Re: Horribly slow hash join - Mailing list pgsql-performance

From Tom Lane
Subject Re: Horribly slow hash join
Date
Msg-id 450.1082133251@sss.pgh.pa.us
Whole thread Raw
In response to Horribly slow hash join  ("Jim C. Nasby" <jim@nasby.net>)
Responses Re: Horribly slow hash join
List pgsql-performance
"Jim C. Nasby" <jim@nasby.net> writes:
> Note the time for the hash join step:

Have you ANALYZEd these tables lately?

It looks to me like it's hashing on some column that has only a small
number of distinct values, so that the hash doesn't actually help to
avoid comparisons.  The planner should know better than to choose such
a plan, but if it's working with obsolete stats ...

            regards, tom lane

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