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Re: [GENERAL] Simple Query not using Primary Key Index - Mailing list pgsql-general

From Vitaly Burovoy
Subject Re: [GENERAL] Simple Query not using Primary Key Index
Date
Msg-id CAKOSWNkhGqm6wWuAcrjjJYL0eKNQ6odFREXjgnki9bwA0Hb-6Q@mail.gmail.com
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In response to [GENERAL] Simple Query not using Primary Key Index  ("Podrigal, Aron" <aronp@guaranteedplus.com>)
Responses Re: [GENERAL] Simple Query not using Primary Key Index  (Aron Podrigal <aronp@guaranteedplus.com>)
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On 2/6/17, Podrigal, Aron <aronp@guaranteedplus.com> wrote:
> Hi,
>
> I noticed when I do a simple SELECT id FROM mytable WHERE id =
> 'cb81d070-4213-465f-b32e-b8db43b83a25'::UUID  Postgres does not use the
> primary key index and opts for a Seq Scan.
>
> I of course did VACUUM ANALYZE and I have reset statistics But no sign. Is
> there any particular thing I should be looking at?

Postgres uses specified access methods according to table's statistics.
If you have a small table, it is likely that Postgres uses SeqScan
because it is similar or cheaper than IndexScan. That's why it can
ignore existing indexes.

--
Best regards,
Vitaly Burovoy

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