Re: queries with subquery constraints on partitioned tables not optimized?

From: Tom Lane
Subject: Re: queries with subquery constraints on partitioned tables not optimized?
Date: ,
Msg-id: 5002.1265156054@sss.pgh.pa.us
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In response to: queries with subquery constraints on partitioned tables not optimized?  ("Davor J.")
Responses: Re: queries with subquery constraints on partitioned tables not optimized?  (Dimitri Fontaine)
Re: queries with subquery constraints on partitioned tables not optimized?  (Nikolas Everett)
List: pgsql-performance


"Davor J." <> 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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