doc/src/sgml/ref/discard.sgml

   1 <!--
   2 $PostgreSQL$
   3 PostgreSQL documentation
   4 -->
   5
   6 <refentry id="SQL-DISCARD">
   7  <refmeta>
   8   <refentrytitle id="SQL-DISCARD-TITLE">DISCARD</refentrytitle>
   9   <manvolnum>7</manvolnum>
  10   <refmiscinfo>SQL - Language Statements</refmiscinfo>
  11  </refmeta>
  12
  13  <refnamediv>
  14   <refname>DISCARD</refname>
  15   <refpurpose>discard session state</refpurpose>
  16  </refnamediv>
  17
  18  <indexterm zone="sql-discard">
  19   <primary>DISCARD</primary>
  20  </indexterm>
  21
  22  <refsynopsisdiv>
  23 <synopsis>
  24 DISCARD { ALL | PLANS | TEMPORARY | TEMP }
  25 </synopsis>
  26  </refsynopsisdiv>
  27
  28  <refsect1>
  29   <title>Description</title>
  30
  31   <para>
  32    <command>DISCARD</> releases internal resources associated with a
  33    database session. These resources are normally released at the end
  34    of the session.
  35   </para>
  36
  37   <para>
  38    <command>DISCARD TEMP</> drops all temporary tables created in the
  39    current session.  <command>DISCARD PLANS</> releases all internally
  40    cached query plans.  <command>DISCARD ALL</> resets a session to
  41    its original state, discarding temporary resources and resetting
  42    session-local configuration changes.
  43   </para>
  44  </refsect1>
  45
  46  <refsect1>
  47   <title>Parameters</title>
  48
  49   <variablelist>
  50
  51    <varlistentry>
  52     <term><literal>TEMPORARY</literal> or <literal>TEMP</literal></term>
  53     <listitem>
  54      <para>
  55       Drops all temporary tables created in the current session.
  56      </para>
  57     </listitem>
  58    </varlistentry>
  59
  60    <varlistentry>
  61     <term><literal>PLANS</literal></term>
  62     <listitem>
  63      <para>
  64       Releases all cached query plans.
  65      </para>
  66     </listitem>
  67    </varlistentry>
  68
  69    <varlistentry>
  70     <term><literal>ALL</literal></term>
  71     <listitem>
  72      <para>
  73       Releases all temporary resources associated with the current
  74       session and resets the session to its initial state.
  75       Currently, this has the same effect as executing the following sequence
  76       of statements:
  77 <programlisting>
  78 SET SESSION AUTHORIZATION DEFAULT;
  79 RESET ALL;
  80 DEALLOCATE ALL;
  81 CLOSE ALL;
  82 UNLISTEN *;
  83 SELECT pg_advisory_unlock_all();
  84 DISCARD PLANS;
  85 DISCARD TEMP;
  86 </programlisting>
  87      </para>
  88     </listitem>
  89    </varlistentry>
  90
  91   </variablelist>
  92  </refsect1>
  93
  94  <refsect1>
  95   <title>Notes</title>
  96
  97    <para>
  98     <command>DISCARD ALL</> cannot be executed inside a transaction block.
  99    </para>
 100  </refsect1>
 101
 102  <refsect1>
 103   <title>Compatibility</title>
 104
 105   <para>
 106    <command>DISCARD</command> is a <productname>PostgreSQL</productname> extension.
 107   </para>
 108  </refsect1>
 109 </refentry>