From: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
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To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Allowing NOT IN to use ANTI joins |
Date: | 2014-06-09 10:01:54 |
Message-ID: | 20140609100154.GA7044@svana.org |
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Lists: | pgsql-hackers |
On Mon, Jun 09, 2014 at 12:36:30AM +1200, David Rowley wrote:
> Currently pull_up_sublinks_qual_recurse only changes the plan for NOT
> EXISTS queries and leaves NOT IN alone. The reason for this is because the
> values returned by a subquery in the IN clause could have NULLs.
Awesome. I've had a brief look at the patch and other than a line of
extraneous whitespace it looks sane.
Since it is only testing on NOT IN queries I don't think there are any
issues with it slowing down simple queries.
I also note you can't prove "id+1" not null. At first I thought you
might be able to prove this not null if the operator/function was
strict, but then I realised that strict only means "null if input is
null" not "output is only null if inputs are null". Pity.
Nice work.
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> He who writes carelessly confesses thereby at the very outset that he does
> not attach much importance to his own thoughts.
-- Arthur Schopenhauer
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