server command
        line.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="guc-max-parallel-apply-workers-per-subscription" xreflabel="max_parallel_apply_workers_per_subscription">
      <term><varname>max_parallel_apply_workers_per_subscription</varname> (<type>integer</type>)
      <indexterm>
       <primary><varname>max_parallel_apply_workers_per_subscription</varname> configuration parameter</primary>
      </indexterm>
      </term>
      <listitem>
       <para>
        Maximum number of parallel apply workers per subscription. This
        parameter controls the amount of parallelism for streaming of
        in-progress transactions with subscription parameter
        <literal>streaming = parallel</literal>.
       </para>
       <para>
        The parallel apply workers are taken from the pool defined by
        <varname>max_logical_replication_workers</varname>.
       </para>
       <para>
        The default value is 2. This parameter can only be set in the
        <filename>postgresql.conf</filename> file or on the server command
        line.
       </para>
      </listitem>
     </varlistentry>

     </variablelist>
    </sect2>

   </sect1>

   <sect1 id="runtime-config-query">
    <title>Query Planning</title>

    <sect2 id="runtime-config-query-enable">
     <title>Planner Method Configuration</title>

      <para>
       These configuration parameters provide a crude method of
       influencing the query plans chosen by the query optimizer. If
       the default plan chosen by the optimizer for a particular query
       is not optimal, a <emphasis>temporary</emphasis> solution is to use one
       of these configuration parameters to force the optimizer to
       choose a different plan.
       Better ways to improve the quality of the
       plans chosen by the optimizer include adjusting the planner cost
       constants (see <xref linkend="runtime-config-query-constants"/>),
       running <link linkend="sql-analyze"><command>ANALYZE</command></link> manually, increasing
       the value of the <xref
       linkend="guc-default-statistics-target"/> configuration parameter,
       and increasing the amount of statistics collected for
       specific columns using <command>ALTER TABLE SET
       STATISTICS</command>.
      </para>

     <variablelist>
     <varlistentry id="guc-enable-async-append" xreflabel="enable_async_append">
      <term><varname>enable_async_append</varname> (<type>boolean</type>)
      <indexterm>
       <primary><varname>enable_async_append</varname> configuration parameter</primary>
      </indexterm>
      </term>
      <listitem>
       <para>
        Enables or disables the query planner's use of async-aware
        append plan types. The default is <literal>on</literal>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="guc-enable-bitmapscan" xreflabel="enable_bitmapscan">
      <term><varname>enable_bitmapscan</varname> (<type>boolean</type>)
      <indexterm>
       <primary>bitmap scan</primary>
      </indexterm>
      <indexterm>
       <primary><varname>enable_bitmapscan</varname> configuration parameter</primary>
      </indexterm>
      </term>
      <listitem>
       <para>
        Enables or disables the query planner's use of bitmap-scan plan
        types. The default is <literal>on</literal>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="guc-enable-distinct-reordering" xreflabel="enable_distinct_reordering">
      <term><varname>enable_distinct_reordering</varname> (<type>boolean</type>)
      <indexterm>
       <primary><varname>enable_distinct_reordering</varname> configuration parameter</primary>
      </indexterm>
      </term>
      <listitem>
       <para>
        Enables or disables the query planner's ability to reorder DISTINCT
        keys to match the input path's pathkeys. The default is <literal>on</literal>.
       </para>
      </listitem>
     </varlistentry>