Re: Selectivity of "=" (Re: [HACKERS] Index not used on simple se lect)

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От Tom Lane
Тема Re: Selectivity of "=" (Re: [HACKERS] Index not used on simple se lect)
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Msg-id 9731.933171407@sss.pgh.pa.us
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Ответ на Re: Selectivity of "=" (Re: [HACKERS] Index not used on simple se lect)  (Zeugswetter Andreas IZ5 <Andreas.Zeugswetter@telecom.at>)
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Zeugswetter Andreas IZ5 <Andreas.Zeugswetter@telecom.at> writes:
>> Yes, I think we index nulls.  What are partial indexes?
>> 
> A create index statement that accepts a where condition. All
> rows that satisfy the where condition are indexed, others not.
> This needs intelligence in the optimizer.

> This was in postgresql code some time ago, but was removed
> for some reason I don't remember.

It was?  There's still a ton of code in the optimizer to support it
(a big chunk of indxqual.c is for testing index predicates).
        regards, tom lane


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