On Mon, Jun 1, 2009 at 3:34 PM, Selena Deckelmann <sel...@endpoint.com> 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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