Re: Understanding how partial indexes work?

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От Tom Lane
Тема Re: Understanding how partial indexes work?
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Msg-id 4971.1196987547@sss.pgh.pa.us
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Ответ на Re: Understanding how partial indexes work?  ("Chris Velevitch" <chris.velevitch@gmail.com>)
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"Chris Velevitch" <chris.velevitch@gmail.com> writes:
> On Dec 7, 2007 2:39 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Is it worth the trouble?  You didn't mention the statistics involved,
>> but ordinarily I'd think a non-equal condition is too nonselective
>> to justify the cost of maintaining an extra index.

> Yes, I did neglect to mention the stats. Y is the status of the record
> which represents the life cycle of the record starting at zero and
> ending up at k3. So basically the query would retrieving and the
> partial index will indexing records which aren't at their end of life.
> So the number of records where Y <> k3 will be low and the number of
> records where Y = k3 will be growing over time.

OK, in that case the partial index might be worth trying.

            regards, tom lane

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