Re: [HACKERS] nested loops in joins, ambiguous rewrite rules

> >We turn on geqo at 8 relations. Try: > > SET GEQO TO 4 >
> >and try the query again. Let us know.
>
> Well isn't that something! Thanks so much for your help!
>
> I set the GEQO variable to 4 and now the 11.5 minute query
> executes in 6 seconds with this query plan:
>
> Hash Join (cost=21.99 size=152 width=124)
width=16)
>
>
> Are there any recommendations about what value *ought* to be
> set for GEQO? It seems to me like 'ON=8' is pretty high -- for
> us, it meant that UNLESS we explicity set that variable for
> every JOIN query of 6-7 tables, the joins were going to bog down
> to a total crawl, while sending memory and CPU consumption
> through the roof (roughly 22MB and 90-95%, respectively, for
> the entire query-processing period).

We have toyed with lowering it to 6. I think someone said that was too
low, but obviously, some queries need a value of 6 or lower. I don't
understand when that is the case, though. Any comments from anyone?

I believe the GEQO README was moved into the documentation in docs. It
used to be there, but is no longer.

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