On Mon, Jun 1, 2009 at 3:34 PM, Selena Deckelmann <[email protected]> wrote:
> In the spirit of helping wrap-up 8.4 todo items...
> Robert Haas wrote:
>> For 8.4, I'd be happy to just improve the documentation. I think this
>> sentence could just be deleted from the section on
>> from_collapse_limit:
> My vote would be to provide some information.
>
> 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.
...Robert
*** a/doc/src/sgml/config.sgml
--- b/doc/src/sgml/config.sgml
***************
*** 2252,2259 **** SELECT * FROM parent WHERE key = 2400;
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>
--- 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. Note that if this
! value is less than <xref linkend="guc-geqo-threshold">, pulling up
! subqueries may trigger GEQO planning, since it will increase the
! number of <literal>FROM</literal> items.
For more information see <xref linkend="explicit-joins">.
</para>
</listitem>
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