Re: Problems with hash join over nested loop - Mailing list pgsql-performance

From Tom Lane
Subject Re: Problems with hash join over nested loop
Date
Msg-id 7541.1383174399@sss.pgh.pa.us
Whole thread Raw
In response to Re: Problems with hash join over nested loop  (Jim Nasby <jnasby@enova.com>)
List pgsql-performance
Jim Nasby <jnasby@enova.com> writes:
> Oh, and in my 28 table case ru_minflt was 428 4k memory pages (1.7MB). Not a great measurement, but better than
nothing.I didn't detect anything noticeable on vmstat either, so I don't think the consumption is huge (an email in the
olderthread mentioned 1GB... I'm not seeing that). 

Note that what matters here is not so much the number of base relations as
the number of possible join paths, which varies quite a lot depending on
the given and deduced join conditions.  Worst-case is where join
conditions are available between any two base relations, which is not
a real common case.

            regards, tom lane


pgsql-performance by date:

Previous
From: Jim Nasby
Date:
Subject: Re: Problems with hash join over nested loop
Next
From: Ben Hoyt
Date:
Subject: Re: Re: Adding foreign key constraint holds exclusive lock for too long (on production database)