Re: Postgres not willing to use an index?

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От Mario Splivalo
Тема Re: Postgres not willing to use an index?
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Msg-id 498FF72F.3000808@megafon.hr
обсуждение исходный текст
Ответ на Re: Postgres not willing to use an index?  (Tom Lane <tgl@sss.pgh.pa.us>)
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Tom Lane wrote:
>
> Hardly surprising --- a search on the index's lowest-order column would
> require scanning practically all of the index.  (If you think about the
> ordering of the index entries you'll see why.)  If this is a typical
> query then you need a separate index on transaction_time_commit.

Yes, actually I just moved transaction_time_commit column to the
begining of the index, since, most of the time I run queries based on
transaction_time_commit and then transaction_client_id and
transaction_destination_id.

> The fine manual goes into some detail about how to design indexes;
> http://www.postgresql.org/docs/8.3/static/indexes.html
> particularly 11.3, 11.5.

I see it now. I read the manual concerning CREATE INDEX command, and
there is no mention of multicolumn indices, did not notice Note that
points to Chapter 11.

    Mike


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