From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | "Clinton James" <cjames(at)callone(dot)net> |
Cc: | pgsql-general(at)postgreSQL(dot)org |
Subject: | Re: Another "why am I not using the indicies?" |
Date: | 2001-05-04 15:18:16 |
Message-ID: | 25228.988989496@sss.pgh.pa.us |
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Lists: | pgsql-general |
"Clinton James" <cjames(at)callone(dot)net> writes:
> True, using a different cust_num, it is possible there may be a couple of
> cust_num where that would be true. The majority will not have even near
> that many. In this case there are only 13 matching records. Is VACUUMDB
> ANALYZE using the worst case (the cust_num with the greatest number of rows)
> senario for this?
Yes, because that's as far as the statistics go at the moment :-(.
The frequency of the most common value is basically all the info the
planner has about the data distribution, and so a highly skewed
distribution leads to bad plan choices.
I am presently working on better statistics ... to appear in 7.2 ...
regards, tom lane
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