<!--
-$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
-->
</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>
<para>
To abort all changes:
<programlisting>
-ABORT WORK;
+ABORT;
</programlisting>
</para>
</refsect1>
<!--
-$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
-->
<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>
-
- <refsect2 id="R2-SQL-DEALLOCATE-1">
- <refsect2info>
- <date>2002-08-12</date>
- </refsect2info>
- <title>
- Inputs
- </title>
-
- <para>
- <variablelist>
- <varlistentry>
- <term>PREPARE</term>
- <listitem>
- <para>
- This keyword is ignored.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><replaceable class="PARAMETER">plan_name</replaceable></term>
- <listitem>
- <para>
- The name of the prepared query to remove.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
- <refsect2 id="R2-SQL-DEALLOCATE-2">
- <refsect2info>
- <date>2002-08-12</date>
- </refsect2info>
- <title>
- Outputs
- </title>
- <para>
- <variablelist>
- <varlistentry>
- <term><computeroutput>
- <returnvalue>DEALLOCATE</returnvalue>
- </computeroutput></term>
- <listitem>
- <para>
- The prepared query was removed successfully.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+ <refsynopsisdiv>
+<synopsis>
+DEALLOCATE [ PREPARE ] <replaceable class="parameter">plan_name</replaceable>
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-DEALLOCATE-1">
- <refsect1info>
- <date>2002-08-12</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <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.
+ <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 queries, see <xref
+ For more information on prepared statements, see <xref
linkend="sql-prepare" endterm="sql-prepare-title">.
</para>
</refsect1>
- <refsect1 id="R1-SQL-DEALLOCATE-2">
- <title>
- Compatibility
- </title>
+ <refsect1>
+ <title>Parameters</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><literal>PREPARE</literal></term>
+ <listitem>
+ <para>
+ This key word is ignored.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="parameter">plan_name</replaceable></term>
+ <listitem>
+ <para>
+ The name of the prepared statement to deallocate.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><computeroutput>DEALLOCATE</computeroutput></term>
+ <listitem>
+ <para>
+ Message returned if the prepared statement was deallocated successfully.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
- <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.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ The SQL standard includes a <command>DEALLOCATE</command>
+ statement, but it is only for use in embedded SQL.
+ </para>
</refsect1>
</refentry>
<!--
-$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
-->
<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>
- <para>
- <variablelist>
- <varlistentry>
- <term><replaceable class="parameter">table</replaceable></term>
- <listitem>
- <para>
- The name (optionally schema-qualified) of an existing table.
- </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.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
-
- <refsect2 id="R2-SQL-DELETE-2">
- <refsect2info>
- <date>1998-04-15</date>
- </refsect2info>
- <title>
- Outputs
- </title>
- <para>
- <variablelist>
- <varlistentry>
- <term><computeroutput>
-DELETE <replaceable class="parameter">count</replaceable>
- </computeroutput></term>
- <listitem>
- <para>
- Message returned if items 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.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-DELETE-1">
- <refsect1info>
- <date>1998-04-15</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <title>Description</title>
<para>
- <command>DELETE</command> removes rows which satisfy the WHERE
- clause from the specified table.
+ <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>
- <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
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.
+ 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 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>.
+ 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 id="R1-SQL-DELETE-2">
- <title>
- Usage
- </title>
+ <refsect1>
+ <title>Parameters</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><replaceable class="parameter">table</replaceable></term>
+ <listitem>
+ <para>
+ The name (optionally schema-qualified) of an existing table.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="parameter">condition</replaceable></term>
+ <listitem>
+ <para>
+ 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>
+ </refsect1>
+
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><computeroutput>DELETE <replaceable class="parameter">count</replaceable></computeroutput></term>
+ <listitem>
+ <para>
+ Message returned if rows are successfully deleted. The
+ <replaceable class="parameter">count</replaceable> is the number
+ of rows deleted. If <replaceable
+ class="parameter">count</replaceable> is 0, no rows were
+ deleted.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+
<para>
- Remove all films but musicals:
+ Delete all films but musicals:
<programlisting>
DELETE FROM films WHERE kind <> '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>
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>
-
- where <replaceable class="parameter">cursor</replaceable>
- identifies an open cursor.
- Interactive cursors in <productname>PostgreSQL</productname> are read-only.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ This command conforms to the SQL standard.
+ </para>
</refsect1>
</refentry>
<!--
-$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
-->
<refentrytitle id="SQL-END-TITLE">END</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
+
<refnamediv>
- <refname>
- END
- </refname>
- <refpurpose>
- commit the current transaction
- </refpurpose>
- </refnamediv>
-
+ <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>
- <para>
-
- <variablelist>
- <varlistentry>
- <term>WORK</term>
- <term>TRANSACTION</term>
- <listitem>
- <para>
- Optional keywords. 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>
-
- <variablelist>
- <varlistentry>
- <term><computeroutput>
-COMMIT
- </computeroutput></term>
- <listitem>
- <para>
- Message returned if the transaction is successfully committed.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><computeroutput>
-WARNING: COMMIT: no transaction in progress
- </computeroutput></term>
- <listitem>
- <para>
- If there is no transaction in progress.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-END-1">
- <refsect1info>
- <date>1998-09-08</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <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">.
+ <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>
- <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>Parameters</title>
- <para>
- Use <xref linkend="SQL-ROLLBACK" endterm="SQL-ROLLBACK-TITLE">
- to abort a transaction.
- </para>
- </refsect2>
+ <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>COMMIT</computeroutput></term>
+ <listitem>
+ <para>
+ Message returned if the transaction was successfully committed.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>WARNING: COMMIT: no transaction in progress</computeroutput></term>
+ <listitem>
+ <para>
+ Message if there is no transaction in progress.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
- <refsect1 id="R1-SQL-END-2">
- <title>
- Usage
- </title>
<para>
- To make all changes permanent:
+ Use <xref linkend="SQL-ROLLBACK" endterm="SQL-ROLLBACK-TITLE"> to
+ abort a transaction.
+ </para>
+ </refsect1>
+
+ <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>
- <para>
- <command>END</command> is a <productname>PostgreSQL</productname>
- extension which provides functionality equivalent to
- <xref linkend="sql-commit" endterm="sql-commit-title">.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ <command>END</command> is a <productname>PostgreSQL</productname>
+ extension that provides functionality equivalent to <xref
+ linkend="sql-commit" endterm="sql-commit-title">, which is
+ specified in the SQL standard.
+ </para>
</refsect1>
</refentry>
<!--
-$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
-->
<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>
-
- <refsect2 id="R2-SQL-EXECUTE-1">
- <refsect2info>
- <date>2002-08-12</date>
- </refsect2info>
- <title>
- Inputs
- </title>
-
- <para>
- <variablelist>
- <varlistentry>
- <term><replaceable class="PARAMETER">plan_name</replaceable></term>
- <listitem>
- <para>
- The name of the prepared query to execute.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <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.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <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).
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+ <refsynopsisdiv>
+<synopsis>
+EXECUTE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable class="PARAMETER">parameter</replaceable> [, ...] ) ] [ INTO [ TEMPORARY | TEMP ] <replaceable class="PARAMETER">table</replaceable> ]
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-EXECUTE-1">
- <refsect1info>
- <date>2002-08-12</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <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
+ 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 query
+ 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 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.
+ 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>
<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,
+ 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 queries,
+ For more information on the creation and usage of prepared statements,
see <xref linkend="sql-prepare" endterm="sql-prepare-title">.
</para>
</refsect1>
- <refsect1 id="R1-SQL-EXECUTE-2">
- <title>
- Compatibility
- </title>
+ <refsect1>
+ <title>Parameters</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><replaceable class="PARAMETER">plan_name</replaceable></term>
+ <listitem>
+ <para>
+ The name of the prepared statement to execute.
+ </para>
+ </listitem>
+ </varlistentry>
- <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.
- </para>
- </refsect2>
+ <varlistentry>
+ <term><replaceable class="PARAMETER">parameter</replaceable></term>
+ <listitem>
+ <para>
+ 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>
+
+ <varlistentry>
+ <term><replaceable class="PARAMETER">table</replaceable></term>
+ <listitem>
+ <para>
+ 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>
+ </refsect1>
+
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ 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>
</refsect1>
</refentry>
<!--
-$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
-->
<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>
- <para>
-
- <variablelist>
- <varlistentry>
- <term>ANALYZE</term>
- <listitem>
- <para>
- Flag to carry out the query and show actual run times.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>VERBOSE</term>
- <listitem>
- <para>
- Flag to show detailed query plan dump.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><replaceable class="PARAMETER">query</replaceable></term>
- <listitem>
- <para>
- Any <command>SELECT</>, <command>INSERT</>, <command>UPDATE</>,
- <command>DELETE</>, <command>EXECUTE</>,
- or <command>DECLARE CURSOR</> query.
- </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>
- <listitem>
- <para>
- Explicit query plan from the <productname>PostgreSQL</productname>
- planner.
- </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>
+<synopsis>
+EXPLAIN [ ANALYZE ] [ VERBOSE ] <replaceable class="parameter">statement</replaceable>
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-EXPLAIN-1">
- <refsect1info>
- <date>1998-04-15</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <title>Description</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,
+ 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 tuples from
+ algorithms will be used to bring together the required row from
each input table.
</para>
<para>
- The most critical part of the display is the estimated query execution
+ 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
- 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
+ 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 tuple, anyway).
- Also, if you limit the number of tuples to return with a LIMIT clause,
+ (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>
- <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.
- </para>
- </note>
-
<para>
- The ANALYZE option causes the query to be actually executed, not only
+ 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>
- <caution>
+ <important>
<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>
+ 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>
+</programlisting>
</para>
- </caution>
+ </important>
+ </refsect1>
+
+ <refsect1>
+ <title>Parameter</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><literal>ANALYZE</literal></term>
+ <listitem>
+ <para>
+ Carry out the command and show the actual run times.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>VERBOSE</literal></term>
+ <listitem>
+ <para>
+ 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>
+
+ <varlistentry>
+ <term><replaceable class="parameter">statement</replaceable></term>
+ <listitem>
+ <para>
+ 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>
+ </refsect1>
+
+ <refsect1>
+ <title>Diagnostics</title>
<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.
+ <command>EXPLAIN</command> prints the execution plan of the
+ specified statement from the <productname>PostgreSQL</productname>
+ planner.
</para>
+ </refsect1>
- <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.
- </para>
- </refsect2>
+ <refsect1>
+ <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.
+ </para>
+
+ <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.
+ </para>
+
+ <para>
+ 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>
</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>
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>
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>
EXPLAIN SELECT sum(i) FROM foo WHERE i < 10;
- <computeroutput>
+
QUERY PLAN
---------------------------------------------------------------------
Aggregate (cost=23.93..23.93 rows=1 width=4)
-> Index Scan using fi on foo (cost=0.00..23.92 rows=6 width=4)
Index Cond: (i < 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>
PREPARE query(int, int) AS SELECT sum(bar) FROM test
WHERE id > $1 AND id < $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)
Index Cond: ((id > $1) AND (id < $2))
Total runtime: 0.85 msec
(4 rows)
- </computeroutput>
- </programlisting>
+</programlisting>
</para>
<para>
- Note that the specific numbers shown, and even the selected query
- strategy, may vary between <productname>PostgreSQL</productname>
- releases due to planner improvements. In addition, the
- <command>ANALYZE</command> command uses random sampling to estimate
- data statistics; therefore, it is possible
- for cost estimates to change after a fresh run of
+ Of course, the specific numbers shown here depend on the actual
+ contents of the tables involved. Also note that the numbers, and
+ even the selected query strategy, may vary between
+ <productname>PostgreSQL</productname> releases due to planner
+ improvements. In addition, the <command>ANALYZE</command> command
+ uses random sampling to estimate data statistics; therefore, it is
+ possible for cost estimates to change after a fresh run of
<command>ANALYZE</command>, even if the actual distribution of data
in the table has not changed.
</para>
</refsect1>
- <refsect1 id="R1-SQL-EXPLAIN-3">
- <title>
- Compatibility
- </title>
-
- <refsect2 id="R2-SQL-EXPLAIN-4">
- <refsect2info>
- <date>1998-09-01</date>
- </refsect2info>
- <title>
- SQL92
- </title>
- <para>
- There is no <command>EXPLAIN</command> statement defined in SQL92.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ There is no <command>EXPLAIN</command> statement defined in the SQL standard.
+ </para>
</refsect1>
</refentry>
<!--
-$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
-->
<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>
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>
<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.)
</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
</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
<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
<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;
<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>
<!--
-$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
-->
<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>
-
- <refsect2 id="R2-SQL-INSERT-1">
- <title>
- Inputs
- </title>
-
- <para>
-
- <variablelist>
- <varlistentry>
- <term><replaceable class="PARAMETER">table</replaceable></term>
- <listitem>
- <para>
- The name (optionally schema-qualified) of an existing table.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><replaceable class="PARAMETER">column</replaceable></term>
- <listitem>
- <para>
- The name of a column in <replaceable class="PARAMETER">table</replaceable>.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>DEFAULT VALUES</term>
- <listitem>
- <para>
- All columns will be filled by null values or by values specified
- when the table was created using <literal>DEFAULT</> clauses.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><replaceable class="PARAMETER">expression</replaceable></term>
- <listitem>
- <para>
- A valid expression or value to assign to <replaceable
- class="PARAMETER">column</replaceable>.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><replaceable class="PARAMETER">DEFAULT</replaceable></term>
- <listitem>
- <para>
- This column will be filled in by the column DEFAULT clause, or NULL if
- a default is not available.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><replaceable class="PARAMETER">query</replaceable></term>
- <listitem>
- <para>
- A valid query. Refer to the SELECT statement for a further description
- of valid arguments.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
-
- <refsect2 id="R2-SQL-INSERT-2">
- <title>
- Outputs
- </title>
- <para>
-
- <variablelist>
- <varlistentry>
- <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.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><computeroutput>
-INSERT 0 <replaceable>#</replaceable>
- </computeroutput></term>
- <listitem>
- <para>
- Message returned if more than one rows were inserted.
- <returnvalue><replaceable>#</replaceable></returnvalue>
- is the number of rows inserted.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+ { DEFAULT VALUES | VALUES ( { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...] ) | <replaceable class="PARAMETER">query</replaceable> }
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-INSERT-1">
- <title>
- Description
- </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.
- The columns in the target list may be listed in any order.
</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. <productname>PostgreSQL</productname> will reject the new
- column if a NULL is inserted into a column declared NOT NULL.
+ 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 coercion will be
- attempted.
+ If the expression for each column is not of the correct data type,
+ automatic type conversion 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.
+ 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 id="R1-SQL-INSERT-2">
- <title>
- Usage
- </title>
+ <refsect1>
+ <title>Parameters</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><replaceable class="PARAMETER">table</replaceable></term>
+ <listitem>
+ <para>
+ The name (optionally schema-qualified) of an existing table.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="PARAMETER">column</replaceable></term>
+ <listitem>
+ <para>
+ The name of a column in <replaceable class="PARAMETER">table</replaceable>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>DEFAULT VALUES</literal></term>
+ <listitem>
+ <para>
+ All columns will be filled their default values.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="PARAMETER">expression</replaceable></term>
+ <listitem>
+ <para>
+ An expression or value to assign to <replaceable
+ class="PARAMETER">column</replaceable>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>DEFAULT</literal></term>
+ <listitem>
+ <para>
+ This column will be filled with its default value.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="PARAMETER">query</replaceable></term>
+ <listitem>
+ <para>
+ 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>
+ </refsect1>
+
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <variablelist>
+ <varlistentry>
+ <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
+ <acronym>OID</acronym> of the inserted row.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>INSERT 0 <replaceable>count</replaceable></computeroutput></term>
+ <listitem>
+ <para>
+ Message returned if more than one rows were inserted.
+ <replaceable>count</replaceable> is the number of rows inserted.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+
<para>
Insert a single row into table <literal>films</literal>:
+<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>
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>
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>
INSERT INTO films SELECT * FROM tmp;
- </programlisting>
+</programlisting>
</para>
<para>
- Insert into arrays:
+ This example inserts into array columns:
+<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>
-
- <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
- <xref linkend="sql-select" endterm="sql-select-title">.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ <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>
</refsect1>
</refentry>
<!--
-$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
-->
<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>
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>
-
- <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.
- </para>
- <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.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <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>
+ Message returned if this session is already registered for that notification condition.
+ </para>
+ </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>
- <para>
- There is no <command>LISTEN</command> in <acronym>SQL92</acronym>.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ There is no <command>LISTEN</command> statement in the SQL
+ standard.
+ </para>
</refsect1>
</refentry>
<!--
-$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">
<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.
<!--
-$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
-->
<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>
-
- <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>
-
- <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.
- </para>
-
- <note>
- <para>
- Acquired by <command>VACUUM</command> (without
- <option>FULL</option>).
- </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.
- </para>
-
- <note>
- <para>
- Acquired by <command>CREATE INDEX</command>.
- </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.
- </para>
-
- <note>
- <para>
- This lock mode is not automatically acquired by any
- <productname>PostgreSQL</productname> command.
- </para>
- </note>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>EXCLUSIVE MODE</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.
- </para>
-
- <note>
- <para>
- This lock mode is not automatically acquired by any
- <productname>PostgreSQL</productname> command.
- </para>
- </note>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>ACCESS EXCLUSIVE MODE</term>
- <listitem>
- <para>
- Conflicts with all lock modes. This mode guarantees that the
- holder is the only transaction accessing the table in any way.
- </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.
- </para>
- </note>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
-
- <refsect2 id="R2-SQL-LOCK-2">
- <refsect2info>
- <date>1998-09-24</date>
- </refsect2info>
- <title>
- Outputs
- </title>
- <para>
-
- <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>
- <listitem>
- <para>
- Message returned if <replaceable class="PARAMETER">name</replaceable>
- does not exist.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+ ACCESS SHARE | ROW SHARE | ROW EXCLUSIVE | SHARE UPDATE EXCLUSIVE
+ | SHARE | SHARE ROW EXCLUSIVE | EXCLUSIVE | ACCESS EXCLUSIVE
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-LOCK-1">
- <refsect1info>
- <date>1998-09-24</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <title>Description</title>
<para>
<command>LOCK TABLE</command> obtains a table-level lock, waiting if
</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>
+ 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
+ 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 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>
+ 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>
-
+
<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.)
+ 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>
<para>
- Two general rules may be followed to prevent deadlock conditions:
+ 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>
- <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.
+ More information about the lock modes and locking strategies can be
+ found in <xref linkend="explicit-locking">.
</para>
+ </refsect1>
- <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>
+ <title>Parameters</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><replaceable class="PARAMETER">name</replaceable></term>
+ <listitem>
+ <para>
+ The name (optionally schema-qualified) of an existing table to
+ lock.
+ </para>
+
+ <para>
+ 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>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="parameter">lockmode</replaceable></term>
+ <listitem>
+ <para>
+ The lock mode specifies which locks this lock conflicts with.
+ Lock modes are described in <xref linkend="explicit-locking">.
+ </para>
+
+ <para>
+ If no lock mode is specified, then <literal>ACCESS
+ EXCLUSIVE</literal>, the most restrictive mode, is used.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
- <refsect2 id="R2-SQL-LOCK-3">
- <refsect2info>
- <date>1999-06-08</date>
- </refsect2info>
- <title>
- Notes
- </title>
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><computeroutput>LOCK TABLE</computeroutput></term>
+ <listitem>
+ <para>
+ Message returned if the lock was successfully acquired.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
<para>
<literal>LOCK ... IN ACCESS SHARE MODE</> requires <literal>SELECT</>
<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.
- </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>
+ <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>
-
- <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>
BEGIN WORK;
LOCK TABLE films IN SHARE MODE;
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>
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>,
- 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.
- </para>
+ <para>
+ There is no <command>LOCK TABLE</command> in the SQL standard,
+ which instead uses <command>SET TRANSACTION</command> to specify
+ concurrency levels on transactions. PostgreSQL supports that too;
+ see <xref linkend="SQL-SET-TRANSACTION"
+ endterm="SQL-SET-TRANSACTION-TITLE"> for details.
+ </para>
- Except for ACCESS SHARE, ACCESS EXCLUSIVE, and 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).
- </para>
- </refsect2>
+ <para>
+ 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>.
+ </para>
</refsect1>
</refentry>
<!--
-$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
-->
<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>
-
- <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>
-
- <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.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-NOTIFY-1">
- <refsect1info>
- <date>1998-10-07</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <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.
+ 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>
+
<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
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.)
+ 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>
+ Name of the notification to be signaled (any identifier).
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Diagnostics</title>
- <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.
- </para>
- <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.
- </para>
- <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.
- </para>
- </refsect2>
+ <variablelist>
+ <varlistentry>
+ <term><computeroutput>NOTIFY</computeroutput></term>
+ <listitem>
+ <para>
+ Message returned when the commmand has executed.
+ </para>
+ </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>:
</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>
- <para>
- There is no <command>NOTIFY</command> statement in
- <acronym>SQL92</acronym>.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ There is no <command>NOTIFY</command> statement in the SQL
+ standard.
+ </para>
</refsect1>
</refentry>
<!--
-$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
-->
<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>
-
- <para>
- <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.
- </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.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><replaceable class="PARAMETER">query</replaceable></term>
- <listitem>
- <para>
- Any <command>SELECT</>, <command>INSERT</>, <command>UPDATE</>,
- or <command>DELETE</> query.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
-
- <refsect2 id="R2-SQL-PREPARE-2">
- <refsect2info>
- <date>2002-08-12</date>
- </refsect2info>
- <title>
- Outputs
- </title>
- <para>
-
- <variablelist>
- <varlistentry>
- <term><computeroutput>
- <returnvalue>PREPARE</returnvalue>
- </computeroutput></term>
- <listitem>
- <para>
- The query has been prepared successfully.
- </para>
- </listitem>
- </varlistentry>
-
- </variablelist>
- </para>
- </refsect2>
+<synopsis>
+PREPARE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable class="PARAMETER">datatype</replaceable> [, ...] ) ] AS <replaceable class="PARAMETER">statement</replaceable>
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-PREPARE-1">
- <refsect1info>
- <date>2002-08-12</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <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
+ <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 query is parsed, rewritten, and
- planned. When a subsequent <command>EXECUTE</command> statement is
- issued, the prepared query need only be executed. Thus, the
+ 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 query is executed.
+ instead of every time the statement 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
+ 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 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.
+ 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 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
+ 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 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
+ 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 query is relatively simple
+ 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 queries will be less noticeable.
+ performance advantage of prepared statements will be less noticeable.
</para>
+ </refsect1>
- <refsect2 id="R2-SQL-PREPARE-3">
- <refsect2info>
- <date>2002-08-12</date>
- </refsect2info>
- <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
- 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
- <productname>PostgreSQL</productname> has chosen for a prepared
- query, 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.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Parameters</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><replaceable class="PARAMETER">plan_name</replaceable></term>
+ <listitem>
+ <para>
+ 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 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">statement</replaceable></term>
+ <listitem>
+ <para>
+ Any <command>SELECT</>, <command>INSERT</>, <command>UPDATE</>,
+ or <command>DELETE</> statement.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
</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>
- <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.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><computeroutput>PREPARE</computeroutput></term>
+ <listitem>
+ <para>
+ Message returned if the statement has been prepared successfully.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>
+ 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 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
+ statement, use <command>EXPLAIN EXECUTE</command>.
+ </para>
+
+ <para>
+ 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>
+ </refsect1>
+
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ 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>
</refsect1>
</refentry>
<!--
-$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
-->
<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.
<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>.
+ 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>. 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>
- <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>
-
<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.
+ 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>
- Since this is likely the only situation when most people will ever use
- a standalone backend, some usage notes might be in order:
+ See the <xref linkend="app-postgres"> reference page for more
+ information about how to interact with the stand-alone server
+ interface.
+ </para>
+ </refsect1>
+
+ <refsect1>
+ <title>Parameters</title>
- <itemizedlist>
+ <variablelist>
+ <varlistentry>
+ <term><literal>DATABASE</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 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>
+ <varlistentry>
+ <term><literal>TABLE</literal></term>
<listitem>
<para>
- You can issue any SQL command, not only <command>REINDEX</>.
+ Recreate all indexes of a specified table.
</para>
</listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><literal>INDEX</literal></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).
+ Recreate a specified index.
</para>
</listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><replaceable class="PARAMETER">name</replaceable></term>
<listitem>
<para>
- To quit the backend, type <acronym>EOF</> (<keycombo
- action="simul"><keycap>Control</><keycap>D</></>, usually).
+ The name of the specific database, table, or index to be
+ reindexed. Table and index names may be schema-qualified.
</para>
</listitem>
+ </varlistentry>
- </itemizedlist>
+ <varlistentry>
+ <term><literal>FORCE</literal></term>
+ <listitem>
+ <para>
+ 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>
+
+ <refsect1>
+ <title>Diagnostics</title>
- See the <xref linkend="app-postgres"> reference page for more information.
- </para>
+ <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>:
- REINDEX TABLE mytable;
- </programlisting>
+<programlisting>
+REINDEX TABLE my_table;
+</programlisting>
</para>
<para>
Rebuild a single index:
- 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):
- REINDEX DATABASE my_database FORCE;
- </programlisting>
+<programlisting>
+REINDEX DATABASE my_database FORCE;
+</programlisting>
</para>
</refsect1>
- <refsect1 id="R1-SQL-REINDEX-3">
- <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>.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ There is no <command>REINDEX</command> command in the SQL standard.
+ </para>
</refsect1>
</refentry>
<!--
-$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
-->
<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>
<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 }
One of <literal>RESTRICT</literal> or <literal>CASCADE</literal>
is required.
</para>
- </refsect2>
</refsect1>
<refsect1>
<!--
-$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
-->
<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>
- <para>
- None.
- </para>
- </refsect2>
-
- <refsect2 id="R2-SQL-ROLLBACK-2">
- <refsect2info>
- <date>1998-09-24</date>
- </refsect2info>
- <title>
- Outputs
- </title>
- <para>
-
- <variablelist>
- <varlistentry>
- <term><computeroutput>
-ROLLBACK
- </computeroutput></term>
- <listitem>
- <para>
- Message returned if successful.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>
-WARNING: ROLLBACK: no transaction in progress
- </computeroutput></term>
- <listitem>
- <para>
- If there is not any transaction currently in progress.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-ROLLBACK-1">
- <refsect1info>
- <date>1998-09-24</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <title>Description</title>
<para>
<command>ROLLBACK</command> rolls back the current transaction and causes
all the updates made by the transaction to be discarded.
</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Parameters</title>
- <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>.
- </para>
- </refsect2>
+ <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 id="R1-SQL-ROLLBACK-2">
- <title>
- Usage
- </title>
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><computeroutput>ROLLBACK</computeroutput></term>
+ <listitem>
+ <para>
+ Message returned if successful.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>WARNING: ROLLBACK: no transaction in progress</computeroutput></term>
+ <listitem>
+ <para>
+ If there is not any transaction currently in progress.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
<para>
- To abort all changes:
+ Use <xref linkend="SQL-COMMIT" endterm="SQL-COMMIT-TITLE"> to
+ successfully terminate a transaction.
+ </para>
+ </refsect1>
- <programlisting>
-ROLLBACK WORK;
- </programlisting>
+ <refsect1>
+ <title>Examples</title>
+
+ <para>
+ To abort all changes:
+<programlisting>
+ROLLBACK;
+</programlisting>
</para>
</refsect1>
- <refsect1 id="R1-SQL-ROLLBACK-3">
- <title>
- Compatibility
- </title>
+ <refsect1>
+ <title>Compatibility</title>
- <refsect2 id="R2-SQL-ROLLBACK-4">
- <refsect2info>
- <date>1998-09-24</date>
- </refsect2info>
- <title>
- SQL92
- </title>
- <para>
- <acronym>SQL92</acronym> only specifies the two forms <literal>ROLLBACK</literal>
- and <literal>ROLLBACK WORK</literal>. Otherwise full compatibility.
- </para>
- </refsect2>
+ <para>
+ The SQL standard only specifies the two forms
+ <literal>ROLLBACK</literal> and <literal>ROLLBACK
+ WORK</literal>. Otherwise, this command is fully conforming.
+ </para>
</refsect1>
</refentry>
<!--
-$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>
</refnamediv>
<refsynopsisdiv>
- <synopsis>
+<synopsis>
START TRANSACTION [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
- </synopsis>
-
- <refsect2 id="R2-SQL-START-TRANSACTION-1">
- <refsect2info>
- <date>1998-09-27</date>
- </refsect2info>
- <title>
- Inputs
- </title>
-
- <para>
- None.
- </para>
- </refsect2>
-
- <refsect2 id="R2-SQL-START-TRANSACTION-2">
- <refsect2info>
- <date>1998-09-27</date>
- </refsect2info>
- <title>
- Outputs
- </title>
-
- <para>
-
- <variablelist>
- <varlistentry>
- <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>
- <listitem>
- <para>
- If there is already a transaction in progress when the
- command is issued.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+</synopsis>
</refsynopsisdiv>
<refsect1>
respects, the behavior of this command is identical to the <xref
linkend="sql-begin" endterm="sql-begin-title"> command.
</para>
+ </refsect1>
+
+ <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>
+ <listitem>
+ <para>
+ Message returned if successful.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>WARNING: BEGIN: already a transaction in progress</computeroutput></term>
+ <listitem>
+ <para>
+ Message returned if there was already a transaction in progress
+ when the command was issued.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
</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>
<!--
-$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
-->
<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>
-
- <refsect2 id="R2-SQL-TRUNCATE-1">
- <refsect2info>
- <date>1998-09-08</date>
- </refsect2info>
- <title>
- Inputs
- </title>
- <para>
-
- <variablelist>
- <varlistentry>
- <term><replaceable class="PARAMETER">name</replaceable></term>
- <listitem>
- <para>
- The name (optionally schema-qualified) of the table to be truncated.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
-
- <refsect2 id="R2-SQL-TRUNCATE-2">
- <refsect2info>
- <date>1998-09-08</date>
- </refsect2info>
- <title>
- Outputs
- </title>
- <para>
-
- <variablelist>
- <varlistentry>
- <term><computeroutput>
-TRUNCATE TABLE
- </computeroutput></term>
- <listitem>
- <para>
- Message returned if the table is successfully truncated.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-TRUNCATE-1">
- <refsect1info>
- <date>1998-09-08</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <title>Description</title>
+
<para>
<command>TRUNCATE</command> quickly removes all rows from a
table. It has the same effect as an unqualified
table it is faster. This is most useful on large tables.
</para>
</refsect1>
+
+ <refsect1>
+ <title>Parameter</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><replaceable class="PARAMETER">name</replaceable></term>
+ <listitem>
+ <para>
+ The name (optionally schema-qualified) of the table to be truncated.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><computeroutput>TRUNCATE TABLE</computeroutput></term>
+ <listitem>
+ <para>
+ Message returned if the table was successfully truncated.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
- <refsect1 id="R1-SQL-TRUNCATE-2">
- <title>
- Usage
- </title>
<para>
Truncate the table <literal>bigtable</literal>:
+<programlisting>
TRUNCATE TABLE bigtable;
- </programlisting>
+</programlisting>
</para>
</refsect1>
- <refsect1 id="R1-SQL-TRUNCATE-3">
- <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>.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ There is no <command>TRUNCATE</command> command in the SQL standard.
+ </para>
</refsect1>
</refentry>
<!--
-$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
-->
<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>
-
- <para>
- <variablelist>
- <varlistentry>
- <term><replaceable class="PARAMETER">notifyname</replaceable></term>
- <listitem>
- <para>
- Name of previously registered notify condition.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><literal>*</literal></term>
- <listitem>
- <para>
- All current listen registrations for this backend 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>
-
- <variablelist>
- <varlistentry>
- <term><computeroutput>
-<returnvalue>UNLISTEN</returnvalue>
- </computeroutput></term>
- <listitem>
- <para>
- Acknowledgment that statement has executed.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+<synopsis>
+UNLISTEN { <replaceable class="PARAMETER">name</replaceable> | * }
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-UNLISTEN-1">
- <refsect1info>
- <date>1998-10-19</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <title>Description</title>
<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.
+ <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>
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 notification (any identifier).
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>*</literal></term>
+ <listitem>
+ <para>
+ All current listen registrations for this session are cleared.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><computeroutput>UNLISTEN</computeroutput></term>
+ <listitem>
+ <para>
+ Message returned when the command has executed.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>
+ 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.
- </para>
- </refsect2>
+ <para>
+ At the end of each session, <command>UNLISTEN *</command> ist
+ automatically executed.
+ </para>
</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>
<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>
- <para>
- There is no <command>UNLISTEN</command> in <acronym>SQL92</acronym>.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ There is no <command>UNLISTEN</command> command in the SQL standard.
+ </para>
</refsect1>
</refentry>
<!--
-$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
-->
<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>
- <para>
-
- <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.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><replaceable class="PARAMETER">column</replaceable></term>
- <listitem>
- <para>
- The name of a column in <replaceable class="PARAMETER">table</replaceable>.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><replaceable class="PARAMETER">expression</replaceable></term>
- <listitem>
- <para>
- A valid expression or value to assign to 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.
- </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.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
-
- <refsect2 id="R2-SQL-UPDATE-2">
- <refsect2info>
- <date>1998-09-24</date>
- </refsect2info>
- <title>
- Outputs
- </title>
-
- <para>
- <variablelist>
- <varlistentry>
- <term><computeroutput>
-UPDATE <replaceable class="parameter">#</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.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+</synopsis>
</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>
+ <refsect1>
+ <title>Description</title>
<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.
+ <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>
- 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.
+ 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>
- 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.
+ 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 id="R1-SQL-UPDATE-2">
- <title>
- Usage
- </title>
+ <refsect1>
+ <title>Parameters</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><replaceable class="PARAMETER">table</replaceable></term>
+ <listitem>
+ <para>
+ The name (optionally schema-qualified) of the table to update.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="PARAMETER">column</replaceable></term>
+ <listitem>
+ <para>
+ The name of a column in <replaceable class="PARAMETER">table</replaceable>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="PARAMETER">expression</replaceable></term>
+ <listitem>
+ <para>
+ An expression or value to assign to the column.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="PARAMETER">fromlist</replaceable></term>
+ <listitem>
+ <para>
+ 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>
+ 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>
+ </refsect1>
+
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><computeroutput>UPDATE <replaceable class="parameter">count</replaceable></computeroutput></term>
+ <listitem>
+ <para>
+ 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>
+ </refsect1>
+
+ <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>
-
- where <replaceable class="parameter">cursor</replaceable>
- identifies an open cursor.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ This command conforms to the SQL standard. The
+ <literal>FROM</literal> clause is a PostgreSQL extension.
+ </para>
</refsect1>
</refentry>
<!--
-$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
-->
<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>
-
- <refsect2 id="R2-SQL-VACUUM-1">
- <refsect2info>
- <date>2001-07-10</date>
- </refsect2info>
- <title>
- Inputs
- </title>
-
- <para>
- <variablelist>
- <varlistentry>
- <term>FULL</term>
- <listitem>
- <para>
- 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>
- <listitem>
- <para>
- Selects aggressive <quote>freezing</quote> of tuples.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>VERBOSE</term>
- <listitem>
- <para>
- Prints a detailed vacuum activity report for each table.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>ANALYZE</term>
- <listitem>
- <para>
- Updates statistics used by the optimizer to
- determine the most efficient way to execute a query.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><replaceable class="PARAMETER">table</replaceable></term>
- <listitem>
- <para>
- The name (optionally schema-qualified) of a specific table to
- vacuum. Defaults to all tables in the current database.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><replaceable class="PARAMETER">column</replaceable></term>
- <listitem>
- <para>
- The name of a specific column to analyze. Defaults to all columns.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
-
- <refsect2 id="R2-SQL-VACUUM-2">
- <refsect2info>
- <date>1998-10-04</date>
- </refsect2info>
- <title>
- Outputs
- </title>
- <para>
-
- <variablelist>
- <varlistentry>
- <term><computeroutput>
-<returnvalue>VACUUM</returnvalue>
- </computeroutput></term>
- <listitem>
- <para>
- The command is complete.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>
-INFO: --Relation <replaceable class="PARAMETER">table</replaceable>--
- </computeroutput></term>
- <listitem>
- <para>
- The report header for <replaceable class="PARAMETER">table</replaceable>.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <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>
- <listitem>
- <para>
- The analysis for <replaceable class="PARAMETER">table</replaceable> itself.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <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.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </refsect2>
+</synopsis>
</refsynopsisdiv>
- <refsect1 id="R1-SQL-VACUUM-1">
- <refsect1info>
- <date>2001-07-10</date>
- </refsect1info>
- <title>
- Description
- </title>
+ <refsect1>
+ <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
+ 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.
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.
+ 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><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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>FREEZE</literal></term>
+ <listitem>
+ <para>
+ Selects aggressive <quote>freezing</quote> of tuples.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>VERBOSE</literal></term>
+ <listitem>
+ <para>
+ Prints a detailed vacuum activity report for each table.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>ANALYZE</literal></term>
+ <listitem>
+ <para>
+ 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>
+ <para>
+ The name (optionally schema-qualified) of a specific table to
+ vacuum. Defaults to all tables in the current database.
+ </para>
+ </listitem>
+ </varlistentry>
- <refsect2 id="R2-SQL-VACUUM-3">
- <refsect2info>
- <date>2001-07-10</date>
- </refsect2info>
- <title>
- Notes
- </title>
+ <varlistentry>
+ <term><replaceable class="PARAMETER">column</replaceable></term>
+ <listitem>
+ <para>
+ The name of a specific column to analyze. Defaults to all columns.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><computeroutput>VACUUM</computeroutput></term>
+ <listitem>
+ <para>
+ The command is complete.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>INFO: --Relation <replaceable class="PARAMETER">table</replaceable>--</computeroutput></term>
+ <listitem>
+ <para>
+ The report header for <replaceable class="PARAMETER">table</replaceable>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <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>
+ <listitem>
+ <para>
+ The analysis for <replaceable class="PARAMETER">table</replaceable> itself.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <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.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <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>
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:
-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.
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>
- <para>
- There is no <command>VACUUM</command> statement in <acronym>SQL92</acronym>.
- </para>
- </refsect2>
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ There is no <command>VACUUM</command> statement in the SQL standard.
+ </para>
</refsect1>
<refsect1>
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