Re: from_collapse_limit vs. geqo_threshold

Robert Haas <robertmhaas@gmail.com> writes:
> On Mon, Jun 1, 2009 at 3:34 PM, Selena Deckelmann <selena@endpoint.com> wrote:
>> Suggested revision of Robert's prose:
>> 
>> Because genetic query optimization may be triggered, increasing
>> from_collapse_limit should be considered relative to <xref
>> linkend="guc-geqo-threshold">.

> Here's my attempt.

I applied the attached, along with some other wordsmithing.
        regards, tom lane

***************
*** 2252,2261 ****         The planner will merge sub-queries into upper queries if the         resulting
<literal>FROM</literal>list would have no more than         this many items.  Smaller values reduce planning time but
might
!         yield inferior query plans.  The default is eight.  It is usually
!         wise to keep this less than <xref linkend="guc-geqo-threshold">.         For more information see <xref
linkend="explicit-joins">.       </para>       </listitem>      </varlistentry> 
 
--- 2261,2275 ----         The planner will merge sub-queries into upper queries if the         resulting
<literal>FROM</literal>list would have no more than         this many items.  Smaller values reduce planning time but
might
!         yield inferior query plans.  The default is eight.         For more information see <xref
linkend="explicit-joins">.       </para>
 
+ 
+        <para>
+         Setting this value to <xref linkend="guc-geqo-threshold"> or more
+         may trigger use of the GEQO planner, resulting in nondeterministic
+         plans.  See <xref linkend="runtime-config-query-geqo">.
+        </para>       </listitem>      </varlistentry>