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Documentation of the system catalogs, directed toward PostgreSQL developers

$Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.56 2002/08/30 19:23:18 tgl Exp $

$Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.57 2002/09/02 05:44:43 momjian Exp $

-->

<chapter id="catalogs">

<entry>database users</entry>

</row>

<row>

<entry>pg_settings</entry>

<entry>current session run-time parameters</entry>

</row>

<row>

<entry>pg_statistic</entry>

<entry>optimizer statistics</entry>

</sect1>

<sect1 id="catalog-pg-settings">

<title>pg_settings</title>

<para>

<structname>pg_settings</structname> virtual table allows display and update

of current session run-time parameters. There is one entry for each of the

available parameters provided by <command>SHOW ALL</command>. But it is

in a form that allows it to be joined with other relations and have a

selection criteria applied.

</para>

<para>

An <command>UPDATE</command> performed on <structname>pg_settings</structname>

is equivalent to executing the <command>SET</command> command on that named

parameter. The change only affects the value used by the current session. If

an <command>UPDATE</command> is issued within a transaction that is later

aborted, the effects of the <command>UPDATE</command> command disappear when

the transaction is rolled back. Once the surrounding transaction is

committed, the effects will persist until the end of the session, unless

overridden by another <command>UPDATE</command> or <command>SET</command>.

</para>

<table>

<title>pg_settings Columns</title>

<tgroup cols=4>

<thead>

<row>

<entry>Name</entry>

<entry>Type</entry>

<entry>References</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry>name</entry>

<entry><type>text</type></entry>

<entry></entry>

<entry>The name of a current session run-time parameter</entry>

</row>

<row>

<entry>setting</entry>

<entry><type>text</type></entry>

<entry></entry>

<entry>The value of a current session run-time parameter</entry>

</row>

</tbody>

</tgroup>

</table>

</sect1>

<sect1 id="catalog-pg-statistic">

<title>pg_statistic</title>