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Re: queries with subquery constraints on partitioned tables not optimized? - Mailing list pgsql-performance

From Tom Lane
Subject Re: queries with subquery constraints on partitioned tables not optimized?
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In response to queries with subquery constraints on partitioned tables not optimized?  ("Davor J." <[email protected]>)
Responses Re: queries with subquery constraints on partitioned tables not optimized?
Re: queries with subquery constraints on partitioned tables not optimized?
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"Davor J." <[email protected]> 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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