<term><varname>enable_hashjoin</varname> (<type>boolean</type>)
      <indexterm>
       <primary><varname>enable_hashjoin</varname> configuration parameter</primary>
      </indexterm>
      </term>
      <listitem>
       <para>
        Enables or disables the query planner's use of hash-join plan
        types. The default is <literal>on</literal>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="guc-enable-incremental-sort" xreflabel="enable_incremental_sort">
      <term><varname>enable_incremental_sort</varname> (<type>boolean</type>)
      <indexterm>
       <primary><varname>enable_incremental_sort</varname> configuration parameter</primary>
      </indexterm>
      </term>
      <listitem>
       <para>
        Enables or disables the query planner's use of incremental sort steps.
        The default is <literal>on</literal>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="guc-enable-indexscan" xreflabel="enable_indexscan">
      <term><varname>enable_indexscan</varname> (<type>boolean</type>)
      <indexterm>
       <primary>index scan</primary>
      </indexterm>
      <indexterm>
       <primary><varname>enable_indexscan</varname> configuration parameter</primary>
      </indexterm>
      </term>
      <listitem>
       <para>
        Enables or disables the query planner's use of index-scan and
        index-only-scan plan types.  The default is <literal>on</literal>.
        Also see <xref linkend="guc-enable-indexonlyscan"/>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="guc-enable-indexonlyscan" xreflabel="enable_indexonlyscan">
      <term><varname>enable_indexonlyscan</varname> (<type>boolean</type>)
      <indexterm>
       <primary><varname>enable_indexonlyscan</varname> configuration parameter</primary>
      </indexterm>
      </term>
      <listitem>
       <para>
        Enables or disables the query planner's use of index-only-scan plan
        types (see <xref linkend="indexes-index-only-scans"/>).
        The default is <literal>on</literal>.  The
        <xref linkend="guc-enable-indexscan"/> setting must also be
        enabled to have the query planner consider index-only-scans.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="guc-enable-material" xreflabel="enable_material">
      <term><varname>enable_material</varname> (<type>boolean</type>)
      <indexterm>
       <primary><varname>enable_material</varname> configuration parameter</primary>
      </indexterm>
      </term>
      <listitem>
       <para>
        Enables or disables the query planner's use of materialization.
        It is impossible to suppress materialization entirely,
        but turning this variable off prevents the planner from inserting
        materialize nodes except in cases where it is required for correctness.
        The default is <literal>on</literal>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="guc-enable-memoize" xreflabel="enable_memoize">
      <term><varname>enable_memoize</varname> (<type>boolean</type>)
      <indexterm>
       <primary><varname>enable_memoize</varname> configuration parameter</primary>
      </indexterm>
      </term>
      <listitem>
       <para>
        Enables or disables the query planner's use of memoize plans for
        caching results from parameterized scans inside nested-loop joins.
        This plan type allows scans to the underlying plans to be skipped when
        the results for the current parameters are already in the cache.  Less
        commonly looked up results may be evicted from the cache when more
        space is required for new entries. The default is
        <literal>on</literal>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="guc-enable-mergejoin" xreflabel="enable_mergejoin">
      <term><varname>enable_mergejoin</varname> (<type>boolean</type>)
      <indexterm>
       <primary><varname>enable_mergejoin</varname>