Re: Question about indexes

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От
Greg Stark
Тема
Re: Question about indexes
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87vfmwrtxt.fsf@stark.xeocode.com
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Дерево обсуждения
Question about indexes Greg Stark <gsstark@mit.edu>
Re: Question about indexes Tom Lane <tgl@sss.pgh.pa.us>
Re: Question about indexes Greg Stark <gsstark@mit.edu>
Re: Question about indexes Tom Lane <tgl@sss.pgh.pa.us>
Re: Question about indexes Greg Stark <gsstark@mit.edu>
Re: Question about indexes Tom Lane <tgl@sss.pgh.pa.us>
Re: Question about indexes Greg Stark <gsstark@mit.edu>
Re: Question about indexes Tom Lane <tgl@sss.pgh.pa.us>
Re: Question about indexes "Simon Riggs" <simon@2ndquadrant.com>
Re: Question about indexes Greg Stark <gsstark@mit.edu>
Re: Question about indexes Bruce Momjian <pgman@candle.pha.pa.us>
Re: Question about indexes Eric Ridge <ebr@tcdi.com>
Re: Question about indexes Tom Lane <tgl@sss.pgh.pa.us>
Re: Question about indexes Hannu Krosing <hannu@tm.ee>
Re: Question about indexes Tom Lane <tgl@sss.pgh.pa.us>
Re: Question about indexes Hannu Krosing <hannu@tm.ee>
Re: Question about indexes Greg Stark <gsstark@mit.edu>
Re: Question about indexes Tom Lane <tgl@sss.pgh.pa.us>
Re: Question about indexes Bruce Momjian <pgman@candle.pha.pa.us>
Re: Question about indexes Alvaro Herrera <alvherre@dcc.uchile.cl>
Re: Question about indexes Bruce Momjian <pgman@candle.pha.pa.us>
Re: Question about indexes Tom Lane <tgl@sss.pgh.pa.us>
Re: Question about indexes Bruce Momjian <pgman@candle.pha.pa.us>

Tom Lane  writes:

> In any case, this discussion is predicated on the assumption that the
> operations involving the bitmap are a significant fraction of the total
> time, which I think is quite uncertain.  Until we build it and profile
> it, we won't know that.

The other thought I had was that it would be difficult to tell when to follow
this path. Since the main case where it wins is when the individual indexes
aren't very selective but the combination is very selective, and we don't have
inter-column correlation statistics ...

-- 
greg


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