Re: Optimization idea - Mailing list pgsql-performance

From Robert Haas
Subject Re: Optimization idea
Date
Msg-id AANLkTikqfvY_tCJbxg_lE0ccqvxecKmowpId5_YF3zog@mail.gmail.com
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In response to Optimization idea  (Vlad Arkhipov <arhipov@dc.baikal.ru>)
Responses Re: Optimization idea
List pgsql-performance
On Wed, Apr 28, 2010 at 5:37 AM, Vlad Arkhipov <arhipov@dc.baikal.ru> wrote:
> Even if it will be done it does not solve the original issue. If I
> understood you right there is now no any decent way of speeding up the query
>
> select *
> from t2
> join t1 on t1.t = t2.t
> where t1.id = X;
>
> except of the propagating the t1.id value to the table t2 and createing and
> index for this column?

No, what I'm saying is that if X is any ANY() expression, you can get
a faster plan in this case by writing:

SELECT * FROM t2 JOIN t1 ON t1.t = t2.t WHERE t2.id = X;

For me this is about 8x faster.

...Robert

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