| From: | mlw <markw(at)mohawksoft(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Thomas Lockhart <thomas(at)fourpalms(dot)org>, Lincoln Yeoh <lyeoh(at)pop(dot)jaring(dot)my>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Louis-David Mitterrand <vindex(at)apartia(dot)org>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Index Scans become Seq Scans after VACUUM ANALYSE |
| Date: | 2002-04-17 17:49:16 |
| Message-ID: | 3CBDB59C.74A4C8D2@mohawksoft.com |
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| Lists: | pgsql-hackers |
Tom Lane wrote:
>
> mlw <markw(at)mohawksoft(dot)com> writes:
> > ... I have seen many instances of when
> > PostgreSQL refuses to use an index because the data distribution is uneven.
>
> This is fixed, or at least attacked, in 7.2. Again, I do not see this
> as an argument for making the planner stupider instead of smarter.
>
You completely ignored the point I was trying to make. Statistics are a
summation of the data, not the actual data. As such, it can not possibly
represent all possible configurations of tables.
Adding huristics, such as weighting for index scans, is not making the planner
stupider. It is making it smarter and more flexable.
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