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Since some preparation work had already been done, the only source changes left were changing empty-element tags like <xref linkend="foo"> to <xref linkend="foo"/>, and changing the DOCTYPE. The source files are still named *.sgml, but they are actually XML files now. Renaming could be considered later. In the build system, the intermediate step to convert from SGML to XML is removed. Everything is build straight from the source files again. The OpenSP (or the old SP) package is no longer needed. The documentation toolchain instructions are updated and are much simpler now. Peter Eisentraut, Alexander Lakhin, Jürgen Purtz
144 lines
4.3 KiB
Plaintext
144 lines
4.3 KiB
Plaintext
<!--
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doc/src/sgml/ref/alter_system.sgml
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PostgreSQL documentation
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-->
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<refentry id="sql-altersystem">
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<indexterm zone="sql-altersystem">
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<primary>ALTER SYSTEM</primary>
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</indexterm>
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<refmeta>
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<refentrytitle>ALTER SYSTEM</refentrytitle>
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<manvolnum>7</manvolnum>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>ALTER SYSTEM</refname>
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<refpurpose>change a server configuration parameter</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<synopsis>
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ALTER SYSTEM SET <replaceable class="parameter">configuration_parameter</replaceable> { TO | = } { <replaceable class="parameter">value</replaceable> | '<replaceable class="parameter">value</replaceable>' | DEFAULT }
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ALTER SYSTEM RESET <replaceable class="parameter">configuration_parameter</replaceable>
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ALTER SYSTEM 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>ALTER SYSTEM</command> is used for changing server configuration
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parameters across the entire database cluster. It can be more convenient
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than the traditional method of manually editing
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the <filename>postgresql.conf</filename> file.
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<command>ALTER SYSTEM</command> writes the given parameter setting to
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the <filename>postgresql.auto.conf</filename> file, which is read in
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addition to <filename>postgresql.conf</filename>.
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Setting a parameter to <literal>DEFAULT</literal>, or using the
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<command>RESET</command> variant, removes that configuration entry from the
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<filename>postgresql.auto.conf</filename> file. Use <literal>RESET
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ALL</literal> to remove all such configuration entries.
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</para>
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<para>
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Values set with <command>ALTER SYSTEM</command> will be effective after
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the next server configuration reload, or after the next server restart
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in the case of parameters that can only be changed at server start.
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A server configuration reload can be commanded by calling the SQL
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function <function>pg_reload_conf()</function>, running <literal>pg_ctl reload</literal>,
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or sending a <systemitem>SIGHUP</systemitem> signal to the main server process.
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</para>
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<para>
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Only superusers can use <command>ALTER SYSTEM</command>. Also, since
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this command acts directly on the file system and cannot be rolled back,
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it is not allowed inside a transaction block or function.
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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 configuration parameter. Available parameters are
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documented in <xref linkend="runtime-config"/>.
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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><replaceable class="parameter">value</replaceable></term>
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<listitem>
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<para>
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New value of the parameter. Values can be specified as string
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constants, identifiers, numbers, or comma-separated lists of
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these, as appropriate for the particular parameter.
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<literal>DEFAULT</literal> can be written to specify removing the
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parameter and its value from <filename>postgresql.auto.conf</filename>.
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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>Notes</title>
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<para>
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This command can't be used to set <xref linkend="guc-data-directory"/>,
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nor parameters that are not allowed in <filename>postgresql.conf</filename>
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(e.g., <link linkend="runtime-config-preset">preset options</link>).
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</para>
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<para>
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See <xref linkend="config-setting"/> for other ways to set the parameters.
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</para>
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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 <literal>wal_level</literal>:
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<programlisting>
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ALTER SYSTEM SET wal_level = replica;
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</programlisting>
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</para>
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<para>
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Undo that, restoring whatever setting was effective
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in <filename>postgresql.conf</filename>:
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<programlisting>
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ALTER SYSTEM RESET wal_level;
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</programlisting></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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The <command>ALTER SYSTEM</command> statement is a
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<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"/></member>
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<member><xref linkend="sql-show"/></member>
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</simplelist>
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</refsect1>
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</refentry>
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