От: Tom Lane
Тема: Re: slow index lookup
Дата: ,
Msg-id: 11812.1277258513@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: slow index lookup  (Alvaro Herrera)
Ответы: Re: slow index lookup  (Anj Adu)
Re: slow index lookup  (Anj Adu)
Список: pgsql-performance

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slow index lookup  (Anj Adu, )
 Re: slow index lookup  (Alvaro Herrera, )
  Re: slow index lookup  (Anj Adu, )
   Re: slow index lookup  ("Joshua D. Drake", )
    Re: slow index lookup  (Anj Adu, )
   Re: slow index lookup  ("Joshua D. Drake", )
  Re: slow index lookup  (Tom Lane, )
   Re: slow index lookup  (Anj Adu, )
   Re: slow index lookup  (Anj Adu, )
    Re: slow index lookup  ("Kevin Grittner", )

Alvaro Herrera <> writes:
> Excerpts from Anj Adu's message of mar jun 22 17:44:39 -0400 2010:
>> This query seems unreasonable slow on a well-indexed table (13 million
>> rows). Separate indexes are present on guardid_id , from_num and
>> targetprt columns.

> Maybe you need to vacuum or reindex?

Rethinking the set of indexes is probably a more appropriate suggestion.
Separate indexes aren't usefully combinable for a case like this --- in
principle the thing could do a BitmapAnd, but the startup time would be
pretty horrid, and the LIMIT 1 is discouraging it from trying that.
If this is an important case to optimize then you need a 3-column index.

            regards, tom lane


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