Re: [HACKERS] GEQO optimizer (was Re: Backend message type 0x44 arrived while idle) - Mailing list pgsql-hackers

> I have observed that the regular optimizer requires about 50MB to plan
> some ten-way joins, and can exceed my system's 128MB process data limit
> on some eleven-way joins.  We currently have the GEQO threshold set at
> 11, which prevents the latter case by default --- but 50MB is a lot.
> I wonder whether we shouldn't back the GEQO threshold off to 10.
> (When I suggested setting it to 11, I was only looking at speed relative
> to GEQO, not memory usage.  There is now a *big* difference in memory
> usage...)  Comments?

You chose 11 by comparing GEQO with non-GEQO.  I think you will find
that with your improved GEQO, GEQO is faster for smaller number of
joins, preventing the memory problem.  Can you check the speeds again?

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