| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Gregory Stark <stark(at)enterprisedb(dot)com> |
| Cc: | "Jeff Davis" <pgsql(at)j-davis(dot)com>, len(at)pdx(dot)edu, len(at)cs(dot)pdx(dot)edu, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Understanding histograms |
| Date: | 2008-05-01 04:41:07 |
| Message-ID: | 561.1209616867@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
Gregory Stark <stark(at)enterprisedb(dot)com> writes:
> This is something that needs some serious thought though. In the case of
> partitioned tables I've seen someone get badly messed up plans because they
> had a couple hundred partitions each of which estimated to return 1 row. In
> fact of course they all returned 0 rows except the correct partition. (This
> was in a join so no constraint exclusion)
Yeah, one of the things we need to have a "serious" partitioning
solution is to get the planner's estimation code to understand
what's happening there.
regards, tom lane
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