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transaction, unless rolled back or overridden by a SET clause for the same variable attached to a surrounding function call. Per discussion, these seem the best semantics. Note that this is an INCOMPATIBLE CHANGE: in 8.0 through 8.2, SET LOCAL's effects disappeared at subtransaction commit (leading to behavior that made little sense at the SQL level). I took advantage of the opportunity to rewrite and simplify the GUC variable save/restore logic a little bit. The old idea of a "tentative" value is gone; it was a hangover from before we had a stack. Also, we no longer need a stack entry for every nesting level, but only for those in which a variable's value actually changed.
114 lines
3.0 KiB
Plaintext
114 lines
3.0 KiB
Plaintext
<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/reset.sgml,v 1.36 2007/09/11 00:06:41 tgl Exp $
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PostgreSQL documentation
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-->
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<refentry id="SQL-RESET">
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<refmeta>
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<refentrytitle id="SQL-RESET-TITLE">RESET</refentrytitle>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>RESET</refname>
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<refpurpose>restore the value of a run-time parameter to the default value</refpurpose>
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</refnamediv>
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<indexterm zone="sql-reset">
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<primary>RESET</primary>
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</indexterm>
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<refsynopsisdiv>
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<synopsis>
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RESET <replaceable class="PARAMETER">configuration_parameter</replaceable>
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RESET ALL
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</synopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<command>RESET</command> restores run-time parameters to their
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default values. <command>RESET</command> is an alternative
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spelling for
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<synopsis>
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SET <replaceable class="parameter">configuration_parameter</replaceable> TO DEFAULT
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</synopsis>
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Refer to <xref linkend="sql-set" endterm="sql-set-title"> for
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details.
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</para>
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<para>
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The default value is defined as the value that the parameter would
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have had, if no <command>SET</> had ever been issued for it in the
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current session. The actual source of this value might be a
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compiled-in default, the configuration file, command-line options,
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or per-database or per-user default settings. This is subtly different
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from defining it as <quote>the value that the parameter had at session
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start</>, because if the value came from the configuration file, it
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will be reset to whatever is specified by the configuration file now.
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See <xref linkend="runtime-config"> for details.
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</para>
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<para>
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The transactional behavior of <command>RESET</> is the same as
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<command>SET</>: its effects will be undone by transaction rollback.
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</para>
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</refsect1>
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<refsect1>
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<title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><replaceable class="PARAMETER">configuration_parameter</replaceable></term>
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<listitem>
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<para>
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Name of a settable run-time parameter. Available parameters are
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documented in <xref linkend="runtime-config"> and on the
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<xref linkend="sql-set" endterm="sql-set-title"> reference page.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>ALL</literal></term>
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<listitem>
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<para>
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Resets all settable run-time parameters to default values.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<para>
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Set the <varname>timezone</> configuration variable to its default value:
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<screen>
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RESET timezone;
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</screen>
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</para>
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</refsect1>
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<refsect1>
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<title>Compatibility</title>
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<para>
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<command>RESET</command> is a <productname>PostgreSQL</productname> extension.
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</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<simplelist type="inline">
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<member><xref linkend="SQL-SET" endterm="SQL-SET-title"></member>
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<member><xref linkend="SQL-SHOW" endterm="SQL-SHOW-title"></member>
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</simplelist>
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</refsect1>
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</refentry>
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