Skip to content

P
Postgres FD Implementation
Commit 20aae304 authored by Peter Eisentraut's avatar Peter Eisentraut
Browse files
Options

Editing of more reference pages.

parent 3a496c8a
Show whitespace changes
Inline Side-by-side
Showing with 1663 additions and 2691 deletions
doc/src/sgml/ref/abort.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/abort.sgml,v 1.12 2003/04/15 13:25:08 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/abort.sgml,v 1.13 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -32,6 +32,22 @@ ABORT [ WORK | TRANSACTION ]
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><literal>WORK</literal></term>
<term><literal>TRANSACTION</literal></term>
<listitem>
<para>
Optional key words. They have no effect.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Diagnostics</title>
......@@ -71,7 +87,7 @@ ABORT [ WORK | TRANSACTION ]
<para>
To abort all changes:
<programlisting>
ABORT WORK;
ABORT;
</programlisting>
</para>
</refsect1>
......
doc/src/sgml/ref/deallocate.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/deallocate.sgml,v 1.1 2002/08/27 04:55:07 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/deallocate.sgml,v 1.2 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,114 +8,79 @@ PostgreSQL documentation
<refentrytitle id="sql-deallocate-title">DEALLOCATE</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
DEALLOCATE
</refname>
<refpurpose>
remove a prepared query
</refpurpose>
<refname>DEALLOCATE</refname>
<refpurpose>deallocate a prepared statement</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>2002-08-12</date>
</refsynopsisdivinfo>
<synopsis>
DEALLOCATE [ PREPARE ] <replaceable class="PARAMETER">plan_name</replaceable>
</synopsis>
<synopsis>
DEALLOCATE [ PREPARE ] <replaceable class="parameter">plan_name</replaceable>
</synopsis>
</refsynopsisdiv>
<refsect2 id="R2-SQL-DEALLOCATE-1">
<refsect2info>
<date>2002-08-12</date>
</refsect2info>
<title>
Inputs
</title>
<refsect1>
<title>Description</title>
<para>
<command>DEALLOCATE</command> is used to deallocate a previously
prepared SQL statement. If you do not explicitly deallocate a
prepared statement, it is deallocated when the session ends.
</para>
<para>
For more information on prepared statements, see <xref
linkend="sql-prepare" endterm="sql-prepare-title">.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term>PREPARE</term>
<term><literal>PREPARE</literal></term>
<listitem>
<para>
This keyword is ignored.
This key word is ignored.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">plan_name</replaceable></term>
<term><replaceable class="parameter">plan_name</replaceable></term>
<listitem>
<para>
The name of the prepared query to remove.
The name of the prepared statement to deallocate.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="R2-SQL-DEALLOCATE-2">
<refsect2info>
<date>2002-08-12</date>
</refsect2info>
<title>
Outputs
</title>
<para>
</refsect1>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>
<returnvalue>DEALLOCATE</returnvalue>
</computeroutput></term>
<term><computeroutput>DEALLOCATE</computeroutput></term>
<listitem>
<para>
The prepared query was removed successfully.
Message returned if the prepared statement was deallocated successfully.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-DEALLOCATE-1">
<refsect1info>
<date>2002-08-12</date>
</refsect1info>
<title>
Description
</title>
<para>
<command>DEALLOCATE</command> is used to remove a previously
prepared query. If you do not explicitly
<command>DEALLOCATE</command> a prepared query, it is removed when
the session ends.
</para>
<para>
For more information on prepared queries, see <xref
linkend="sql-prepare" endterm="sql-prepare-title">.
</para>
</refsect1>
<refsect1 id="R1-SQL-DEALLOCATE-2">
<title>
Compatibility
</title>
<refsect1>
<title>Compatibility</title>
<refsect2 id="R2-SQL-DEALLOCATE-3">
<refsect2info>
<date>2002-08-12</date>
</refsect2info>
<title>
SQL92
</title>
<para>
SQL92 includes a <command>DEALLOCATE</command> statement, but it is
only for use in embedded SQL clients.
The SQL standard includes a <command>DEALLOCATE</command>
statement, but it is only for use in embedded SQL.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/delete.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/delete.sgml,v 1.16 2002/04/23 02:07:16 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/delete.sgml,v 1.17 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,31 +8,54 @@ PostgreSQL documentation
<refentrytitle id="SQL-DELETE-TITLE">DELETE</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
DELETE
</refname>
<refpurpose>
delete rows of a table
</refpurpose>
<refnamediv>
<refname>DELETE</refname>
<refpurpose>delete rows of a table</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1999-07-20</date>
</refsynopsisdivinfo>
<synopsis>
<synopsis>
DELETE FROM [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ WHERE <replaceable class="PARAMETER">condition</replaceable> ]
</synopsis>
<refsect2 id="R2-SQL-DELETE-1">
<refsect2info>
<date>1998-04-15</date>
</refsect2info>
<title>
Inputs
</title>
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>DELETE</command> deletes rows that satisfy the
<literal>WHERE</literal> clause from the specified table. If the
<literal>WHERE</literal> clause is absent, the effect is to delete
all rows in the table. The result is a valid, but empty table.
</para>
<tip>
<para>
<xref linkend="sql-truncate" endterm="sql-truncate-title"> is a
<productname>PostgreSQL</productname> extension which provides a
faster mechanism to remove all rows from a table.
</para>
</tip>
<para>
By default, <command>DELETE</command> will delete rows in the
specified table and all its subtables. If you wish to only delete
from the specific table mentioned, you must use the
<literal>ONLY</literal> clause.
</para>
<para>
You must have the <literal>DELETE</literal> privilege on the table
to delete from it, as well as the <literal>SELECT</literal>
privilege to any table whose values are read in the <replaceable
class="parameter">condition</replaceable>.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="parameter">table</replaceable></term>
......@@ -42,111 +65,46 @@ DELETE FROM [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ WHERE
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">condition</replaceable></term>
<listitem>
<para>
This is an SQL selection query which returns the rows which
are to be deleted.
</para>
<para>
Refer to the SELECT statement for further description
of the WHERE clause.
A value expression that returns a value of type
<type>boolean</type> that determines the rows which are to be
deleted.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="R2-SQL-DELETE-2">
<refsect2info>
<date>1998-04-15</date>
</refsect2info>
<title>
Outputs
</title>
<para>
</refsect1>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>
DELETE <replaceable class="parameter">count</replaceable>
</computeroutput></term>
<term><computeroutput>DELETE <replaceable class="parameter">count</replaceable></computeroutput></term>
<listitem>
<para>
Message returned if items are successfully deleted. The
Message returned if rows are successfully deleted. The
<replaceable class="parameter">count</replaceable> is the number
of rows deleted.
</para>
<para>
If <replaceable class="parameter">count</replaceable> is 0,
no rows were deleted.
of rows deleted. If <replaceable
class="parameter">count</replaceable> is 0, no rows were
deleted.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-DELETE-1">
<refsect1info>
<date>1998-04-15</date>
</refsect1info>
<title>
Description
</title>
<para>
<command>DELETE</command> removes rows which satisfy the WHERE
clause from the specified table.
</para>
<para>
If the <firstterm>condition</firstterm> (WHERE clause) is absent,
the effect is to delete all rows in the table.
The result is a valid, but empty table.
<tip>
<para>
<xref linkend="sql-truncate" endterm="sql-truncate-title"> is a
<productname>PostgreSQL</productname> extension which provides a
faster mechanism to remove all rows from a table.
</para>
</tip>
</para>
<para>
By default DELETE will delete tuples in the table specified
and all its sub-tables. If you wish to only update the
specific table mentioned, you should use the ONLY clause.
</para>
<para>
You must have write access to the table in order to modify
it, as well as read access to any table whose values are
read in the <replaceable class="parameter">condition</replaceable>.
</para>
</refsect1>
<refsect1 id="R1-SQL-DELETE-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
Remove all films but musicals:
Delete all films but musicals:
<programlisting>
DELETE FROM films WHERE kind &lt;&gt; 'Musical';
SELECT * FROM films;
<computeroutput>
code | title | did | date_prod | kind | len
-------+---------------------------+-----+------------+---------+-------
UA501 | West Side Story | 105 | 1961-01-03 | Musical | 02:32
TC901 | The King and I | 109 | 1956-08-11 | Musical | 02:13
WD101 | Bed Knobs and Broomsticks | 111 | | Musical | 01:57
(3 rows)
</computeroutput>
</programlisting>
</para>
......@@ -154,42 +112,16 @@ SELECT * FROM films;
Clear the table <literal>films</literal>:
<programlisting>
DELETE FROM films;
SELECT * FROM films;
<computeroutput>
code | title | did | date_prod | kind | len
------+-------+-----+-----------+------+-----
(0 rows)
</computeroutput>
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-DELETE-3">
<title>
Compatibility
</title>
<refsect2 id="R2-SQL-DELETE-4">
<refsect2info>
<date>1998-04-15</date>
</refsect2info>
<title>
SQL92
</title>
<para>
<acronym>SQL92</acronym> allows a positioned DELETE statement:
<synopsis>
DELETE FROM <replaceable class="parameter">table</replaceable> WHERE
CURRENT OF <replaceable class="parameter">cursor</replaceable>
</synopsis>
<refsect1>
<title>Compatibility</title>
where <replaceable class="parameter">cursor</replaceable>
identifies an open cursor.
Interactive cursors in <productname>PostgreSQL</productname> are read-only.
<para>
This command conforms to the SQL standard.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/end.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/end.sgml,v 1.8 2002/04/21 19:02:39 thomas Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/end.sgml,v 1.9 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,145 +8,99 @@ PostgreSQL documentation
<refentrytitle id="SQL-END-TITLE">END</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
END
</refname>
<refpurpose>
commit the current transaction
</refpurpose>
<refname>END</refname>
<refpurpose>commit the current transaction</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1999-07-20</date>
</refsynopsisdivinfo>
<synopsis>
<synopsis>
END [ WORK | TRANSACTION ]
</synopsis>
<refsect2 id="R2-SQL-END-1">
<refsect2info>
<date>1998-09-08</date>
</refsect2info>
<title>
Inputs
</title>
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>END</command> commits the current transaction. All changes
made by the transaction become visible to others and are guaranteed
to be durable if a crash occurs. It is a PostgreSQL extension that
is equivalent to <xref linkend="sql-commit"
endterm="sql-commit-title">.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term>WORK</term>
<term>TRANSACTION</term>
<term><literal>WORK</literal></term>
<term><literal>TRANSACTION</literal></term>
<listitem>
<para>
Optional keywords. They have no effect.
Optional key words. They have no effect.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="R2-SQL-END-2">
<refsect2info>
<date>1998-09-08</date>
</refsect2info>
<title>
Outputs
</title>
<para>
</refsect1>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>
COMMIT
</computeroutput></term>
<term><computeroutput>COMMIT</computeroutput></term>
<listitem>
<para>
Message returned if the transaction is successfully committed.
Message returned if the transaction was successfully committed.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><computeroutput>
WARNING: COMMIT: no transaction in progress
</computeroutput></term>
<term><computeroutput>WARNING: COMMIT: no transaction in progress</computeroutput></term>
<listitem>
<para>
If there is no transaction in progress.
Message if there is no transaction in progress.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-END-1">
<refsect1info>
<date>1998-09-08</date>
</refsect1info>
<title>
Description
</title>
<para>
<command>END</command> is a <productname>PostgreSQL</productname>
extension, and is a synonym for the SQL92-compatible
<xref linkend="sql-commit" endterm="sql-commit-title">.
</para>
</refsect1>
<refsect2 id="R2-SQL-END-3">
<refsect2info>
<date>1998-09-08</date>
</refsect2info>
<title>
Notes
</title>
<para>
The keywords WORK and TRANSACTION are noise and can be omitted.
</para>
<refsect1>
<title>Notes</title>
<para>
Use <xref linkend="SQL-ROLLBACK" endterm="SQL-ROLLBACK-TITLE">
to abort a transaction.
Use <xref linkend="SQL-ROLLBACK" endterm="SQL-ROLLBACK-TITLE"> to
abort a transaction.
</para>
</refsect2>
</refsect1>
<refsect1 id="R1-SQL-END-2">
<title>
Usage
</title>
<para>
To make all changes permanent:
<refsect1>
<title>Examples</title>
<programlisting>
END WORK;
</programlisting>
<para>
To commit the current transaction and make all changes permanent:
<programlisting>
END;
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-END-3">
<title>
Compatibility
</title>
<refsect2 id="R2-SQL-END-4">
<refsect2info>
<date>1998-09-08</date>
</refsect2info>
<title>
SQL92
</title>
<refsect1>
<title>Compatibility</title>
<para>
<command>END</command> is a <productname>PostgreSQL</productname>
extension which provides functionality equivalent to
<xref linkend="sql-commit" endterm="sql-commit-title">.
extension that provides functionality equivalent to <xref
linkend="sql-commit" endterm="sql-commit-title">, which is
specified in the SQL standard.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/execute.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/execute.sgml,v 1.3 2003/02/02 23:46:37 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/execute.sgml,v 1.4 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,37 +8,60 @@ PostgreSQL documentation
<refentrytitle id="sql-execute-title">EXECUTE</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
EXECUTE
</refname>
<refpurpose>
execute a prepared query
</refpurpose>
<refname>EXECUTE</refname>
<refpurpose>execute a prepared statement</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>2002-08-12</date>
</refsynopsisdivinfo>
<synopsis>
EXECUTE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable class="PARAMETER">parameter</replaceable> [, ...] ) ] [ INTO [ TEMPORARY | TEMP ] <replaceable class="PARAMETER">table</replaceable> ]
</synopsis>
<synopsis>
EXECUTE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable class="PARAMETER">parameter</replaceable> [, ...] ) ] [ INTO [ TEMPORARY | TEMP ] <replaceable class="PARAMETER">table</replaceable> ]
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>EXECUTE</command> is used to execute a previously prepared
statement. Since prepared statements only exist for the duration of a
session, the prepared statement must have been created by a
<command>PREPARE</command> statement executed earlier in the
current session.
</para>
<para>
If the <command>PREPARE</command> statement that created the statement
specified some parameters, a compatible set of parameters must be
passed to the <command>EXECUTE</command> statement, or else an
error is raised. Note that (unlike functions) prepared statements are
not overloaded based on the type or number of their parameters; the
name of a prepared statement must be unique within a database session.
</para>
<refsect2 id="R2-SQL-EXECUTE-1">
<refsect2info>
<date>2002-08-12</date>
</refsect2info>
<title>
Inputs
</title>
<para>
Like <command>SELECT INTO</command>, <command>EXECUTE</command> can
store the results of executing a query into a newly-created
table, by specifying an <literal>INTO</> clause. For more information on this behavior,
see <xref linkend="sql-selectinto" endterm="sql-selectinto-title">.
</para>
<para>
For more information on the creation and usage of prepared statements,
see <xref linkend="sql-prepare" endterm="sql-prepare-title">.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="PARAMETER">plan_name</replaceable></term>
<listitem>
<para>
The name of the prepared query to execute.
The name of the prepared statement to execute.
</para>
</listitem>
</varlistentry>
......@@ -47,11 +70,11 @@ PostgreSQL documentation
<term><replaceable class="PARAMETER">parameter</replaceable></term>
<listitem>
<para>
The actual value of a parameter to the prepared query. This
must be an expression yielding a value of a type compatible
with the data-type specified for this parameter position in
the <command>PREPARE</command> statement that created the
prepared query.
The actual value of a parameter to the prepared statement. This
must be an expression yielding a value of a type compatible with
the data type specified for this parameter position in the
<command>PREPARE</command> command that created the prepared
statement.
</para>
</listitem>
</varlistentry>
......@@ -60,76 +83,25 @@ PostgreSQL documentation
<term><replaceable class="PARAMETER">table</replaceable></term>
<listitem>
<para>
The name of the table in which to store the results of
executing the query (if it is a <command>SELECT</command>). If
no table is specified, the results are returned to the client
(as normal).
The name of the table in which to store the results of executing
the statement (if it is a <command>SELECT</command>). If no
table is specified, the results are returned to the client (as
normal).
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-EXECUTE-1">
<refsect1info>
<date>2002-08-12</date>
</refsect1info>
<title>
Description
</title>
<para>
<command>EXECUTE</command> is used to execute a previously prepared
query. Since prepared queries only exist for the duration of a
session, the prepared query must have been created by a
<command>PREPARE</command> statement executed earlier in the
current session.
</para>
<para>
If the <command>PREPARE</command> statement that created the query
specified some parameters, a compatible set of parameters must be
passed to the <command>EXECUTE</command> statement, or else an
error is raised. Note that (unlike functions) prepared queries are
not overloaded based on the type or number of their parameters: the
name of a prepared query must be unique within a database session.
</para>
<para>
Like <command>SELECT INTO</command>, <command>EXECUTE</command> can
store the results of executing the query into a newly-created
table, by specifying an INTO clause. For more information on this behavior,
see <xref linkend="sql-selectinto" endterm="sql-selectinto-title">.
</para>
<para>
For more information on the creation and usage of prepared queries,
see <xref linkend="sql-prepare" endterm="sql-prepare-title">.
</para>
</refsect1>
<refsect1 id="R1-SQL-EXECUTE-2">
<title>
Compatibility
</title>
<refsect1>
<title>Compatibility</title>
<refsect2 id="R2-SQL-EXECUTE-2">
<refsect2info>
<date>2002-08-12</date>
</refsect2info>
<title>
SQL92
</title>
<para>
SQL92 includes an <command>EXECUTE</command> statement, but it is
only for use in embedded SQL clients. The
<command>EXECUTE</command> statement implemented by
<productname>PostgreSQL</productname> also uses a somewhat
different syntax.
The SQL standard includes an <command>EXECUTE</command> statement,
but it is only for use in embedded SQL. This version of the
<command>EXECUTE</command> statement also uses a somewhat different
syntax.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/explain.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/explain.sgml,v 1.25 2003/03/25 16:15:41 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/explain.sgml,v 1.26 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,255 +8,212 @@ PostgreSQL documentation
<refentrytitle id="SQL-EXPLAIN-TITLE">EXPLAIN</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
EXPLAIN
</refname>
<refpurpose>
show the execution plan of a statement
</refpurpose>
<refname>EXPLAIN</refname>
<refpurpose>show the execution plan of a statement</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1999-07-20</date>
</refsynopsisdivinfo>
<synopsis>
EXPLAIN [ ANALYZE ] [ VERBOSE ] <replaceable class="PARAMETER">query</replaceable>
</synopsis>
<refsect2 id="R2-SQL-EXPLAIN-1">
<refsect2info>
<date>1998-09-01</date>
</refsect2info>
<title>
Inputs
</title>
<synopsis>
EXPLAIN [ ANALYZE ] [ VERBOSE ] <replaceable class="parameter">statement</replaceable>
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
This command displays the execution plan that the
<productname>PostgreSQL</productname> planner generates for the
supplied statenebt. The execution plan shows how the table(s)
referenced by the statement will be scanned---by plain sequential scan,
index scan, etc.---and if multiple tables are referenced, what join
algorithms will be used to bring together the required row from
each input table.
</para>
<variablelist>
<varlistentry>
<term>ANALYZE</term>
<listitem>
<para>
Flag to carry out the query and show actual run times.
The most critical part of the display is the estimated statement execution
cost, which is the planner's guess at how long it will take to run the
statement (measured in units of disk page fetches). Actually two numbers
are shown: the start-up time before the first row can be returned, and
the total time to return all the rows. For most queries the total time
is what matters, but in contexts such as a subquery in <literal>EXISTS</literal>, the planner
will choose the smallest start-up time instead of the smallest total time
(since the executor will stop after getting one row, anyway).
Also, if you limit the number of rows to return with a <literal>LIMIT</literal> clause,
the planner makes an appropriate interpolation between the endpoint
costs to estimate which plan is really the cheapest.
</para>
</listitem>
</varlistentry>
<para>
The <literal>ANALYZE</literal> option causes the statement to be actually executed, not only
planned. The total elapsed time expended within each plan node (in
milliseconds) and total number of rows it actually returned are added to
the display. This is useful for seeing whether the planner's estimates
are close to reality.
</para>
<important>
<para>
Keep in mind that the statement is actually executed when
<literal>ANALYZE</literal> is used. Although
<command>EXPLAIN</command> will discard any output that a
<command>SELECT</command> would return, other side effects of the
statement will happen as usual. If you wish to use
<command>EXPLAIN ANALYZE</command> on an
<command>INSERT</command>, <command>UPDATE</command>,
<command>DELETE</command>, or <command>EXECUTE</command> statement
without letting the command affect your data, use this approach:
<programlisting>
BEGIN;
EXPLAIN ANALYZE ...;
ROLLBACK;
</programlisting>
</para>
</important>
</refsect1>
<refsect1>
<title>Parameter</title>
<variablelist>
<varlistentry>
<term>VERBOSE</term>
<term><literal>ANALYZE</literal></term>
<listitem>
<para>
Flag to show detailed query plan dump.
Carry out the command and show the actual run times.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">query</replaceable></term>
<term><literal>VERBOSE</literal></term>
<listitem>
<para>
Any <command>SELECT</>, <command>INSERT</>, <command>UPDATE</>,
<command>DELETE</>, <command>EXECUTE</>,
or <command>DECLARE CURSOR</> query.
Show the full internal representation of the plan tree, rather
than just a summary. Usually this option is only useful for
debugging <productname>PostgreSQL</productname>. The
<literal>VERBOSE</literal> output is either pretty-printed or
not, depending on the setting of the
<varname>explain_pretty_print</varname> configuration parameter.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="R2-SQL-EXPLAIN-2">
<refsect2info>
<date>1998-04-15</date>
</refsect2info>
<title>
Outputs
</title>
<para>
<variablelist>
<varlistentry>
<term>Query plan</term>
<term><replaceable class="parameter">statement</replaceable></term>
<listitem>
<para>
Explicit query plan from the <productname>PostgreSQL</productname>
planner.
Any <command>SELECT</>, <command>INSERT</>, <command>UPDATE</>,
<command>DELETE</>, <command>EXECUTE</>, or <command>DECLARE</>
statement, whose execution plan you wish to see.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<note>
<para>
Prior to <productname>PostgreSQL</productname> 7.3, the query
plan was emitted in the form of a <literal>NOTICE</literal>
message. Now it appears as a query result (formatted like a
table with a single text column).
</para>
</note>
</refsect2>
</refsynopsisdiv>
</refsect1>
<refsect1 id="R1-SQL-EXPLAIN-1">
<refsect1info>
<date>1998-04-15</date>
</refsect1info>
<title>
Description
</title>
<refsect1>
<title>Diagnostics</title>
<para>
This command displays the execution plan that the
<productname>PostgreSQL</productname> planner generates for the
supplied query. The execution plan shows how the table(s)
referenced by the query will be scanned---by plain sequential scan,
index scan, etc.---and if multiple tables are referenced, what join
algorithms will be used to bring together the required tuples from
each input table.
<command>EXPLAIN</command> prints the execution plan of the
specified statement from the <productname>PostgreSQL</productname>
planner.
</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>
The most critical part of the display is the estimated query execution
cost, which is the planner's guess at how long it will take to run the
query (measured in units of disk page fetches). Actually two numbers
are shown: the start-up time before the first tuple can be returned, and
the total time to return all the tuples. For most queries the total time
is what matters, but in contexts such as an EXISTS sub-query the planner
will choose the smallest start-up time instead of the smallest total time
(since the executor will stop after getting one tuple, anyway).
Also, if you limit the number of tuples to return with a LIMIT clause,
the planner makes an appropriate interpolation between the endpoint
costs to estimate which plan is really the cheapest.
There is only sparse documentation on the optimizer's use of cost
information in <productname>PostgreSQL</productname>. Refer to
<xref linkend="using-explain"> for more information.
</para>
<note>
<para>
In order to allow the <productname>PostgreSQL</productname> query
planner to make reasonably informed decisions when optimizing
queries, the <command>ANALYZE</command> statement should be run
to record statistics about the distribution of data within the
table. If you have not done this (or if the statistical distribution
of the data in the table has changed significantly since the last
time <command>ANALYZE</command> was run), the estimated costs
are unlikely to conform to the real properties of the query,
and consequently an inferior query plan may be chosen.
queries, the <command>ANALYZE</command> statement should be run to
record statistics about the distribution of data within the
table. If you have not done this (or if the statistical
distribution of the data in the table has changed significantly
since the last time <command>ANALYZE</command> was run), the
estimated costs are unlikely to conform to the real properties of
the query, and consequently an inferior query plan may be chosen.
</para>
</note>
<para>
The ANALYZE option causes the query to be actually executed, not only
planned. The total elapsed time expended within each plan node (in
milliseconds) and total number of rows it actually returned are added to
the display. This is useful for seeing whether the planner's estimates
are close to reality.
</para>
<caution>
<para>
Keep in mind that the query is actually executed when ANALYZE is used.
Although <command>EXPLAIN</command> will discard any output that a SELECT
would return,
other side-effects of the query will happen as usual.
If you wish to use <command>EXPLAIN ANALYZE</command> on an INSERT,
UPDATE, DELETE, or EXECUTE query without letting the query affect your
data, use this approach:
<programlisting>
BEGIN;
EXPLAIN ANALYZE ...;
ROLLBACK;
</programlisting>
</para>
</caution>
<para>
The VERBOSE option emits the full internal representation of the plan tree,
rather than just a summary.
Usually this option is only useful for debugging
<productname>PostgreSQL</productname>. The VERBOSE dump is either
pretty-printed or not, depending on the setting of the
<option>EXPLAIN_PRETTY_PRINT</option> configuration parameter.
</para>
<refsect2 id="R2-SQL-EXPLAIN-3">
<refsect2info>
<date>1998-04-15</date>
</refsect2info>
<title>
Notes
</title>
<para>
There is only sparse documentation on the optimizer's use of cost
information in <productname>PostgreSQL</productname>.
Refer to <xref linkend="using-explain"> for more information.
Prior to <productname>PostgreSQL</productname> 7.3, the plan was
emitted in the form of a <literal>NOTICE</literal> message. Now it
appears as a query result (formatted like a table with a single
text column).
</para>
</refsect2>
</refsect1>
<refsect1 id="R1-SQL-EXPLAIN-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
To show a query plan for a simple query on a table with a single
<type>int4</type> column and 10000 rows:
To show the plan for a simple query on a table with a single
<type>integer</type> column and 10000 rows:
<programlisting>
<programlisting>
EXPLAIN SELECT * FROM foo;
<computeroutput>
QUERY PLAN
---------------------------------------------------------
Seq Scan on foo (cost=0.00..155.00 rows=10000 width=4)
(1 row)
</computeroutput>
</programlisting>
</programlisting>
</para>
<para>
If there is an index and we use a query with an indexable WHERE condition,
<command>EXPLAIN</command> will show a different plan:
If there is an index and we use a query with an indexable
<literal>WHERE</literal> condition, <command>EXPLAIN</command>
might show a different plan:
<programlisting>
<programlisting>
EXPLAIN SELECT * FROM foo WHERE i = 4;
<computeroutput>
QUERY PLAN
--------------------------------------------------------------
Index Scan using fi on foo (cost=0.00..5.98 rows=1 width=4)
Index Cond: (i = 4)
(2 rows)
</computeroutput>
</programlisting>
</programlisting>
</para>
<para>
And here is an example of a query plan for a query
using an aggregate function:
<programlisting>
<programlisting>
EXPLAIN SELECT sum(i) FROM foo WHERE i &lt; 10;
<computeroutput>
QUERY PLAN
---------------------------------------------------------------------
Aggregate (cost=23.93..23.93 rows=1 width=4)
-&gt; Index Scan using fi on foo (cost=0.00..23.92 rows=6 width=4)
Index Cond: (i &lt; 10)
(3 rows)
</computeroutput>
</programlisting>
</programlisting>
</para>
<para>
Here is an example of using EXPLAIN EXECUTE to display the query
plan for a prepared query:
Here is an example of using <command>EXPLAIN EXECUTE</command> to
display the execution plan for a prepared query:
<programlisting>
<programlisting>
PREPARE query(int, int) AS SELECT sum(bar) FROM test
WHERE id &gt; $1 AND id &lt; $2
GROUP BY foo;
EXPLAIN ANALYZE EXECUTE query(100, 200);
<computeroutput>
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------
HashAggregate (cost=39.53..39.53 rows=1 width=8) (actual time=0.66..0.67 rows=7 loops=1)
......@@ -264,38 +221,28 @@ EXPLAIN ANALYZE EXECUTE query(100, 200);
Index Cond: ((id &gt; $1) AND (id &lt; $2))
Total runtime: 0.85 msec
(4 rows)
</computeroutput>
</programlisting>
</programlisting>
</para>
<para>
Note that the specific numbers shown, and even the selected query
strategy, may vary between <productname>PostgreSQL</productname>
releases due to planner improvements. In addition, the
<command>ANALYZE</command> command uses random sampling to estimate
data statistics; therefore, it is possible
for cost estimates to change after a fresh run of
Of course, the specific numbers shown here depend on the actual
contents of the tables involved. Also note that the numbers, and
even the selected query strategy, may vary between
<productname>PostgreSQL</productname> releases due to planner
improvements. In addition, the <command>ANALYZE</command> command
uses random sampling to estimate data statistics; therefore, it is
possible for cost estimates to change after a fresh run of
<command>ANALYZE</command>, even if the actual distribution of data
in the table has not changed.
</para>
</refsect1>
<refsect1 id="R1-SQL-EXPLAIN-3">
<title>
Compatibility
</title>
<refsect2 id="R2-SQL-EXPLAIN-4">
<refsect2info>
<date>1998-09-01</date>
</refsect2info>
<title>
SQL92
</title>
<refsect1>
<title>Compatibility</title>
<para>
There is no <command>EXPLAIN</command> statement defined in SQL92.
There is no <command>EXPLAIN</command> statement defined in the SQL standard.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/grant.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/grant.sgml,v 1.32 2003/01/23 23:38:53 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/grant.sgml,v 1.33 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -43,10 +43,10 @@ GRANT { { CREATE | USAGE } [,...] | ALL [ PRIVILEGES ] }
<title>Description</title>
<para>
The <command>GRANT</command> command gives specific permissions on
The <command>GRANT</command> command gives specific privileges on
an object (table, view, sequence, database, function, procedural language,
or schema) to
one or more users or groups of users. These permissions are added
one or more users or groups of users. These privileges are added
to those already granted, if any.
</para>
......@@ -55,18 +55,18 @@ GRANT { { CREATE | USAGE } [,...] | ALL [ PRIVILEGES ] }
privileges are to be granted to all users, including those that may
be created later. <literal>PUBLIC</literal> may be thought of as an
implicitly defined group that always includes all users.
Note that any particular user will have the sum
Any particular user will have the sum
of privileges granted directly to him, privileges granted to any group he
is presently a member of, and privileges granted to
<literal>PUBLIC</literal>.
</para>
<para>
There is no need to grant privileges to the creator of an object,
as the creator has all privileges by default. (The creator could,
There is no need to grant privileges to the owner of an object (usually the user that created it),
as the owner has all privileges by default. (The owner could,
however, choose to revoke some of his own privileges for safety.)
Note that the right to drop an object, or to alter it in any way is
not described by a grantable right; it is inherent in the creator,
The right to drop an object, or to alter it in any way is
not described by a grantable right; it is inherent in the owner,
and cannot be granted or revoked.
</para>
......@@ -84,7 +84,7 @@ GRANT { { CREATE | USAGE } [,...] | ALL [ PRIVILEGES ] }
<literal>TEMP</> table creation privilege for databases;
<literal>EXECUTE</> privilege for functions; and
<literal>USAGE</> privilege for languages.
The object creator may of course revoke these privileges. (For maximum
The object owner may of course revoke these privileges. (For maximum
security, issue the <command>REVOKE</> in the same transaction that
creates the object; then there is no window in which another user
may use the object.)
......@@ -252,7 +252,7 @@ GRANT { { CREATE | USAGE } [,...] | ALL [ PRIVILEGES ] }
</para>
<para>
It should be noted that database <firstterm>superusers</> can access
It should be noted that database superusers can access
all objects regardless of object privilege settings. This
is comparable to the rights of <literal>root</> in a Unix system.
As with <literal>root</>, it's unwise to operate as a superuser
......@@ -267,17 +267,18 @@ GRANT { { CREATE | USAGE } [,...] | ALL [ PRIVILEGES ] }
</para>
<para>
Use <xref linkend="app-psql">'s <command>\dp</command> command
Use <xref linkend="app-psql">'s <command>\z</command> command
to obtain information about existing privileges, for example:
<programlisting>
lusitania=> \dp mytable
=> \z mytable
Access privileges for database "lusitania"
Schema | Table | Access privileges
--------+---------+---------------------------------------
public | mytable | {=r/postgres,miriam=arwdRxt/postgres,"group todos=arw/postgres"}
(1 row)
</programlisting>
The entries shown by <command>\dp</command> are interpreted thus:
The entries shown by <command>\z</command> are interpreted thus:
<programlisting>
=xxxx -- privileges granted to PUBLIC
uname=xxxx -- privileges granted to a user
......@@ -305,14 +306,14 @@ lusitania=> \dp mytable
<programlisting>
GRANT SELECT ON mytable TO PUBLIC;
GRANT SELECT,UPDATE,INSERT ON mytable TO GROUP todos;
GRANT SELECT, UPDATE, INSERT ON mytable TO GROUP todos;
</programlisting>
</para>
<para>
If the <quote>Access privileges</> column is empty for a given object,
it means the object has default privileges (that is, its privileges field
is NULL). Default privileges always include all privileges for the owner,
it means the object has default privileges (that is, its privileges columm
is null). Default privileges always include all privileges for the owner,
and may include some privileges for <literal>PUBLIC</> depending on the
object type, as explained above. The first <command>GRANT</> or
<command>REVOKE</> on an object
......@@ -325,7 +326,7 @@ will instantiate the default privileges (producing, for example,
<title>Examples</title>
<para>
Grant insert privilege to all users on table films:
Grant insert privilege to all users on table <literal>films</literal>:
<programlisting>
GRANT INSERT ON films TO PUBLIC;
......@@ -344,37 +345,35 @@ GRANT ALL PRIVILEGES ON kinds TO manuel;
<refsect1 id="sql-grant-compatibility">
<title>Compatibility</title>
<refsect2>
<title>SQL92</title>
<para>
The <literal>PRIVILEGES</literal> key word in <literal>ALL
PRIVILEGES</literal> is required. <acronym>SQL</acronym> does not
support setting the privileges on more than one table per command.
According to the SQL standard, the <literal>PRIVILEGES</literal>
key word in <literal>ALL PRIVILEGES</literal> is required. The
SQL standard does not support setting the privileges on more than
one object per command.
</para>
<para>
The <acronym>SQL</acronym> syntax for <literal>GRANT</literal>
allows setting privileges for individual columns within a table:
The SQL standard allows setting privileges for individual columns
within a table:
<synopsis>
GRANT <replaceable class="PARAMETER">privilege</replaceable> [, ...]
GRANT <replaceable class="PARAMETER">privileges</replaceable>
ON <replaceable class="PARAMETER">table</replaceable> [ ( <replaceable class="PARAMETER">column</replaceable> [, ...] ) ] [, ...]
TO { PUBLIC | <replaceable class="PARAMETER">username</replaceable> [, ...] } [ WITH GRANT OPTION ]
</synopsis>
</para>
<para>
<acronym>SQL</acronym> allows to grant the USAGE privilege on
other kinds of objects: CHARACTER SET, COLLATION, TRANSLATION, DOMAIN.
The SQL standard provides for a <literal>USAGE</literal> privilege
on other kinds of objects: character sets, collations,
translations, domains.
</para>
<para>
The TRIGGER privilege was introduced in SQL99. The RULE privilege
is a PostgreSQL extension.
The <literal>RULE</literal> privilege, and privileges on
databases, schemas, languages, and sequences are PostgreSQL
extensions.
</para>
</refsect2>
</refsect1>
......
doc/src/sgml/ref/insert.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/insert.sgml,v 1.21 2003/03/25 16:15:42 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/insert.sgml,v 1.22 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,29 +8,51 @@ PostgreSQL documentation
<refentrytitle id="SQL-INSERT-TITLE">INSERT</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
INSERT
</refname>
<refpurpose>
create new rows in a table
</refpurpose>
<refname>INSERT</refname>
<refpurpose>create new rows in a table</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>2000-08-08</date>
</refsynopsisdivinfo>
<synopsis>
<synopsis>
INSERT INTO <replaceable class="PARAMETER">table</replaceable> [ ( <replaceable class="PARAMETER">column</replaceable> [, ...] ) ]
{ DEFAULT VALUES | VALUES ( { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...] ) | SELECT <replaceable class="PARAMETER">query</replaceable> }
</synopsis>
{ DEFAULT VALUES | VALUES ( { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...] ) | <replaceable class="PARAMETER">query</replaceable> }
</synopsis>
</refsynopsisdiv>
<refsect2 id="R2-SQL-INSERT-1">
<title>
Inputs
</title>
<refsect1>
<title>Description</title>
<para>
<command>INSERT</command> allows one to insert new rows into a
table. One can insert
a single row at a time or several rows as a result of a query.
</para>
<para>
The columns in the target list may be listed in any order.
Each column not present in the target list will be inserted
using a default value, either a declared default value
or null.
</para>
<para>
If the expression for each column is not of the correct data type,
automatic type conversion will be attempted.
</para>
<para>
You must have <literal>INSERT</literal> privilege to a table in
order to insert into it. If you use the <replaceable
class="PARAMETER">query</replaceable> clause to insert rows from a
query, you also need to have <literal>SELECT</literal> privilege on
any table used in the query.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
......@@ -52,11 +74,10 @@ INSERT INTO <replaceable class="PARAMETER">table</replaceable> [ ( <replaceable
</varlistentry>
<varlistentry>
<term>DEFAULT VALUES</term>
<term><literal>DEFAULT VALUES</literal></term>
<listitem>
<para>
All columns will be filled by null values or by values specified
when the table was created using <literal>DEFAULT</> clauses.
All columns will be filled their default values.
</para>
</listitem>
</varlistentry>
......@@ -65,18 +86,17 @@ INSERT INTO <replaceable class="PARAMETER">table</replaceable> [ ( <replaceable
<term><replaceable class="PARAMETER">expression</replaceable></term>
<listitem>
<para>
A valid expression or value to assign to <replaceable
An expression or value to assign to <replaceable
class="PARAMETER">column</replaceable>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">DEFAULT</replaceable></term>
<term><literal>DEFAULT</literal></term>
<listitem>
<para>
This column will be filled in by the column DEFAULT clause, or NULL if
a default is not available.
This column will be filled with its default value.
</para>
</listitem>
</varlistentry>
......@@ -85,169 +105,110 @@ INSERT INTO <replaceable class="PARAMETER">table</replaceable> [ ( <replaceable
<term><replaceable class="PARAMETER">query</replaceable></term>
<listitem>
<para>
A valid query. Refer to the SELECT statement for a further description
of valid arguments.
A query (<command>SELECT</command> statement) that supplies the
rows to be inserted. Refer to the <command>SELECT</command>
statement for a description of the syntax.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsect1>
<refsect2 id="R2-SQL-INSERT-2">
<title>
Outputs
</title>
<para>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>
INSERT <replaceable>oid</replaceable> 1
</computeroutput></term>
<term><computeroutput>INSERT <replaceable>oid</replaceable> 1</computeroutput></term>
<listitem>
<para>
Message returned if only one row was inserted.
<returnvalue><replaceable>oid</replaceable></returnvalue>
is the numeric <acronym>OID</acronym> of the inserted row.
<returnvalue><replaceable>oid</replaceable></returnvalue> is the
<acronym>OID</acronym> of the inserted row.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><computeroutput>
INSERT 0 <replaceable>#</replaceable>
</computeroutput></term>
<term><computeroutput>INSERT 0 <replaceable>count</replaceable></computeroutput></term>
<listitem>
<para>
Message returned if more than one rows were inserted.
<returnvalue><replaceable>#</replaceable></returnvalue>
is the number of rows inserted.
<replaceable>count</replaceable> is the number of rows inserted.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-INSERT-1">
<title>
Description
</title>
<para>
<command>INSERT</command> allows one to insert new rows into a
table. One can insert
a single row at a time or several rows as a result of a query.
The columns in the target list may be listed in any order.
</para>
<para>
Each column not present in the target list will be inserted
using a default value, either a declared DEFAULT value
or NULL. <productname>PostgreSQL</productname> will reject the new
column if a NULL is inserted into a column declared NOT NULL.
</para>
<para>
If the expression for each column
is not of the correct data type, automatic type coercion will be
attempted.
</para>
<para>
You must have insert privilege to a table in order to append
to it, as well as select privilege on any table specified
in a WHERE clause.
</para>
</refsect1>
<refsect1 id="R1-SQL-INSERT-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
Insert a single row into table <literal>films</literal>:
<programlisting>
<programlisting>
INSERT INTO films VALUES
('UA502','Bananas',105,'1971-07-13','Comedy',INTERVAL '82 minute');
</programlisting>
('UA502', 'Bananas', 105, '1971-07-13', 'Comedy', '82 minutes');
</programlisting>
</para>
<para>
In this second example the last column <literal>len</literal> is
omitted and therefore it will have the default value of NULL:
In this second example, the last column <literal>len</literal> is
omitted and therefore it will have the default value of null:
<programlisting>
<programlisting>
INSERT INTO films (code, title, did, date_prod, kind)
VALUES ('T_601', 'Yojimbo', 106, DATE '1961-06-16', 'Drama');
</programlisting>
VALUES ('T_601', 'Yojimbo', 106, '1961-06-16', 'Drama');
</programlisting>
</para>
<para>
In the third example, we use the DEFAULT values for the date columns
rather than specifying an entry.
The third example uses the <literal>DEFAULT</literal> clause for
the date columns rather than specifying a value:
<programlisting>
<programlisting>
INSERT INTO films VALUES
('UA502','Bananas',105,DEFAULT,'Comedy',INTERVAL '82 minute');
('UA502', 'Bananas', 105, DEFAULT, 'Comedy', '82 minutes');
INSERT INTO films (code, title, did, date_prod, kind)
VALUES ('T_601', 'Yojimbo', 106, DEFAULT, 'Drama');
</programlisting>
</para>
<para>
Insert a single row into table distributors; note that
only column <literal>name</literal> is specified, so the omitted
column <literal>did</literal> will be assigned its default value:
<programlisting>
INSERT INTO distributors (name) VALUES ('British Lion');
</programlisting>
</programlisting>
</para>
<para>
Insert several rows into table films from table <literal>tmp</literal>:
This examples inserts several rows into table
<literal>films</literal> from table <literal>tmp</literal>:
<programlisting>
<programlisting>
INSERT INTO films SELECT * FROM tmp;
</programlisting>
</programlisting>
</para>
<para>
Insert into arrays:
This example inserts into array columns:
<programlisting>
<programlisting>
-- Create an empty 3x3 gameboard for noughts-and-crosses
-- (all of these queries create the same board attribute)
-- (all of these commands create the same board)
INSERT INTO tictactoe (game, board[1:3][1:3])
VALUES (1,'{{"","",""},{},{"",""}}');
INSERT INTO tictactoe (game, board[3][3])
VALUES (2,'{}');
INSERT INTO tictactoe (game, board)
VALUES (3,'{{,,},{,,},{,,}}');
</programlisting>
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-INSERT-3">
<title>
Compatibility
</title>
<refsect1>
<title>Compatibility</title>
<refsect2 id="R2-SQL-INSERT-4">
<title>
SQL92
</title>
<para>
<command>INSERT</command> is fully compatible with <acronym>SQL92</acronym>.
Possible limitations in features of the
<replaceable class="PARAMETER">query</replaceable>
clause are documented for
<command>INSERT</command> conforms fully to the SQL standard.
Possible limitations of the <replaceable
class="PARAMETER">query</replaceable> clause are documented under
<xref linkend="sql-select" endterm="sql-select-title">.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/listen.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/listen.sgml,v 1.15 2002/09/21 18:32:54 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/listen.sgml,v 1.16 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,121 +8,54 @@ PostgreSQL documentation
<refentrytitle id="SQL-LISTEN-TITLE">LISTEN</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
LISTEN
</refname>
<refpurpose>
listen for a notification
</refpurpose>
<refname>LISTEN</refname>
<refpurpose>listen for a notification</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1999-07-20</date>
</refsynopsisdivinfo>
<synopsis>
<synopsis>
LISTEN <replaceable class="PARAMETER">name</replaceable>
</synopsis>
<refsect2 id="R2-SQL-LISTEN-1">
<refsect2info>
<date>1998-10-07</date>
</refsect2info>
<title>
Inputs
</title>
<para>
<variablelist>
<varlistentry>
<term><replaceable class="PARAMETER">name</replaceable></term>
<listitem>
<para>
Name of notify condition.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="R2-SQL-LISTEN-2">
<refsect2info>
<date>1998-09-24</date>
</refsect2info>
<title>
Outputs
</title>
<para>
<variablelist>
<varlistentry>
<term><computeroutput>
LISTEN
</computeroutput></term>
<listitem>
<para>
Message returned upon successful completion of registration.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><computeroutput>
WARNING: Async_Listen: We are already listening on <replaceable class="PARAMETER">name</replaceable>
</computeroutput></term>
<listitem>
<para>
If this backend is already registered for that notify condition.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</synopsis>
</refsynopsisdiv>
<refsect1 id="R1-SQL-LISTEN-1">
<refsect1info>
<date>1998-10-07</date>
</refsect1info>
<title>
Description
</title>
<refsect1>
<title>Description</title>
<para>
<command>LISTEN</command> registers the current
<productname>PostgreSQL</productname> backend as a
listener on the notify condition
<replaceable class="PARAMETER">name</replaceable>.
<command>LISTEN</command> registers the current session as a
listener on the notification condition <replaceable
class="PARAMETER">name</replaceable>.
</para>
<para>
Whenever the command
<command>NOTIFY <replaceable class="PARAMETER">name</replaceable></command>
is invoked, either by this backend or another one connected to
the same database, all the backends currently listening on that notify
condition are notified, and each will in turn notify its connected
frontend application. See the discussion of <command>NOTIFY</command>
for more information.
Whenever the command <command>NOTIFY <replaceable
class="PARAMETER">name</replaceable></command> is invoked, either
by this session or another one connected to the same database, all
the sessions currently listening on that notification condition are
notified, and each will in turn notify its connected client
application. See the discussion of <command>NOTIFY</command> for
more information.
</para>
<para>
A backend can be unregistered for a given notify condition with the
<command>UNLISTEN</command> command. Also, a backend's listen registrations
are automatically cleared when the backend process exits.
A session can be unregistered for a given notify condition with the
<command>UNLISTEN</command> command. A session's listen
registrations are automatically cleared when the session ends.
</para>
<para>
The method a frontend application must use to detect notify events depends on
The method a client application must use to detect notification events depends on
which <productname>PostgreSQL</productname> application programming interface it
uses. With the <application>libpq</> library, the application issues
<command>LISTEN</command> as an ordinary SQL command, and then must
periodically call the routine <function>PQnotifies</function> to find out
whether any notify events have been received. Other interfaces such as
periodically call the function <function>PQnotifies</function> to find out
whether any notification events have been received. Other interfaces such as
<application>libpgtcl</> provide higher-level methods for handling notify events; indeed,
with <application>libpgtcl</> the application programmer should not even issue
<command>LISTEN</command> or <command>UNLISTEN</command> directly. See the
documentation for the library you are using for more details.
documentation for the interface you are using for more details.
</para>
<para>
......@@ -131,64 +64,67 @@ WARNING: Async_Listen: We are already listening on <replaceable class="PARAMETE
discussion of the use of <command>LISTEN</command> and
<command>NOTIFY</command>.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="PARAMETER">name</replaceable></term>
<listitem>
<para>
Name of a notify condition (any identifier).
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect2 id="R2-SQL-LISTEN-3">
<refsect2info>
<date>1998-10-07</date>
</refsect2info>
<title>
Notes
</title>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>LISTEN</computeroutput></term>
<listitem>
<para>
<replaceable class="PARAMETER">name</replaceable>
can be any string valid as a name;
it need not correspond to the name of any actual table. If
<replaceable class="PARAMETER">notifyname</replaceable>
is enclosed in double-quotes, it need not even be a syntactically
valid name, but can be any string up to 63 characters long.
Message returned upon successful completion of registration.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><computeroutput>WARNING: Async_Listen: We are already listening on <replaceable class="PARAMETER">name</replaceable></computeroutput></term>
<listitem>
<para>
In some previous releases of
<productname>PostgreSQL</productname>,
<replaceable class="PARAMETER">name</replaceable>
had to be enclosed in double-quotes when it did not correspond to any existing
table name, even if syntactically valid as a name. That is no longer required.
Message returned if this session is already registered for that notification condition.
</para>
</refsect2>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="R1-SQL-LISTEN-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
Configure and execute a listen/notify sequence from <application>psql</application>:
<programlisting>
LISTEN virtual;
NOTIFY virtual;
Asynchronous NOTIFY 'virtual' from backend with pid '8448' received.
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-LISTEN-3">
<title>
Compatibility
</title>
<refsect2 id="R2-SQL-LISTEN-4">
<refsect2info>
<date>1998-09-01</date>
</refsect2info>
<title>
SQL92
</title>
<refsect1>
<title>Compatibility</title>
<para>
There is no <command>LISTEN</command> in <acronym>SQL92</acronym>.
There is no <command>LISTEN</command> statement in the SQL
standard.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/load.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/load.sgml,v 1.16 2003/03/25 16:15:42 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/load.sgml,v 1.17 2003/04/26 23:56:51 petere Exp $
-->
<refentry id="SQL-LOAD">
......@@ -23,11 +23,11 @@ LOAD '<replaceable class="PARAMETER">filename</replaceable>'
<title>Description</title>
<para>
Loads a shared library file into the <productname>PostgreSQL</>
backend's address space. If the file had been loaded previously,
This command loads a shared library file into the <productname>PostgreSQL</>
server's address space. If the file had been loaded previously,
it is first unloaded. This command is primarily useful to unload
and reload a shared library file that has been changed since the
backend first loaded it. To make use of the shared library,
server first loaded it. To make use of the shared library,
function(s) in it need to be declared using the <xref
linkend="sql-createfunction" endterm="sql-createfunction-title">
command.
......
doc/src/sgml/ref/lock.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/lock.sgml,v 1.34 2002/09/21 18:32:54 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/lock.sgml,v 1.35 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,364 +8,143 @@ PostgreSQL documentation
<refentrytitle id="sql-lock-title">LOCK</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
LOCK
</refname>
<refpurpose>
explicitly lock a table
</refpurpose>
<refname>LOCK</refname>
<refpurpose>lock a table</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>2001-07-09</date>
</refsynopsisdivinfo>
<synopsis>
LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...]
LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...] IN <replaceable class="PARAMETER">lockmode</replaceable> MODE
<synopsis>
LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ IN <replaceable class="PARAMETER">lockmode</replaceable> MODE ]
where <replaceable class="PARAMETER">lockmode</replaceable> is one of:
ACCESS SHARE | ROW SHARE | ROW EXCLUSIVE | SHARE UPDATE EXCLUSIVE |
SHARE | SHARE ROW EXCLUSIVE | EXCLUSIVE | ACCESS EXCLUSIVE
</synopsis>
<refsect2 id="R2-SQL-LOCK-1">
<refsect2info>
<date>1999-06-09</date>
</refsect2info>
<title>
Inputs
</title>
<para>
<variablelist>
<varlistentry>
<term><replaceable class="PARAMETER">name</replaceable></term>
<listitem>
<para>
The name (optionally schema-qualified) of an existing table to lock.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>ACCESS SHARE MODE</term>
<listitem>
<para>
This is the least restrictive lock mode. It conflicts only with
ACCESS EXCLUSIVE mode. It is used to protect a table from being
modified by concurrent <command>ALTER TABLE</command>,
<command>DROP TABLE</command> and <command>VACUUM FULL</command>
commands.
</para>
<note>
<para>
The <command>SELECT</command> command acquires a
lock of this mode on referenced tables. In general, any query
that only reads a table and does not modify it will acquire
this lock mode.
</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term>ROW SHARE MODE</term>
<listitem>
<para>
Conflicts with EXCLUSIVE and ACCESS EXCLUSIVE lock modes.
</para>
<note>
<para>
The <command>SELECT FOR UPDATE</command> command acquires a
lock of this mode on the target table(s) (in addition to
<literal>ACCESS SHARE</literal> locks on any other tables
that are referenced but not selected <option>FOR UPDATE</option>).
</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term>ROW EXCLUSIVE MODE</term>
<listitem>
<para>
Conflicts with SHARE, SHARE ROW EXCLUSIVE, EXCLUSIVE and
ACCESS EXCLUSIVE modes.
</para>
ACCESS SHARE | ROW SHARE | ROW EXCLUSIVE | SHARE UPDATE EXCLUSIVE
| SHARE | SHARE ROW EXCLUSIVE | EXCLUSIVE | ACCESS EXCLUSIVE
</synopsis>
</refsynopsisdiv>
<note>
<para>
The commands <command>UPDATE</command>,
<command>DELETE</command>, and <command>INSERT</command>
acquire this lock mode on the target table (in addition to
<literal>ACCESS SHARE</literal> locks on any other referenced
tables). In general, this lock mode will be acquired by any
query that modifies the data in a table.
</para>
</note>
</listitem>
</varlistentry>
<refsect1>
<title>Description</title>
<varlistentry>
<term>SHARE UPDATE EXCLUSIVE MODE</term>
<listitem>
<para>
Conflicts with SHARE UPDATE EXCLUSIVE, SHARE, SHARE ROW EXCLUSIVE,
EXCLUSIVE and
ACCESS EXCLUSIVE modes. This mode protects a table against
concurrent schema changes and <command>VACUUM</> runs.
<command>LOCK TABLE</command> obtains a table-level lock, waiting if
necessary for any conflicting locks to be released. Once obtained,
the lock is held for the remainder of the current transaction.
(There is no <command>UNLOCK TABLE</command> command; locks are always
released at transaction end.)
</para>
<note>
<para>
Acquired by <command>VACUUM</command> (without
<option>FULL</option>).
When acquiring locks automatically for commands that reference
tables, <productname>PostgreSQL</productname> always uses the least
restrictive lock mode possible. <command>LOCK TABLE</command>
provides for cases when you might need more restrictive locking.
For example, suppose an application runs a transaction at the
isolation level read committed and needs to ensure that data in a
table remains stable for the duration of the transaction. To
achieve this you could obtain <literal>SHARE</> lock mode over the
table before querying. This will prevent concurrent data changes
and ensure subsequent reads of the table see a stable view of
committed data, because <literal>SHARE</> lock mode conflicts with
the <literal>ROW EXCLUSIVE</> lock acquired by writers, and your
<command>LOCK TABLE <replaceable
class="PARAMETER">name</replaceable> IN SHARE MODE</command>
statement will wait until any concurrent holders of <literal>ROW
EXCLUSIVE</literal> mode locks commit or roll back. Thus, once you
obtain the lock, there are no uncommitted writes outstanding;
furthermore none can begin until you release the lock.
</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term>SHARE MODE</term>
<listitem>
<para>
Conflicts with ROW EXCLUSIVE, SHARE UPDATE EXCLUSIVE,
SHARE ROW EXCLUSIVE, EXCLUSIVE and
ACCESS EXCLUSIVE modes. This mode protects a table against
concurrent data changes.
To achieve a similar effect when running a transaction at the
isolation level serializable, you have to execute the <command>LOCK
TABLE</> statement before executing any data modification
statement. A serializable transaction's view of data will be
frozen when its first data modification statement begins. A later
<command>LOCK TABLE</> will still prevent concurrent writes --- but it
won't ensure that what the transaction reads corresponds to the
latest committed values.
</para>
<note>
<para>
Acquired by <command>CREATE INDEX</command>.
If a transaction of this sort is going to change the data in the
table, then it should use <literal>SHARE ROW EXCLUSIVE</> lock mode
instead of <literal>SHARE</> mode. This ensures that only one
transaction of this type runs at a time. Without this, a deadlock
is possible: two transactions might both acquire <literal>SHARE</>
mode, and then be unable to also acquire <literal>ROW EXCLUSIVE</>
mode to actually perform their updates. (Note that a transaction's
own locks never conflict, so a transaction can acquire <literal>ROW
EXCLUSIVE</> mode when it holds <literal>SHARE</> mode --- but not
if anyone else holds <literal>SHARE</> mode.) To avoid deadlocks,
make sure all transactions acquire locks on the same objects in the
same order, and if multiple lock modes are involved for a single
object, then transactions should always acquire the most
restrictive mode first.
</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term>SHARE ROW EXCLUSIVE MODE</term>
<listitem>
<para>
Conflicts with ROW EXCLUSIVE, SHARE UPDATE EXCLUSIVE, SHARE,
SHARE ROW EXCLUSIVE, EXCLUSIVE and ACCESS EXCLUSIVE modes.
More information about the lock modes and locking strategies can be
found in <xref linkend="explicit-locking">.
</para>
</refsect1>
<note>
<para>
This lock mode is not automatically acquired by any
<productname>PostgreSQL</productname> command.
</para>
</note>
</listitem>
</varlistentry>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term>EXCLUSIVE MODE</term>
<term><replaceable class="PARAMETER">name</replaceable></term>
<listitem>
<para>
Conflicts with ROW SHARE, ROW EXCLUSIVE, SHARE UPDATE EXCLUSIVE,
SHARE, SHARE ROW EXCLUSIVE,
EXCLUSIVE and ACCESS EXCLUSIVE modes.
This mode allows only concurrent ACCESS SHARE, i.e., only reads
from the table can proceed in parallel with a transaction holding
this lock mode.
The name (optionally schema-qualified) of an existing table to
lock.
</para>
<note>
<para>
This lock mode is not automatically acquired by any
<productname>PostgreSQL</productname> command.
The command <literal>LOCK a, b;</> is equivalent to
<literal>LOCK a; LOCK b;</>. The tables are locked one-by-one in
the order specified in the <command>LOCK</command> command.
</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term>ACCESS EXCLUSIVE MODE</term>
<term><replaceable class="parameter">lockmode</replaceable></term>
<listitem>
<para>
Conflicts with all lock modes. This mode guarantees that the
holder is the only transaction accessing the table in any way.
The lock mode specifies which locks this lock conflicts with.
Lock modes are described in <xref linkend="explicit-locking">.
</para>
<note>
<para>
Acquired by <command>ALTER TABLE</command>,
<command>DROP TABLE</command>, and <command>VACUUM FULL</command>
statements.
This is also the default lock mode for <command>LOCK TABLE</command>
statements that do not specify a mode explicitly.
If no lock mode is specified, then <literal>ACCESS
EXCLUSIVE</literal>, the most restrictive mode, is used.
</para>
</note>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsect1>
<refsect2 id="R2-SQL-LOCK-2">
<refsect2info>
<date>1998-09-24</date>
</refsect2info>
<title>
Outputs
</title>
<para>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>
LOCK TABLE
</computeroutput></term>
<listitem>
<para>
The lock was successfully acquired.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><computeroutput>
ERROR <replaceable class="PARAMETER">name</replaceable>: Table does not exist.
</computeroutput></term>
<term><computeroutput>LOCK TABLE</computeroutput></term>
<listitem>
<para>
Message returned if <replaceable class="PARAMETER">name</replaceable>
does not exist.
Message returned if the lock was successfully acquired.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-LOCK-1">
<refsect1info>
<date>1998-09-24</date>
</refsect1info>
<title>
Description
</title>
<para>
<command>LOCK TABLE</command> obtains a table-level lock, waiting if
necessary for any conflicting locks to be released. Once obtained,
the lock is held for the remainder of the current transaction.
(There is no <command>UNLOCK TABLE</command> command; locks are always
released at transaction end.)
</para>
<para>
When acquiring locks automatically for commands that reference tables,
<productname>PostgreSQL</productname> always uses the least restrictive
lock mode possible. <command>LOCK TABLE</command>
provides for cases when you might need more restrictive locking.
</para>
<para>
For example, suppose an application runs a transaction at READ COMMITTED
isolation level and needs to ensure that data in a table remains stable
for the duration of the
transaction. To achieve this you could obtain SHARE lock mode over the
table before querying. This will prevent concurrent data changes
and ensure subsequent reads of the table see a stable
view of committed data, because SHARE lock mode conflicts with the ROW
EXCLUSIVE lock acquired by writers, and your
<command>LOCK TABLE <replaceable class="PARAMETER">name</replaceable> IN SHARE MODE</command>
statement will wait until any concurrent holders of ROW EXCLUSIVE mode
commit or roll back. Thus, once you obtain the lock, there are no
uncommitted writes outstanding; furthermore none can begin until you
release the lock.
<note>
<para>
To achieve a similar effect when running a transaction
at the SERIALIZABLE isolation level, you have to execute the
<command>LOCK TABLE</>
statement before executing any <acronym>DML</> statement. A serializable
transaction's view of data will be frozen when its first <acronym>DML</> statement
begins. A later <command>LOCK</> will still prevent concurrent writes
--- but it
won't ensure that what the transaction reads corresponds to the latest
committed values.
</para>
</note>
</para>
<para>
If a transaction of this sort is going to
change the data in the table, then it should use SHARE ROW EXCLUSIVE lock
mode instead of SHARE mode. This ensures that only one transaction of
this type runs at a time. Without this, a deadlock is possible: two
transactions might both acquire SHARE mode, and then be unable to also
acquire ROW EXCLUSIVE mode to actually perform their updates. (Note that
a transaction's own locks never conflict, so a transaction can acquire
ROW EXCLUSIVE mode when it holds SHARE mode --- but not if anyone else
holds SHARE mode.)
</para>
<para>
Two general rules may be followed to prevent deadlock conditions:
</para>
<itemizedlist>
<listitem>
<para>
Transactions have to acquire locks on the same objects in the same order.
</para>
<para>
For example, if one application updates row R1 and than updates
row R2 (in the same transaction) then the second application shouldn't
update row R2 if it's going to update row R1 later (in a single transaction).
Instead, it should update rows R1 and R2 in the same order as the first
application.
</para>
</listitem>
<listitem>
<para>
If multiple lock modes are involved for a single object,
then transactions should always acquire the most restrictive mode first.
</para>
<para>
An example for this rule was given previously when discussing the
use of SHARE ROW EXCLUSIVE mode rather than SHARE mode.
</para>
</listitem>
</itemizedlist>
<para>
<productname>PostgreSQL</productname> does detect deadlocks and will
rollback at least one waiting transaction to resolve the deadlock.
If it is not practical to code an application to follow the above rules
strictly, an alternative solution is to be prepared to retry transactions
when they are aborted by deadlocks.
</para>
<para>
When locking multiple tables, the command <literal>LOCK a, b;</> is
equivalent to <literal>LOCK a; LOCK b;</>. The tables are locked one-by-one
in the order specified in the
<command>LOCK</command> command.
</para>
</refsect1>
<refsect2 id="R2-SQL-LOCK-3">
<refsect2info>
<date>1999-06-08</date>
</refsect2info>
<title>
Notes
</title>
<refsect1>
<title>Notes</title>
<para>
<literal>LOCK ... IN ACCESS SHARE MODE</> requires <literal>SELECT</>
......@@ -375,81 +154,32 @@ ERROR <replaceable class="PARAMETER">name</replaceable>: Table does not exist.
<para>
<command>LOCK</command> is useful only inside a transaction block
(<command>BEGIN</>...<command>COMMIT</>), since the lock is dropped
(<command>BEGIN</>/<command>COMMIT</> pair), since the lock is dropped
as soon as the transaction ends. A <command>LOCK</> command appearing
outside any transaction block forms a self-contained transaction, so the
lock will be dropped as soon as it is obtained.
</para>
<para>
<acronym>RDBMS</acronym> locking uses the following standard terminology:
<variablelist>
<varlistentry>
<term>EXCLUSIVE</term>
<listitem>
<para>
An exclusive lock prevents other locks of the same type from being
granted.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>SHARE</term>
<listitem>
<para>
A shared lock allows others to also hold the same type of lock,
but prevents the corresponding EXCLUSIVE lock from being granted.
<command>LOCK TABLE</> only deals with table-level locks, and so
the mode names involving <literal>ROW</> are all misnomers. These
mode names should generally be read as indicating the intention of
the user to acquire row-level locks within the locked table. Also,
<literal>ROW EXCLUSIVE</> mode is a sharable table lock. Keep in
mind that all the lock modes have identical semantics so far as
<command>LOCK TABLE</> is concerned, differing only in the rules
about which modes conflict with which.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>ACCESS</term>
<listitem>
<para>
Locks table schema.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>ROW</term>
<listitem>
<para>
Locks individual rows.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
<productname>PostgreSQL</productname> does not follow this terminology
exactly. <command>LOCK TABLE</> only deals with table-level locks, and
so the mode names involving ROW are all misnomers. These mode names
should generally be read as indicating the intention of the user to
acquire row-level locks within the locked table. Also,
ROW EXCLUSIVE mode does not follow this naming convention accurately,
since it is a sharable table lock. Keep in mind that all the lock modes
have identical semantics so far as <command>LOCK TABLE</> is concerned,
differing only in the rules about which modes conflict with which.
</para>
</refsect2>
</refsect1>
<refsect1 id="R1-SQL-LOCK-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
Obtain a SHARE lock on a primary key table when going to perform
Obtain a <literal>SHARE</> lock on a primary key table when going to perform
inserts into a foreign key table:
<programlisting>
<programlisting>
BEGIN WORK;
LOCK TABLE films IN SHARE MODE;
SELECT id FROM films
......@@ -458,50 +188,42 @@ SELECT id FROM films
INSERT INTO films_user_comments VALUES
(_id_, 'GREAT! I was waiting for it for so long!');
COMMIT WORK;
</programlisting>
</programlisting>
</para>
<para>
Take a SHARE ROW EXCLUSIVE lock on a primary key table when going to perform
Take a <literal>SHARE ROW EXCLUSIVE</> lock on a primary key table when going to perform
a delete operation:
<programlisting>
<programlisting>
BEGIN WORK;
LOCK TABLE films IN SHARE ROW EXCLUSIVE MODE;
DELETE FROM films_user_comments WHERE id IN
(SELECT id FROM films WHERE rating < 5);
DELETE FROM films WHERE rating < 5;
COMMIT WORK;
</programlisting>
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-LOCK-3">
<title>
Compatibility
</title>
<refsect1>
<title>Compatibility</title>
<refsect2 id="R2-SQL-LOCK-4">
<refsect2info>
<date>1998-09-24</date>
</refsect2info>
<title>
SQL92
</title>
<para>
There is no <command>LOCK TABLE</command> in <acronym>SQL92</acronym>,
There is no <command>LOCK TABLE</command> in the SQL standard,
which instead uses <command>SET TRANSACTION</command> to specify
concurrency levels on transactions. We support that too; see
<xref linkend="SQL-SET-TRANSACTION" endterm="SQL-SET-TRANSACTION-TITLE"> for details.
concurrency levels on transactions. PostgreSQL supports that too;
see <xref linkend="SQL-SET-TRANSACTION"
endterm="SQL-SET-TRANSACTION-TITLE"> for details.
</para>
<para>
Except for ACCESS SHARE, ACCESS EXCLUSIVE, and SHARE UPDATE EXCLUSIVE lock
modes, the <productname>PostgreSQL</productname> lock modes and the
Except for <literal>ACCESS SHARE</>, <literal>ACCESS EXCLUSIVE</>,
and <literal>SHARE UPDATE EXCLUSIVE</> lock modes, the
<productname>PostgreSQL</productname> lock modes and the
<command>LOCK TABLE</command> syntax are compatible with those
present in <productname>Oracle</productname>(TM).
present in <productname>Oracle</productname>.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/notify.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/notify.sgml,v 1.19 2002/09/21 18:32:54 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/notify.sgml,v 1.20 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,113 +8,53 @@ PostgreSQL documentation
<refentrytitle id="sql-notify-title">NOTIFY</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
NOTIFY
</refname>
<refpurpose>
generate a notification
</refpurpose>
<refname>NOTIFY</refname>
<refpurpose>generate a notification</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1999-07-20</date>
</refsynopsisdivinfo>
<synopsis>
<synopsis>
NOTIFY <replaceable class="PARAMETER">name</replaceable>
</synopsis>
<refsect2 id="R2-SQL-NOTIFY-1">
<refsect2info>
<date>1998-10-07</date>
</refsect2info>
<title>
Inputs
</title>
<para>
</synopsis>
</refsynopsisdiv>
<variablelist>
<varlistentry>
<term><replaceable class="PARAMETER">notifyname</replaceable></term>
<listitem>
<para>
Notify condition to be signaled.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="R2-SQL-NOTIFY-2">
<refsect2info>
<date>1998-10-07</date>
</refsect2info>
<title>
Outputs
</title>
<para>
<refsect1>
<title>Description</title>
<variablelist>
<varlistentry>
<term><computeroutput>
NOTIFY
</computeroutput></term>
<listitem>
<para>
Acknowledgement that notify command has executed.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>Notify events</replaceable></term>
<listitem>
<para>
Events are delivered to listening frontends; whether and how each frontend
application reacts depends on its programming.
The <command>NOTIFY</command> command sends a notification event to each
client application that has previously executed
<command>LISTEN <replaceable class="parameter">name</replaceable></command>
for the specified notification name in the current database.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-NOTIFY-1">
<refsect1info>
<date>1998-10-07</date>
</refsect1info>
<title>
Description
</title>
<para>
The <command>NOTIFY</command> command sends a notify event to each
frontend application that has previously executed
<command>LISTEN <replaceable class="parameter">notifyname</replaceable></command>
for the specified notify condition in the current database.
</para>
<para>
The information passed to the frontend for a notify event includes the notify
condition name and the notifying backend process's <acronym>PID</>. It is up to the
database designer to define the condition names that will be used in a given
The information passed to the client for a notifiation event includes the notification
name and the notifying session's server process <acronym>PID</>. It is up to the
database designer to define the notification names that will be used in a given
database and what each one means.
</para>
<para>
Commonly, the notify condition name is the same as the name of some table in
the database, and the notify event essentially means <quote>I changed this table,
Commonly, the notification name is the same as the name of some table in
the database, and the notify event essentially means, <quote>I changed this table,
take a look at it to see what's new</quote>. But no such association is enforced by
the <command>NOTIFY</command> and <command>LISTEN</command> commands. For
example, a database designer could use several different condition names
example, a database designer could use several different notification names
to signal different sorts of changes to a single table.
</para>
<para>
<command>NOTIFY</command> provides a simple form of signal or
<acronym>IPC</> (interprocess communication) mechanism for a collection of processes
interprocess communication mechanism for a collection of processes
accessing the same <productname>PostgreSQL</productname> database.
Higher-level mechanisms can be built by using tables in the database to
pass additional data (beyond a mere condition name) from notifier to
pass additional data (beyond a mere notification name) from notifier to
listener(s).
</para>
<para>
When <command>NOTIFY</command> is used to signal the occurrence of changes
to a particular table, a useful programming technique is to put the
......@@ -122,86 +62,91 @@ NOTIFY
In this way, notification happens automatically when the table is changed,
and the application programmer can't accidentally forget to do it.
</para>
<para>
<command>NOTIFY</command> interacts with SQL transactions in some important
ways. Firstly, if a <command>NOTIFY</command> is executed inside a
transaction, the notify events are not delivered until and unless the
transaction is committed. This is appropriate, since if the transaction
is aborted we would like all the commands within it to have had no
is aborted, all the commands within it have had no
effect, including <command>NOTIFY</command>. But it can be disconcerting if one
is expecting the notify events to be delivered immediately. Secondly, if
a listening backend receives a notify signal while it is within a transaction,
the notify event will not be delivered to its connected frontend until just
is expecting the notification events to be delivered immediately. Secondly, if
a listening session receives a notification signal while it is within a transaction,
the notification event will not be delivered to its connected client until just
after the transaction is completed (either committed or aborted). Again, the
reasoning is that if a notify were delivered within a transaction that was
reasoning is that if a notification were delivered within a transaction that was
later aborted, one would want the notification to be undone somehow---but
the backend cannot <quote>take back</quote> a notify once it has sent it to the frontend.
So notify events are only delivered between transactions. The upshot of this
the server cannot <quote>take back</quote> a notification once it has sent it to the client.
So notification events are only delivered between transactions. The upshot of this
is that applications using <command>NOTIFY</command> for real-time signaling
should try to keep their transactions short.
</para>
<para>
<command>NOTIFY</command> behaves like Unix signals in one important
respect: if the same condition name is signaled multiple times in quick
succession, recipients may get only one notify event for several executions
respect: if the same notification name is signaled multiple times in quick
succession, recipients may get only one notification event for several executions
of <command>NOTIFY</command>. So it is a bad idea to depend on the number
of notifies received. Instead, use <command>NOTIFY</command> to wake up
of notifications received. Instead, use <command>NOTIFY</command> to wake up
applications that need to pay attention to something, and use a database
object (such as a sequence) to keep track of what happened or how many times
it happened.
</para>
<para>
It is common for a frontend that sends <command>NOTIFY</command> to be
listening on the same notify name itself. In that case it will get back a
notify event, just like all the other listening frontends. Depending on the
application logic, this could result in useless work---for example,
re-reading a database table to find the same updates that that frontend just
wrote out. In <productname>PostgreSQL</productname> 6.4 and later, it is
possible to avoid such extra work by noticing whether the notifying backend
process's <acronym>PID</> (supplied in the notify event message) is the same as one's own
backend's <acronym>PID</> (available from <application>libpq</>). When they are the same, the notify
event is one's own work bouncing back, and can be ignored. (Despite what was
said in the preceding paragraph, this is a safe technique.
<productname>PostgreSQL</productname> keeps self-notifies separate from notifies
arriving from other backends, so you cannot miss an outside notify by ignoring
your own notifies.)
</para>
<refsect2 id="R2-SQL-NOTIFY-3">
<refsect2info>
<date>1998-10-07</date>
</refsect2info>
<title>
Notes
</title>
<para>
<replaceable class="PARAMETER">name</replaceable>
can be any string valid as a name;
it need not correspond to the name of any actual table. If
<replaceable class="PARAMETER">name</replaceable>
is enclosed in double-quotes, it need not even be a syntactically
valid name, but can be any string up to 63 characters long.
It is common for a client that executes <command>NOTIFY</command>
to be listening on the same notification name itself. In that case
it will get back a notification event, just like all the other
listening sessions. Depending on the application logic, this could
result in useless work, for example, reading a database table to
find the same updates that that session just wrote out. It is
possible to avoid such extra work by noticing whether the notifying
session's server process <acronym>PID</> (supplied in the
notification event message) is the same as one's own session's
<acronym>PID</> (available from <application>libpq</>). When they
are the same, the notification event is one's own work bouncing
back, and can be ignored. (Despite what was said in the preceding
paragraph, this is a safe technique.
<productname>PostgreSQL</productname> keeps self-notifiications
separate from notifications arriving from other sessions, so you
cannot miss an outside notification by ignoring your own
notifications.)
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="PARAMETER">name</replaceable></term>
<listitem>
<para>
In some previous releases of
<productname>PostgreSQL</productname>,
<replaceable class="PARAMETER">name</replaceable>
had to be enclosed in double-quotes when it did not correspond to any existing
table name, even if syntactically valid as a name. That is no longer required.
Name of the notification to be signaled (any identifier).
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>NOTIFY</computeroutput></term>
<listitem>
<para>
In <productname>PostgreSQL</productname> releases prior to 6.4, the backend
<acronym>PID</> delivered in a notify message was always the <acronym>PID</> of the frontend's own
backend. So it was not possible to distinguish one's own notifies from other
clients' notifies in those earlier releases.
Message returned when the commmand has executed.
</para>
</refsect2>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="R1-SQL-NOTIFY-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
Configure and execute a listen/notify sequence from
<application>psql</application>:
......@@ -214,23 +159,13 @@ Asynchronous NOTIFY 'virtual' from backend with pid '8448' received.
</para>
</refsect1>
<refsect1 id="R1-SQL-NOTIFY-3">
<title>
Compatibility
</title>
<refsect2 id="R2-SQL-NOTIFY-4">
<refsect2info>
<date>1998-09-24</date>
</refsect2info>
<title>
SQL92
</title>
<refsect1>
<title>Compatibility</title>
<para>
There is no <command>NOTIFY</command> statement in
<acronym>SQL92</acronym>.
There is no <command>NOTIFY</command> statement in the SQL
standard.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/prepare.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/prepare.sgml,v 1.3 2003/03/10 03:53:49 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/prepare.sgml,v 1.4 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,197 +8,158 @@ PostgreSQL documentation
<refentrytitle id="sql-prepare-title">PREPARE</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
PREPARE
</refname>
<refpurpose>
create a prepared query
</refpurpose>
<refname>PREPARE</refname>
<refpurpose>prepare a statement for execution</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>2002-08-12</date>
</refsynopsisdivinfo>
<synopsis>
PREPARE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable class="PARAMETER">datatype</replaceable> [, ...] ) ] AS <replaceable class="PARAMETER">query</replaceable>
</synopsis>
<refsect2 id="R2-SQL-PREPARE-1">
<refsect2info>
<date>2002-08-12</date>
</refsect2info>
<title>
Inputs
</title>
<synopsis>
PREPARE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable class="PARAMETER">datatype</replaceable> [, ...] ) ] AS <replaceable class="PARAMETER">statement</replaceable>
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>PREPARE</command> creates a prepared statement. A prepared
statement is a server-side object that can be used to optimize
performance. When the <command>PREPARE</command> statement is
executed, the specified statement is parsed, rewritten, and
planned. When an <command>EXECUTE</command> command is subsequently
issued, the prepared statement need only be executed. Thus, the
parsing, rewriting, and planning stages are only performed once,
instead of every time the statement is executed.
</para>
<para>
Prepared statements can take parameters: values that are
substituted into the statement when it is executed. To include
parameters in a prepared statement, supply a list of data types in
the <command>PREPARE</command> statement, and, in the statement to
be prepared itself, refer to the parameters by position using
<literal>$1</literal>, <literal>$2</literal>, etc. When executing
the statement, specify the actual values for these parameters in
the <command>EXECUTE</command> statement. Refer to <xref
linkend="sql-execute" endterm="sql-execute-title"> for more
information about that.
</para>
<para>
Prepared statements are only stored in and for the duration of
the current database session. When
the session ends, the prepared statement is forgotten, and so it must be
recreated before being used again. This also means that a single
prepared statement cannot be used by multiple simultaneous database
clients; however, each client can create their own prepared statement
to use.
</para>
<para>
Prepared statements have the largest performance advantage when a
single session is being used to execute a large number of similar
statements. The performance difference will be particularly
significant if the statements are complex to plan or rewrite, for
example, if the query involves a join of many tables or requires
the application of several rules. If the statement is relatively simple
to plan and rewrite but relatively expensive to execute, the
performance advantage of prepared statements will be less noticeable.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="PARAMETER">plan_name</replaceable></term>
<listitem>
<para>
An arbitrary name given to this particular prepared query. It
must be unique within a single session, and is used to execute
or remove a previously prepared query.
An arbitrary name given to this particular prepared
statement. It must be unique within a single session and is
subsequently used to execute or deallocate a previously prepared
statement.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">datatype</replaceable></term>
<listitem>
<para>
The data-type of a parameter to the prepared query.
To refer to the parameters in the prepared query itself,
use <literal>$1</literal>, <literal>$2</literal>, etc.
The data type of a parameter to the prepared statement. To
refer to the parameters in the prepared statement itself, use
<literal>$1</literal>, <literal>$2</literal>, etc.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">query</replaceable></term>
<term><replaceable class="PARAMETER">statement</replaceable></term>
<listitem>
<para>
Any <command>SELECT</>, <command>INSERT</>, <command>UPDATE</>,
or <command>DELETE</> query.
or <command>DELETE</> statement.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="R2-SQL-PREPARE-2">
<refsect2info>
<date>2002-08-12</date>
</refsect2info>
<title>
Outputs
</title>
<para>
</refsect1>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>
<returnvalue>PREPARE</returnvalue>
</computeroutput></term>
<term><computeroutput>PREPARE</computeroutput></term>
<listitem>
<para>
The query has been prepared successfully.
Message returned if the statement has been prepared successfully.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-PREPARE-1">
<refsect1info>
<date>2002-08-12</date>
</refsect1info>
<title>
Description
</title>
<para>
<command>PREPARE</command> creates a prepared query. A prepared
query is a server-side object that can be used to optimize
performance. When the <command>PREPARE</command> statement is
executed, the specified query is parsed, rewritten, and
planned. When a subsequent <command>EXECUTE</command> statement is
issued, the prepared query need only be executed. Thus, the
parsing, rewriting, and planning stages are only performed once,
instead of every time the query is executed.
</para>
<para>
Prepared queries can take parameters: values that are
substituted into the query when it is executed. To specify the
parameters to a prepared query, include a list of data-types with
the <command>PREPARE</command> statement. In the query itself, you
can refer to the parameters by position using
<literal>$1</literal>, <literal>$2</literal>, etc. When executing
the query, specify the actual values for these parameters in the
<command>EXECUTE</command> statement -- refer to <xref
linkend="sql-execute" endterm="sql-execute-title">
for more information.
</para>
<para>
Prepared queries are stored locally (in the current backend), and
only exist for the duration of the current database session. When
the client exits, the prepared query is forgotten, and so it must be
re-created before being used again. This also means that a single
prepared query cannot be used by multiple simultaneous database
clients; however, each client can create their own prepared query
to use.
</para>
<para>
Prepared queries have the largest performance advantage when a
single backend is being used to execute a large number of similar
queries. The performance difference will be particularly
significant if the queries are complex to plan or rewrite. For
example, if the query involves a join of many tables or requires
the application of several rules. If the query is relatively simple
to plan and rewrite but relatively expensive to execute, the
performance advantage of prepared queries will be less noticeable.
</para>
</refsect1>
<refsect2 id="R2-SQL-PREPARE-3">
<refsect2info>
<date>2002-08-12</date>
</refsect2info>
<title>
Notes
</title>
<refsect1>
<title>Notes</title>
<para>
In some situations, the query plan produced by
<productname>PostgreSQL</productname> for a prepared query may be
inferior to the plan produced if the query were submitted and
executed normally. This is because when the query is planned (and
the optimizer attempts to determine the optimal query plan), the
actual values of any parameters specified in the query are
In some situations, the query plan produced by for a prepared
statement may be inferior to the plan produced if the statement
were submitted and executed normally. This is because when the
statement is planned and the planer attempts to determine the
optimal query plan, the actual values of any parameters specified
in the statement are
unavailable. <productname>PostgreSQL</productname> collects
statistics on the distribution of data in the table, and can use
constant values in a query to make guesses about the likely
result of executing the query. Since this data is unavailable when
planning prepared queries with parameters, the chosen plan may be
sub-optimal. To examine the query plan
constant values in a statement to make guesses about the likely
result of executing the statement. Since this data is unavailable
when planning prepared statements with parameters, the chosen plan
may be suboptimal. To examine the query plan
<productname>PostgreSQL</productname> has chosen for a prepared
query, use <command>EXPLAIN EXECUTE</command>.
statement, use <command>EXPLAIN EXECUTE</command>.
</para>
<para>
For more information on query planning and the statistics
collected by <productname>PostgreSQL</productname> for query
optimization purposes, see the <xref linkend="sql-analyze"
endterm="sql-analyze-title"> documentation.
For more information on query planning and the statistics collected
by <productname>PostgreSQL</productname> for that purpose, see
the <xref linkend="sql-analyze" endterm="sql-analyze-title">
documentation.
</para>
</refsect2>
</refsect1>
<refsect1 id="R1-SQL-PREPARE-3">
<title>
Compatibility
</title>
<refsect2 id="R2-SQL-PREPARE-4">
<refsect2info>
<date>2002-08-12</date>
</refsect2info>
<title>
SQL92
</title>
<refsect1>
<title>Compatibility</title>
<para>
SQL92 includes a <command>PREPARE</command> statement, but it is
only for use in embedded SQL clients. The
<command>PREPARE</command> statement implemented by
<productname>PostgreSQL</productname> also uses a somewhat
different syntax.
The SQL standard includes a <command>PREPARE</command> statement,
but it is only for use in embedded SQL. This version of the
<command>PREPARE</command> statement also uses a somewhat different
syntax.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/reindex.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/reindex.sgml,v 1.16 2003/03/25 16:15:43 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/reindex.sgml,v 1.17 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,124 +8,31 @@ PostgreSQL documentation
<refentrytitle id="SQL-REINDEX-TITLE">REINDEX</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
REINDEX
</refname>
<refpurpose>
rebuild corrupted indexes
</refpurpose>
<refname>REINDEX</refname>
<refpurpose>rebuild indexes</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>2000-03-30</date>
</refsynopsisdivinfo>
<synopsis>
<synopsis>
REINDEX { DATABASE | TABLE | INDEX } <replaceable class="PARAMETER">name</replaceable> [ FORCE ]
</synopsis>
<refsect2 id="R2-SQL-REINDEX-1">
<refsect2info>
<date>2000-03-30</date>
</refsect2info>
<title>
Inputs
</title>
<para>
<variablelist>
<varlistentry>
<term>DATABASE</term>
<listitem>
<para>
Recreate all system indexes of a specified database. Indexes on
user tables are not included. This form of <command>REINDEX</> can
only be used in standalone mode (see below).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>TABLE</term>
<listitem>
<para>
Recreate all indexes of a specified table.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>INDEX</term>
<listitem>
<para>
Recreate a specified index.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">name</replaceable></term>
<listitem>
<para>
The name of the specific database/table/index to be reindexed.
Table and index names may be schema-qualified.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>FORCE</term>
<listitem>
<para>
Force rebuild of system indexes. Without this keyword
<command>REINDEX</> skips system indexes that are not marked invalid.
FORCE is irrelevant for <command>REINDEX INDEX</>, or when reindexing
user indexes.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="R2-SQL-REINDEX-2">
<refsect2info>
<date>2000-03-30</date>
</refsect2info>
<title>
Outputs
</title>
<para>
<variablelist>
<varlistentry>
<term><computeroutput>
REINDEX
</computeroutput></term>
<listitem>
<para>
Message returned if the table is successfully reindexed.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</synopsis>
</refsynopsisdiv>
<refsect1 id="R1-SQL-REINDEX-1">
<refsect1info>
<date>2000-03-30</date>
</refsect1info>
<title>
Description
</title>
<refsect1>
<title>Description</title>
<para>
<command>REINDEX</command> rebuilds an index based on the data
stored in the table, replacing the old copy of the index. There are
two main reasons to use <command>REINDEX</command>:
<orderedlist>
<itemizedlist>
<listitem>
<para>
An index has become corrupted, and no longer contains valid
data. Although in theory this should never be necessary, in
data. Although in theory this should never happen, in
practice indexes may become corrupted due to software bugs or
hardware failures. <command>REINDEX</command> provides a
recovery method.
......@@ -135,146 +42,161 @@ REINDEX
<listitem>
<para>
The index in question contains a lot of dead index pages that
are not being reclaimed. This can occur with B+-tree indexes
are not being reclaimed. This can occur with B-tree indexes in PostgreSQL
under certain access patterns. <command>REINDEX</command>
provides a way to reduce the space consumption of the index by
writing a new version of the index without the dead pages. See
<xref linkend="routine-reindex"> for more information. The rest of this reference page
mostly discusses how to use <command>REINDEX</command> to
recover from index corruption.
<xref linkend="routine-reindex"> for more information.
</para>
</listitem>
</orderedlist>
</itemizedlist>
</para>
<para>
If you suspect corruption of an index on a user table, you can
simply rebuild that index, or all indexes on the table, using
<command>REINDEX INDEX</command> or <command>REINDEX TABLE</command>.
<command>REINDEX INDEX</command> or <command>REINDEX
TABLE</command>. Another approach to dealing with a corrupted
user-table index is just to drop and recreate it. This may in fact
be preferable if you would like to maintain some semblance of
normal operation on the table meanwhile. <command>REINDEX</>
acquires exclusive lock on the table, while <command>CREATE
INDEX</> only locks out writes not reads of the table.
</para>
<para>
Things are more difficult if you need to recover from corruption of
an index on a system table. In this case it's important for the
system to not have used any of the suspect indexes itself.
(Indeed, in this sort of scenario you may find that server
processes are crashing immediately at start-up, due to reliance on
the corrupted indexes.) To recover safely, the server must be shut
down and a stand-alone <productname>PostgreSQL</productname> server
must be started instead with the command-line options
<option>-O</option> and <option>-P</option>. (These options allow
system table modifications and prevent use of system indexes,
respectively.) Then, <command>REINDEX DATABASE</>,
<command>REINDEX TABLE</>, or <command>REINDEX INDEX</> can be
issued, depending on how much you want to reconstruct. If in
doubt, use <command>REINDEX DATABASE FORCE</> to force
reconstruction of all system indexes in the database. Then quit
the standalone server session and restart the real server.
</para>
<para>
See the <xref linkend="app-postgres"> reference page for more
information about how to interact with the stand-alone server
interface.
</para>
</refsect1>
<note>
<para>
Another approach to dealing with a corrupted user-table index is
just to drop and recreate it. This may in fact be preferable if
you would like to maintain some semblance of normal operation on
the table meanwhile. <command>REINDEX</> acquires exclusive lock
on the table, while <command>CREATE INDEX</> only locks out writes
not reads of the table.
</para>
</note>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><literal>DATABASE</literal></term>
<listitem>
<para>
Things are more difficult if you need to recover from corruption of an
index on a system table. In this case it's important for the backend
doing the recovery to not have used any of the suspect indexes itself.
(Indeed, in this sort of scenario you may find that backends are
crashing immediately at start-up, due to reliance on the corrupted
indexes.) To recover safely, the postmaster must be shut down and a
stand-alone <productname>PostgreSQL</productname> backend must be
started instead, giving it
the command-line options -O and -P (these options allow system table
modifications and prevent use of system indexes, respectively). Then
issue <command>REINDEX DATABASE</>, <command>REINDEX TABLE</>,
<command>REINDEX INDEX</>, or depending on how much you want to reconstruct.
If in doubt, use <command>REINDEX DATABASE FORCE</> to force reconstruction
of all system indexes in the database. Then quit the standalone backend
and restart the postmaster.
Recreate all system indexes of a specified database. Indexes on
user tables are not included. This form of <command>REINDEX</>
can only be used in stand-alone mode (see above).
</para>
</listitem>
</varlistentry>
<para>
Since this is likely the only situation when most people will ever use
a standalone backend, some usage notes might be in order:
<itemizedlist>
<varlistentry>
<term><literal>TABLE</literal></term>
<listitem>
<para>
Start the backend with a command like
<screen>
<userinput>postgres -D $PGDATA -O -P my_database</userinput>
</screen>
Provide the correct path to the database area with <option>-D</>, or
make sure that the environment variable <envar>PGDATA</> is set.
Also specify the name of the particular database you want to work in.
Recreate all indexes of a specified table.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>INDEX</literal></term>
<listitem>
<para>
You can issue any SQL command, not only <command>REINDEX</>.
Recreate a specified index.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">name</replaceable></term>
<listitem>
<para>
Be aware that the standalone backend treats newline as the command
entry terminator; there is no intelligence about semicolons,
as there is in <application>psql</>. To continue a command
across multiple lines, you must type backslash just before each
newline except the last one.
Also, you won't have any of the conveniences of command-line editing
(no command history, for example).
The name of the specific database, table, or index to be
reindexed. Table and index names may be schema-qualified.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>FORCE</literal></term>
<listitem>
<para>
To quit the backend, type <acronym>EOF</> (<keycombo
action="simul"><keycap>Control</><keycap>D</></>, usually).
Force rebuild of system indexes. Without this key word,
<command>REINDEX</> skips system indexes that are not marked
invalid. <literal>FORCE</> is irrelevant for <command>REINDEX
INDEX</> or when reindexing user indexes.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</itemizedlist>
<refsect1>
<title>Diagnostics</title>
See the <xref linkend="app-postgres"> reference page for more information.
<variablelist>
<varlistentry>
<term><computeroutput>REINDEX</computeroutput></term>
<listitem>
<para>
Message returned if the indexes were successfully recreated.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="R1-SQL-REINDEX-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
Recreate the indexes on the table <literal>mytable</literal>:
Recreate the indexes on the table <literal>my_table</literal>:
<programlisting>
REINDEX TABLE mytable;
</programlisting>
<programlisting>
REINDEX TABLE my_table;
</programlisting>
</para>
<para>
Rebuild a single index:
<programlisting>
REINDEX INDEX my_index;
</programlisting>
<programlisting>
REINDEX INDEX my_index;
</programlisting>
</para>
<para>
Rebuild all system indexes (this will only work in a standalone backend):
Rebuild all system indexes (this will only work in a stand-alone
server session):
<programlisting>
REINDEX DATABASE my_database FORCE;
</programlisting>
<programlisting>
REINDEX DATABASE my_database FORCE;
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-REINDEX-3">
<title>
Compatibility
</title>
<refsect1>
<title>Compatibility</title>
<refsect2 id="R2-SQL-REINDEX-4">
<refsect2info>
<date>2000-03-30</date>
</refsect2info>
<title>
SQL92
</title>
<para>
There is no <command>REINDEX</command> in <acronym>SQL92</acronym>.
There is no <command>REINDEX</command> command in the SQL standard.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/revoke.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/revoke.sgml,v 1.25 2003/01/23 23:38:53 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/revoke.sgml,v 1.26 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -53,19 +53,19 @@ REVOKE [ GRANT OPTION FOR ]
<title>Description</title>
<para>
<command>REVOKE</command> allows the creator of an object to revoke
previously granted permissions from one or more users or groups of users.
The key word <literal>PUBLIC</literal> refers to the implicitly defined
group of all users.
The <command>REVOKE</command> command revokes previously granted
privileges from one or more users or groups of users. The key word
<literal>PUBLIC</literal> refers to the implicitly defined group of
all users.
</para>
<para>
Note that any particular user will have the sum
of privileges granted directly to him, privileges granted to any group he
is presently a member of, and privileges granted to
<literal>PUBLIC</literal>. Thus, for example, revoking SELECT privilege
<literal>PUBLIC</literal>. Thus, for example, revoking <literal>SELECT</> privilege
from <literal>PUBLIC</literal> does not necessarily mean that all users
have lost SELECT privilege on the object: those who have it granted
have lost <literal>SELECT</> privilege on the object: those who have it granted
directly or via a group will still have it.
</para>
......@@ -138,15 +138,12 @@ REVOKE ALL PRIVILEGES ON kinds FROM manuel;
<refsect1 id="SQL-REVOKE-compatibility">
<title>Compatibility</title>
<refsect2>
<title>SQL92</title>
<para>
The compatibility notes of the <xref linkend="sql-grant" endterm="sql-grant-title"> command
apply analogously to <command>REVOKE</command>. The syntax summary is:
<synopsis>
REVOKE [ GRANT OPTION FOR ] { SELECT | INSERT | UPDATE | DELETE | REFERENCES }
REVOKE [ GRANT OPTION FOR ] <replaceable class="PARAMETER">privileges</replaceable>
ON <replaceable class="parameter">object</replaceable> [ ( <replaceable class="parameter">column</replaceable> [, ...] ) ]
FROM { PUBLIC | <replaceable class="parameter">username</replaceable> [, ...] }
{ RESTRICT | CASCADE }
......@@ -154,7 +151,6 @@ REVOKE [ GRANT OPTION FOR ] { SELECT | INSERT | UPDATE | DELETE | REFERENCES }
One of <literal>RESTRICT</literal> or <literal>CASCADE</literal>
is required.
</para>
</refsect2>
</refsect1>
<refsect1>
......
doc/src/sgml/ref/rollback.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/rollback.sgml,v 1.13 2002/05/18 15:44:47 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/rollback.sgml,v 1.14 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,48 +8,49 @@ PostgreSQL documentation
<refentrytitle id="SQL-ROLLBACK-TITLE">ROLLBACK</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
ROLLBACK
</refname>
<refpurpose>
abort the current transaction
</refpurpose>
<refname>ROLLBACK</refname>
<refpurpose>abort the current transaction</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1999-07-20</date>
</refsynopsisdivinfo>
<synopsis>
<synopsis>
ROLLBACK [ WORK | TRANSACTION ]
</synopsis>
<refsect2 id="R2-SQL-ROLLBACK-1">
<refsect2info>
<date>1998-09-24</date>
</refsect2info>
<title>
Inputs
</title>
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
None.
<command>ROLLBACK</command> rolls back the current transaction and causes
all the updates made by the transaction to be discarded.
</para>
</refsect2>
<refsect2 id="R2-SQL-ROLLBACK-2">
<refsect2info>
<date>1998-09-24</date>
</refsect2info>
<title>
Outputs
</title>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><literal>WORK</literal></term>
<term><literal>TRANSACTION</literal></term>
<listitem>
<para>
Optional key words. They have no effect.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>
ROLLBACK
</computeroutput></term>
<term><computeroutput>ROLLBACK</computeroutput></term>
<listitem>
<para>
Message returned if successful.
......@@ -58,9 +59,7 @@ ROLLBACK
</varlistentry>
<varlistentry>
<term><computeroutput>
WARNING: ROLLBACK: no transaction in progress
</computeroutput></term>
<term><computeroutput>WARNING: ROLLBACK: no transaction in progress</computeroutput></term>
<listitem>
<para>
If there is not any transaction currently in progress.
......@@ -68,69 +67,36 @@ WARNING: ROLLBACK: no transaction in progress
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
</refsect1>
<refsect1 id="R1-SQL-ROLLBACK-1">
<refsect1info>
<date>1998-09-24</date>
</refsect1info>
<title>
Description
</title>
<refsect1>
<title>Notes</title>
<para>
<command>ROLLBACK</command> rolls back the current transaction and causes
all the updates made by the transaction to be discarded.
</para>
<refsect2 id="R2-SQL-ROLLBACK-3">
<refsect2info>
<date>1998-09-24</date>
</refsect2info>
<title>
Notes
</title>
<para>
Use <xref linkend="SQL-COMMIT" endterm="SQL-COMMIT-TITLE">
to successfully terminate a transaction.
<xref linkend="SQL-ABORT" endterm="SQL-ABORT-TITLE"> is a
synonym for <command>ROLLBACK</command>.
Use <xref linkend="SQL-COMMIT" endterm="SQL-COMMIT-TITLE"> to
successfully terminate a transaction.
</para>
</refsect2>
</refsect1>
<refsect1 id="R1-SQL-ROLLBACK-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
To abort all changes:
<programlisting>
ROLLBACK WORK;
</programlisting>
<programlisting>
ROLLBACK;
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-ROLLBACK-3">
<title>
Compatibility
</title>
<refsect2 id="R2-SQL-ROLLBACK-4">
<refsect2info>
<date>1998-09-24</date>
</refsect2info>
<title>
SQL92
</title>
<refsect1>
<title>Compatibility</title>
<para>
<acronym>SQL92</acronym> only specifies the two forms <literal>ROLLBACK</literal>
and <literal>ROLLBACK WORK</literal>. Otherwise full compatibility.
The SQL standard only specifies the two forms
<literal>ROLLBACK</literal> and <literal>ROLLBACK
WORK</literal>. Otherwise, this command is fully conforming.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/start_transaction.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.4 2003/01/10 22:03:27 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.5 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
<refentry id="SQL-START-TRANSACTION">
<docinfo>
<date>2002-07-26</date>
</docinfo>
<refmeta>
<refentrytitle id="SQL-START-TRANSACTION-TITLE">START TRANSACTION</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
......@@ -19,80 +15,66 @@ PostgreSQL documentation
</refnamediv>
<refsynopsisdiv>
<synopsis>
<synopsis>
START TRANSACTION [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
</synopsis>
</synopsis>
</refsynopsisdiv>
<refsect2 id="R2-SQL-START-TRANSACTION-1">
<refsect2info>
<date>1998-09-27</date>
</refsect2info>
<title>
Inputs
</title>
<refsect1>
<title>Description</title>
<para>
None.
This command begins a new transaction. If the isolation level or
read/write mode is specified, the new transaction has those
characteristics, as if <xref linkend="sql-set-transaction"
endterm="sql-set-transaction-title"> was executed. In all other
respects, the behavior of this command is identical to the <xref
linkend="sql-begin" endterm="sql-begin-title"> command.
</para>
</refsect2>
</refsect1>
<refsect2 id="R2-SQL-START-TRANSACTION-2">
<refsect2info>
<date>1998-09-27</date>
</refsect2info>
<title>
Outputs
</title>
<refsect1>
<title>Parameters</title>
<para>
See under <xref linkend="sql-set-transaction"
endterm="sql-set-transaction-title"> about the meaning of the
parameters.
</para>
</refsect1>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>
START TRANSACTION
</computeroutput></term>
<term><computeroutput>START TRANSACTION</computeroutput></term>
<listitem>
<para>
Message returned if successful.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><computeroutput>
WARNING: BEGIN: already a transaction in progress
</computeroutput></term>
<term><computeroutput>WARNING: BEGIN: already a transaction in progress</computeroutput></term>
<listitem>
<para>
If there is already a transaction in progress when the
command is issued.
Message returned if there was already a transaction in progress
when the command was issued.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
This command begins a new transaction. If the isolation level or
read/write mode is specified, the new transaction has those
characteristics, as if <xref linkend="sql-set-transaction"
endterm="sql-set-transaction-title"> was executed. In all other
respects, the behavior of this command is identical to the <xref
linkend="sql-begin" endterm="sql-begin-title"> command.
</para>
</refsect1>
<refsect1 id="R1-SQL-START-TRANSACTION-3">
<refsect1>
<title>Compatibility</title>
<para>
SQL99; but see also the compatibility section of <xref
linkend="sql-set-transaction" endterm="sql-set-transaction-title">.
This command conforms to the SQL standard; but see also the
compatibility section of <xref linkend="sql-set-transaction"
endterm="sql-set-transaction-title">.
</para>
</refsect1>
</refentry>
......
doc/src/sgml/ref/truncate.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/truncate.sgml,v 1.9 2002/12/06 03:15:07 momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/truncate.sgml,v 1.10 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,30 +8,31 @@ PostgreSQL documentation
<refentrytitle id="SQL-TRUNCATE-TITLE">TRUNCATE</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
TRUNCATE
</refname>
<refpurpose>
empty a table
</refpurpose>
<refname>TRUNCATE</refname>
<refpurpose>empty a table</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1999-07-20</date>
</refsynopsisdivinfo>
<synopsis>
<synopsis>
TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable>
</synopsis>
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<refsect2 id="R2-SQL-TRUNCATE-1">
<refsect2info>
<date>1998-09-08</date>
</refsect2info>
<title>
Inputs
</title>
<para>
<command>TRUNCATE</command> quickly removes all rows from a
table. It has the same effect as an unqualified
<command>DELETE</command> but since it does not actually scan the
table it is faster. This is most useful on large tables.
</para>
</refsect1>
<refsect1>
<title>Parameter</title>
<variablelist>
<varlistentry>
......@@ -43,78 +44,41 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsect1>
<refsect2 id="R2-SQL-TRUNCATE-2">
<refsect2info>
<date>1998-09-08</date>
</refsect2info>
<title>
Outputs
</title>
<para>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>
TRUNCATE TABLE
</computeroutput></term>
<term><computeroutput>TRUNCATE TABLE</computeroutput></term>
<listitem>
<para>
Message returned if the table is successfully truncated.
Message returned if the table was successfully truncated.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-TRUNCATE-1">
<refsect1info>
<date>1998-09-08</date>
</refsect1info>
<title>
Description
</title>
<para>
<command>TRUNCATE</command> quickly removes all rows from a
table. It has the same effect as an unqualified
<command>DELETE</command> but since it does not actually scan the
table it is faster. This is most useful on large tables.
</para>
</refsect1>
<refsect1 id="R1-SQL-TRUNCATE-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
Truncate the table <literal>bigtable</literal>:
<programlisting>
<programlisting>
TRUNCATE TABLE bigtable;
</programlisting>
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-TRUNCATE-3">
<title>
Compatibility
</title>
<refsect1>
<title>Compatibility</title>
<refsect2 id="R2-SQL-TRUNCATE-4">
<refsect2info>
<date>1998-09-08</date>
</refsect2info>
<title>
SQL92
</title>
<para>
There is no <command>TRUNCATE</command> in <acronym>SQL92</acronym>.
There is no <command>TRUNCATE</command> command in the SQL standard.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/unlisten.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/unlisten.sgml,v 1.20 2002/09/21 18:32:54 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/unlisten.sgml,v 1.21 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,136 +8,101 @@ PostgreSQL documentation
<refentrytitle>UNLISTEN</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
UNLISTEN
</refname>
<refpurpose>
stop listening for a notification
</refpurpose>
<refname>UNLISTEN</refname>
<refpurpose>stop listening for a notification</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1998-10-19</date>
</refsynopsisdivinfo>
<synopsis>
UNLISTEN { <replaceable class="PARAMETER">notifyname</replaceable> | * }
</synopsis>
<refsect2 id="R2-SQL-UNLISTEN-1">
<refsect2info>
<date>1998-10-19</date>
</refsect2info>
<title>
Inputs
</title>
<synopsis>
UNLISTEN { <replaceable class="PARAMETER">name</replaceable> | * }
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>UNLISTEN</command> is used to remove an existing
registration for <command>NOTIFY</command> events.
<command>UNLISTEN</command> cancels any existing registration of
the current <productname>PostgreSQL</productname> session as a
listener on the notification <replaceable
class="PARAMETER">name</replaceable>. The special wildcard
<literal>*</literal> cancels all listener registrations for the
current session.
</para>
<para>
<xref endterm="sql-notify-title" linkend="sql-notify">
contains a more extensive
discussion of the use of <command>LISTEN</command> and
<command>NOTIFY</command>.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="PARAMETER">notifyname</replaceable></term>
<term><replaceable class="PARAMETER">name</replaceable></term>
<listitem>
<para>
Name of previously registered notify condition.
Name of a notification (any identifier).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>*</literal></term>
<listitem>
<para>
All current listen registrations for this backend are cleared.
All current listen registrations for this session are cleared.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="R2-SQL-UNLISTEN-2">
<refsect2info>
<date>1998-10-19</date>
</refsect2info>
<title>
Outputs
</title>
<para>
</refsect1>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>
<returnvalue>UNLISTEN</returnvalue>
</computeroutput></term>
<term><computeroutput>UNLISTEN</computeroutput></term>
<listitem>
<para>
Acknowledgment that statement has executed.
Message returned when the command has executed.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-UNLISTEN-1">
<refsect1info>
<date>1998-10-19</date>
</refsect1info>
<title>
Description
</title>
</refsect1>
<para>
<command>UNLISTEN</command>
is used to remove an existing <command>NOTIFY</command> registration.
<command>UNLISTEN</command> cancels any existing registration of the current
<productname>PostgreSQL</productname> session as a listener on the notify
condition <replaceable class="PARAMETER">notifyname</replaceable>.
The special condition wildcard <literal>*</literal> cancels all listener registrations
for the current session.
</para>
<refsect1>
<title>Notes</title>
<para>
<xref endterm="sql-notify-title" linkend="sql-notify">
contains a more extensive
discussion of the use of <command>LISTEN</command> and
<command>NOTIFY</command>.
You unlisten something you were not listening for; no warning or error will appear.
</para>
<refsect2 id="R2-SQL-UNLISTEN-3">
<refsect2info>
<date>1998-10-19</date>
</refsect2info>
<title>
Notes
</title>
<para>
<replaceable class="PARAMETER">notifyname</replaceable>
need not be a valid class name but can be any string valid
as a name up to 64 characters long.
</para>
<para>
The backend does not complain if you unlisten something you were not
listening for.
Each backend will automatically execute <command>UNLISTEN *</command> when
exiting.
At the end of each session, <command>UNLISTEN *</command> ist
automatically executed.
</para>
</refsect2>
</refsect1>
<refsect1 id="R1-SQL-UNLISTEN-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
To subscribe to an existing registration:
To make a registration:
<programlisting>
LISTEN virtual;
LISTEN
NOTIFY virtual;
NOTIFY
Asynchronous NOTIFY 'virtual' from backend with pid '8448' received
</programlisting>
</para>
......@@ -148,30 +113,18 @@ Asynchronous NOTIFY 'virtual' from backend with pid '8448' received
<programlisting>
UNLISTEN virtual;
UNLISTEN
NOTIFY virtual;
NOTIFY
-- notice no NOTIFY event is received
-- no NOTIFY event is received
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-UNLISTEN-3">
<title>
Compatibility
</title>
<refsect2 id="R2-SQL-UNLISTEN-4">
<refsect2info>
<date>1998-10-19</date>
</refsect2info>
<title>
SQL92
</title>
<refsect1>
<title>Compatibility</title>
<para>
There is no <command>UNLISTEN</command> in <acronym>SQL92</acronym>.
There is no <command>UNLISTEN</command> command in the SQL standard.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/update.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/update.sgml,v 1.20 2002/08/15 02:59:18 momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/update.sgml,v 1.21 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,50 +8,57 @@ PostgreSQL documentation
<refentrytitle id="SQL-UPDATE-TITLE">UPDATE</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
UPDATE
</refname>
<refpurpose>
update rows of a table
</refpurpose>
<refname>UPDATE</refname>
<refpurpose>update rows of a table</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1999-07-20</date>
</refsynopsisdivinfo>
<synopsis>
UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> SET <replaceable class="PARAMETER">col</replaceable> = <replaceable class="PARAMETER">expression</replaceable> [, ...]
<synopsis>
UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> SET <replaceable class="PARAMETER">column</replaceable> = <replaceable class="PARAMETER">expression</replaceable> [, ...]
[ FROM <replaceable class="PARAMETER">fromlist</replaceable> ]
[ WHERE <replaceable class="PARAMETER">condition</replaceable> ]
</synopsis>
<refsect2 id="R2-SQL-UPDATE-1">
<refsect2info>
<date>1998-09-24</date>
</refsect2info>
<title>
Inputs
</title>
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>UPDATE</command> changes the values of the specified
columns in all rows that satisfy the condition. Only the columns to
be modified need appear as columns in the statement.
</para>
<para>
By default, <command>UPDATE</command> will update rows in the
specified table and all its subtables. If you wish to only update
the specific table mentioned, you must use the <literal>ONLY</>
clause.
</para>
<para>
You must have the <literal>UPDATE</literal> privilege on the table
to update it, as well as the <literal>SELECT</literal>
privilege to any table whose values are read in the <replaceable
class="parameter">condition</replaceable>.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="PARAMETER">table</replaceable></term>
<listitem>
<para>
The name (optionally schema-qualified) of an existing table. If
<literal>ONLY</> is specified, only that table is updated. If
<literal>ONLY</> is not specified, the table and all its
descendant tables (if any) are updated. <literal>*</> can be
appended to the table name to indicate that descendant tables are
to be scanned, but in the current version, this is the default
behavior. (In releases before 7.1, <literal>ONLY</> was the
default behavior.) The default can be altered by changing the
<option>SQL_INHERITANCE</option> configuration option.
The name (optionally schema-qualified) of the table to update.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">column</replaceable></term>
<listitem>
......@@ -60,152 +67,77 @@ UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> SET <replacea
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">expression</replaceable></term>
<listitem>
<para>
A valid expression or value to assign to column.
An expression or value to assign to the column.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">fromlist</replaceable></term>
<listitem>
<para>
A <productname>PostgreSQL</productname>
non-standard extension to allow columns
from other tables to appear in the WHERE condition.
A list of table expressions, allowing columns from other tables
to appear in the <literal>WHERE</> condition.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">condition</replaceable></term>
<listitem>
<para>
Refer to the SELECT statement for a further description
of the WHERE clause.
A value expression that returns a value of type
<type>boolean</type> that determines the rows which are to be
updated.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsect1>
<refsect2 id="R2-SQL-UPDATE-2">
<refsect2info>
<date>1998-09-24</date>
</refsect2info>
<title>
Outputs
</title>
<refsect1>
<title>Diagnostics</title>
<para>
<variablelist>
<varlistentry>
<term><computeroutput>
UPDATE <replaceable class="parameter">#</replaceable>
</computeroutput></term>
<term><computeroutput>UPDATE <replaceable class="parameter">count</replaceable></computeroutput></term>
<listitem>
<para>
Message returned if successful.
The <replaceable class="parameter">#</replaceable>
means the number of rows updated.
If <replaceable class="parameter">#</replaceable>
is 0 no rows are updated.
Message returned if successful. The value <replaceable
class="parameter">count</replaceable> is the number of rows
updated. If <replaceable class="parameter">count</replaceable>
is 0, no rows were updated.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-UPDATE-1">
<refsect1info>
<date>1998-09-24</date>
</refsect1info>
<title>
Description
</title>
<para>
<command>UPDATE</command> changes the values of the columns specified for
all rows which satisfy condition. Only the columns
to be modified need appear as columns in the statement.
</para>
<para>
Array references use the same syntax found in
<xref linkend="sql-select" endterm="sql-select-title">.
That is, either single array elements, a range of array
elements or the entire array may be replaced with a single
query.
</para>
<para>
You must have write access to the table in order to modify
it, as well as read access to any table whose values are
mentioned in the WHERE condition.
</para>
<para>
By default UPDATE will update tuples in the table specified
and all its sub-tables. If you wish to only update the
specific table mentioned, you should use the ONLY clause.
</para>
</refsect1>
<refsect1 id="R1-SQL-UPDATE-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
Change word <literal>Drama</> with <literal>Dramatic</> on column <structfield>kind</>:
Change the word <literal>Drama</> to <literal>Dramatic</> in the
column <structfield>kind</> of the table <literal>films</literal>:
<programlisting>
UPDATE films
SET kind = 'Dramatic'
WHERE kind = 'Drama';
SELECT *
FROM films
WHERE kind = 'Dramatic' OR kind = 'Drama';
code | title | did | date_prod | kind | len
-------+---------------+-----+------------+----------+-------
BL101 | The Third Man | 101 | 1949-12-23 | Dramatic | 01:44
P_302 | Becket | 103 | 1964-02-03 | Dramatic | 02:28
M_401 | War and Peace | 104 | 1967-02-12 | Dramatic | 05:57
T_601 | Yojimbo | 106 | 1961-06-16 | Dramatic | 01:50
DA101 | Das Boot | 110 | 1981-11-11 | Dramatic | 02:29
UPDATE filme SET kind = 'Dramatic' WHERE kind = 'Drama';
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-UPDATE-3">
<title>
Compatibility
</title>
<refsect2 id="R2-SQL-UPDATE-4">
<refsect2info>
<date>1998-09-24</date>
</refsect2info>
<title>
SQL92
</title>
<para>
<acronym>SQL92</acronym> defines a different syntax for
the positioned UPDATE statement:
<synopsis>
UPDATE <replaceable>table</replaceable> SET <replaceable>column</replaceable> = <replaceable>expression</replaceable> [, ...]
WHERE CURRENT OF <replaceable class="parameter">cursor</replaceable>
</synopsis>
<refsect1>
<title>Compatibility</title>
where <replaceable class="parameter">cursor</replaceable>
identifies an open cursor.
<para>
This command conforms to the SQL standard. The
<literal>FROM</literal> clause is a PostgreSQL extension.
</para>
</refsect2>
</refsect1>
</refentry>
......
doc/src/sgml/ref/vacuum.sgml
View file @ 20aae304
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/vacuum.sgml,v 1.30 2003/03/25 16:15:44 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/vacuum.sgml,v 1.31 2003/04/26 23:56:51 petere Exp $
PostgreSQL documentation
-->
......@@ -8,67 +8,115 @@ PostgreSQL documentation
<refentrytitle id="sql-vacuum-title">VACUUM</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
VACUUM
</refname>
<refpurpose>
garbage-collect and optionally analyze a database
</refpurpose>
<refname>VACUUM</refname>
<refpurpose>garbage-collect and optionally analyze a database</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>2001-08-26</date>
</refsynopsisdivinfo>
<synopsis>
<synopsis>
VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ <replaceable class="PARAMETER">table</replaceable> ]
VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] ANALYZE [ <replaceable class="PARAMETER">table</replaceable> [ (<replaceable class="PARAMETER">column</replaceable> [, ...] ) ] ]
</synopsis>
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<refsect2 id="R2-SQL-VACUUM-1">
<refsect2info>
<date>2001-07-10</date>
</refsect2info>
<title>
Inputs
</title>
<para>
<command>VACUUM</command> reclaims storage occupied by deleted tuples.
In normal <productname>PostgreSQL</productname> operation, tuples that
are deleted or obsoleted by an update are not physically removed from
their table; they remain present until a <command>VACUUM</command> is
done. Therefore it's necessary to do <command>VACUUM</command>
periodically, especially on frequently-updated tables.
</para>
<para>
With no parameter, <command>VACUUM</command> processes every table in the
current database. With a parameter, <command>VACUUM</command> processes
only that table.
</para>
<para>
<command>VACUUM ANALYZE</command> performs a <command>VACUUM</command>
and then an <command>ANALYZE</command> for each selected table. This
is a handy combination form for routine maintenance scripts. See
<xref linkend="sql-analyze" endterm="sql-analyze-title">
for more details about its processing.
</para>
<para>
Plain <command>VACUUM</command> (without <literal>FULL</>) simply reclaims
space and makes it
available for re-use. This form of the command can operate in parallel
with normal reading and writing of the table, as an exclusive lock
is not obtained. <command>VACUUM
FULL</command> does more extensive processing, including moving of tuples
across blocks to try to compact the table to the minimum number of disk
blocks. This form is much slower and requires an exclusive lock on each
table while it is being processed.
</para>
<para>
<command>FREEZE</command> is a special-purpose option that
causes tuples to be marked <quote>frozen</quote> as soon as possible,
rather than waiting until they are quite old. If this is done when there
are no other open transactions in the same database, then it is guaranteed
that all tuples in the database are <quote>frozen</> and will not be
subject to transaction ID wraparound problems, no matter how long the
database is left unvacuumed.
<command>FREEZE</command> is not recommended for routine use. Its only
intended usage is in connection with preparation of user-defined template
databases, or other databases that are completely read-only and will not
receive routine maintenance <command>VACUUM</> operations.
See <xref linkend="maintenance"> for details.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term>FULL</term>
<term><literal>FULL</literal></term>
<listitem>
<para>
Selects <quote>full</quote> vacuum, which may reclaim more space,
but takes much longer and exclusively locks the table.
Selects <quote>full</quote> vacuum, which may reclaim more
space, but takes much longer and exclusively locks the table.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>FREEZE</term>
<term><literal>FREEZE</literal></term>
<listitem>
<para>
Selects aggressive <quote>freezing</quote> of tuples.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>VERBOSE</term>
<term><literal>VERBOSE</literal></term>
<listitem>
<para>
Prints a detailed vacuum activity report for each table.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>ANALYZE</term>
<term><literal>ANALYZE</literal></term>
<listitem>
<para>
Updates statistics used by the optimizer to
determine the most efficient way to execute a query.
Updates statistics used by the planner to determine the most
efficient way to execute a query.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">table</replaceable></term>
<listitem>
......@@ -78,6 +126,7 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] ANALYZE [ <replaceable class="PARAMETER">
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">column</replaceable></term>
<listitem>
......@@ -87,23 +136,14 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] ANALYZE [ <replaceable class="PARAMETER">
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="R2-SQL-VACUUM-2">
<refsect2info>
<date>1998-10-04</date>
</refsect2info>
<title>
Outputs
</title>
<para>
</refsect1>
<refsect1>
<title>Diagnostics</title>
<variablelist>
<varlistentry>
<term><computeroutput>
<returnvalue>VACUUM</returnvalue>
</computeroutput></term>
<term><computeroutput>VACUUM</computeroutput></term>
<listitem>
<para>
The command is complete.
......@@ -112,9 +152,7 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] ANALYZE [ <replaceable class="PARAMETER">
</varlistentry>
<varlistentry>
<term><computeroutput>
INFO: --Relation <replaceable class="PARAMETER">table</replaceable>--
</computeroutput></term>
<term><computeroutput>INFO: --Relation <replaceable class="PARAMETER">table</replaceable>--</computeroutput></term>
<listitem>
<para>
The report header for <replaceable class="PARAMETER">table</replaceable>.
......@@ -123,12 +161,10 @@ INFO: --Relation <replaceable class="PARAMETER">table</replaceable>--
</varlistentry>
<varlistentry>
<term><computeroutput>
INFO: Pages 98: Changed 25, Reapped 74, Empty 0, New 0;
<term><computeroutput>INFO: Pages 98: Changed 25, Reapped 74, Empty 0, New 0;
Tup 1000: Vac 3000, Crash 0, UnUsed 0, MinLen 188, MaxLen 188;
Re-using: Free/Avail. Space 586952/586952; EndEmpty/Avail. Pages 0/74.
Elapsed 0/0 sec.
</computeroutput></term>
Elapsed 0/0 sec.</computeroutput></term>
<listitem>
<para>
The analysis for <replaceable class="PARAMETER">table</replaceable> itself.
......@@ -137,10 +173,8 @@ INFO: Pages 98: Changed 25, Reapped 74, Empty 0, New 0;
</varlistentry>
<varlistentry>
<term><computeroutput>
INFO: Index <replaceable class="PARAMETER">index</replaceable>: Pages 28;
Tuples 1000: Deleted 3000. Elapsed 0/0 sec.
</computeroutput></term>
<term><computeroutput>INFO: Index <replaceable class="PARAMETER">index</replaceable>: Pages 28;
Tuples 1000: Deleted 3000. Elapsed 0/0 sec.</computeroutput></term>
<listitem>
<para>
The analysis for an index on the target table.
......@@ -148,85 +182,21 @@ INFO: Index <replaceable class="PARAMETER">index</replaceable>: Pages 28;
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-SQL-VACUUM-1">
<refsect1info>
<date>2001-07-10</date>
</refsect1info>
<title>
Description
</title>
<para>
<command>VACUUM</command> reclaims storage occupied by deleted tuples.
In normal <productname>PostgreSQL</productname> operation, tuples that
are deleted or obsoleted by UPDATE are not physically removed from
their table; they remain present until a <command>VACUUM</command> is
done. Therefore it's necessary to do <command>VACUUM</command>
periodically, especially on frequently-updated tables.
</para>
<para>
With no parameter, <command>VACUUM</command> processes every table in the
current database. With a parameter, <command>VACUUM</command> processes
only that table.
</para>
<para>
<command>VACUUM ANALYZE</command> performs a <command>VACUUM</command>
and then an <command>ANALYZE</command> for each selected table. This
is a handy combination form for routine maintenance scripts. See
<xref linkend="sql-analyze" endterm="sql-analyze-title">
for more details about its processing.
</para>
<para>
Plain <command>VACUUM</command> (without <literal>FULL</>) simply reclaims
space and makes it
available for re-use. This form of the command can operate in parallel
with normal reading and writing of the table, as an exclusive lock
is not obtained. <command>VACUUM
FULL</command> does more extensive processing, including moving of tuples
across blocks to try to compact the table to the minimum number of disk
blocks. This form is much slower and requires an exclusive lock on each
table while it is being processed.
</para>
<para>
<command>FREEZE</command> is a special-purpose option that
causes tuples to be marked <quote>frozen</quote> as soon as possible,
rather than waiting until they are quite old. If this is done when there
are no other open transactions in the same database, then it is guaranteed
that all tuples in the database are <quote>frozen</> and will not be
subject to transaction ID wraparound problems, no matter how long the
database is left un-vacuumed.
<command>FREEZE</command> is not recommended for routine use. Its only
intended usage is in connection with preparation of user-defined template
databases, or other databases that are completely read-only and will not
receive routine maintenance <command>VACUUM</> operations.
See <xref linkend="maintenance"> for details.
</para>
</refsect1>
<refsect2 id="R2-SQL-VACUUM-3">
<refsect2info>
<date>2001-07-10</date>
</refsect2info>
<title>
Notes
</title>
<refsect1>
<title>Notes</title>
<para>
We recommend that active production databases be
<command>VACUUM</command>-ed frequently (at least nightly), in order to
vacuumed frequently (at least nightly), in order to
remove expired rows. After adding or deleting a large number
of records, it may be a good idea to issue a <command>VACUUM
of rows, it may be a good idea to issue a <command>VACUUM
ANALYZE</command> command for the affected table. This will update the
system catalogs with
the results of all recent changes, and allow the
<productname>PostgreSQL</productname> query optimizer to make better
choices in planning user queries.
<productname>PostgreSQL</productname> query planner to make better
choices in planning queries.
</para>
<para>
......@@ -236,20 +206,17 @@ INFO: Index <replaceable class="PARAMETER">index</replaceable>: Pages 28;
to occupy less disk space. <command>VACUUM FULL</command> will usually
shrink the table more than a plain <command>VACUUM</command> would.
</para>
</refsect2>
</refsect1>
<refsect1 id="R1-SQL-VACUUM-2">
<title>
Usage
</title>
<refsect1>
<title>Examples</title>
<para>
The following is an example from running <command>VACUUM</command> on a table
in the regression database:
<programlisting>
regression=> VACUUM VERBOSE ANALYZE onek;
<programlisting>
=> VACUUM VERBOSE ANALYZE onek;
INFO: --Relation onek--
INFO: Index onek_unique1: Pages 14; Tuples 1000: Deleted 3000.
CPU 0.00s/0.11u sec elapsed 0.12 sec.
......@@ -265,26 +232,16 @@ INFO: Pages 94: Changed 0, Empty 0; Tup 1000: Vac 3000, Keep 0, UnUsed 0.
Total CPU 0.05s/0.45u sec elapsed 0.59 sec.
INFO: Analyzing onek
VACUUM
</programlisting>
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-VACUUM-3">
<title>
Compatibility
</title>
<refsect2 id="R2-SQL-VACUUM-4">
<refsect2info>
<date>1998-10-04</date>
</refsect2info>
<title>
SQL92
</title>
<refsect1>
<title>Compatibility</title>
<para>
There is no <command>VACUUM</command> statement in <acronym>SQL92</acronym>.
There is no <command>VACUUM</command> statement in the SQL standard.
</para>
</refsect2>
</refsect1>
<refsect1>
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment