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List:       postgresql-general
Subject:    Re: Explain and filter over subplans
From:       Chantal Keller <chantal.keller () universite-paris-saclay ! fr>
Date:       2024-01-19 9:17:46
Message-ID: d3339be7-4e51-4119-8789-531583189a0a () universite-paris-saclay ! fr
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Thank you very much for your quick answer and patch!

I tested and this is exactly what I was looking for :-)

Best
Chantal




Le 18/01/2024 à 18:55, Tom Lane a écrit  :
> Chantal Keller <chantal.keller@universite-paris-saclay.fr> writes:
>> I would like "explain" to output formulas for filtering over
>> subplans. Is it possible?
> 
> No, and that's been a to-do item for a long time.
> 
> Currently, EXPLAIN just ignores the "testexpr" field of SubPlan
> nodes, which is what you are after.  We could print it, if we
> could figure out an intelligible representation.  In the example
> you give, the testexpr would probably render as "t.a >= $0"
> where $0 represents the subplan's output column.
> 
> A very rough sketch, perhaps, is that instead of just
> "(SubPlan 1)", we could print "(ALL t.a >= $0 FROM SubPlan 1)".
> Some of the other SubLinkTypes might be harder to represent
> in a way that makes sense to users.
> 
> I made a quick-hack patch to play with, if you're interested.
> 
> 			regards, tom lane
> 


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