<listitem>

<para>

<literal>forced</literal> &mdash;

this mode tries to optimize all queries together, regardless of

this mode tries to optimize allnewqueries together, regardless of

the query type.

</para>

</listitem>

mode. However, since the <literal>forced</literal> mode lacks

intelligent tuning, performance may decrease for some queries.

If you see performance issues in this mode, switch <filename>aqo</filename> to the

<literal>controlled</literal> mode:

<literal>controlled</literal> mode.

</para>

<programlisting>

SET aqo.mode = 'controlled';

</programlisting>

<para>

In the <literal>controlled</literal> mode, <filename>aqo</filename> does not collect statistics for new

query types, so they will not be optimized. For known query

UPDATE aqo_queries SET use_aqo=false, learn_aqo=false, auto_tuning=false;

</programlisting>

</sect3>

<sect3 id="using-aqo-on-standby">

<title>Using aqo on Standby</title>

<para>

In master-standby configurations, <filename>aqo</filename>

statistics on standby is inherited from master in read-only mode.

Standby queries do not update <filename>aqo</filename> statistics,

regardless of the current <filename>aqo</filename> settings.

If you would like to update the statistics on

standby for one or more query types, you must run these queries

on master and synchronize the standby.

</para>

<para>

You can define whether to use <filename>aqo</filename> statistics

for standby queries independent of the master configuration,

toggling <filename>aqo</filename> modes as required. By default,

<filename>aqo</filename> optimizes queries on standby as follows:

<itemizedlist>

<listitem>

<para>

In <literal>intelligent</> and <literal>controlled</> modes,

<filename>aqo</filename> statistics is only used for the

alreadyknown query types.

</para>

</listitem>

<listitem>

<para>

In the <literal>forced</> mode,

<filename>aqo</filename> tries to optimize the unknown

queries based on the common statistics collected in the

<literal>forced</> mode on master, if any. If the common

statistics is not found, <filename>aqo</filename> falls back

to the default query planner. All the known query types continue using

the available statistics.

</para>

</listitem>

<listitem>

<para>

The <literal>disabled</literal> mode switches off the collected

statistics completely, relying on the default query planner

for all queries.

</para>

</listitem>

</itemizedlist>

</para>

<para>

If you fine-tuned optimization settings for specific query types

on master, these settings override the default <filename>aqo</filename>

behavior, unless you choose the <literal>disabled</literal> mode.

For details, see <xref linkend="aqo-advanced-query-tuning">.

</para>

</sect3>

</sect2>

<sect2 id="aqo-reference">

<title>Reference</title>