argument of the source type and are
named with the same name as the target type. Any function meeting these
criteria is considered to be a valid conversion function, and may be used
by the parser as such. This simple assumption gives the parser the power
to explore type conversion possibilities without hardcoding, allowing
extended user-defined types to use these same features transparently.
The system catalogs store information about which conversions, called
<firstterm>casts</firstterm>, between data types are valid, and how to
perform those conversions. Additional casts can be added by the user
with the <command>CREATE CAST</command> command. (This is usually
done in conjunction with defining new data types. The set of casts
between the built-in types has been carefully crafted and should not
be altered.)
</para>
<para>
@ -169,7 +165,7 @@ types.
<para>
All type conversion rules are designed with several principles in mind:
<itemizedlist mark="bullet" spacing="compact">
<itemizedlist>
<listitem>
<para>
Implicit conversions should never have surprising or unpredictable outcomes.

8
doc/src/sgml/user-manag.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/user-manag.sgml,v 1.17 2002/10/24 17:48:54 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/user-manag.sgml,v 1.18 2002/11/11 20:14:04 petere Exp $
-->
<chapter id="user-manag">
@ -129,7 +129,7 @@ dropuser <replaceable>name</replaceable>
<para>
A password is only significant if the client authentication
method requires the user to supply a password when connecting
to the database. At present, the <option>password</>,
to the database. The <option>password</>,
<option>md5</>, and <option>crypt</> authentication methods
make use of passwords. Database passwords are separate from
operating system passwords. Specify a password upon user
@ -156,7 +156,7 @@ dropuser <replaceable>name</replaceable>
ALTER USER myname SET enable_indexscan TO off;
</programlisting>
This will save the setting (but not set it immediately) and in
subsequent connections it will appear as though <literal>SET geqo
subsequent connections it will appear as though <literal>SET enable_indexscan
TO off;</literal> had been called right before the session started.
You can still alter this setting during the session; it will only
be the default. To undo any such setting, use <literal>ALTER USER
@ -205,7 +205,7 @@ ALTER GROUP <replaceable>name</replaceable> DROP USER <replaceable>uname1</repla
<literal>USAGE</>, and <literal>ALL PRIVILEGES</>. For more
information on the different types of privileges support by
<productname>PostgreSQL</productname>, refer to the
<command>GRANT</command> reference manual. The right to modify or
<command>GRANT</command> page in the &cite-reference;. The right to modify or
destroy an object is always the privilege of the owner only. To
assign privileges, the <command>GRANT</command> command is
used. So, if <literal>joe</literal> is an existing user, and

4
doc/src/sgml/user.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/user.sgml,v 1.33 2002/10/24 17:48:54 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/user.sgml,v 1.34 2002/11/11 20:14:04 petere Exp $
-->
<book id="user">
@ -29,7 +29,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/Attic/user.sgml,v 1.33 2002/10/24 17:48:54
database, and how to query it. The middle part lists the
available data types and functions for use in SQL data commands.
The rest of the book treats several aspects that are important for
tuning a database for optimial performance.
tuning a database for optimal performance.
</para>
<para>