Re: [HACKERS] GEQO optimizer (was Re: Backend message type 0x44 arrived while idle)

> 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?

--
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026