From: Tom Lane <tgl@sss.pgh.pa.us>
To: Davor J. <DavorJ@live.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: queries with subquery constraints on partitioned tables not optimized?
Date: Tue, 02 Feb 2010 19:14:14 -0500
Message-ID: <5002.1265156054@sss.pgh.pa.us> (raw)
In-Reply-To: <hk8sd1$2b79$1@news.hub.org>
References: <hk8sd1$2b79$1@news.hub.org>
"Davor J." <DavorJ@live.com> writes:
> Now, if one takes a subquery for "1", the optimizer evaluates it first
> (let's say to "1"), but then searches for it (sequentially) in every
> partition, which, for large partitions, can be very time-consuming and goes
> beyond the point of partitioning.
No, the optimizer doesn't "evaluate it first". Subqueries aren't ever
assumed to reduce to constants. (If you actually do have a constant
expression, why don't you just leave out the word SELECT?)
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, DavorJ@live.com
Subject: Re: queries with subquery constraints on partitioned tables not optimized?
In-Reply-To: <5002.1265156054@sss.pgh.pa.us>
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