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Re: Optimization idea

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Vlad Arkhipov <arhipov(at)dc(dot)baikal(dot)ru>
Cc: Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Optimization idea
Date: 2010-04-29 03:17:25
Message-ID: AANLkTikqfvY_tCJbxg_lE0ccqvxecKmowpId5_YF3zog@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Wed, Apr 28, 2010 at 5:37 AM, Vlad Arkhipov <arhipov(at)dc(dot)baikal(dot)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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