From: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> |
---|---|
To: | Artur Zając <azajac(at)ang(dot)com(dot)pl>, pgsql-performance(at)lists(dot)postgresql(dot)org |
Subject: | Re: IS NOT DISTINCT FROM statement |
Date: | 2019-03-08 11:45:39 |
Message-ID: | 9d4c7b0de250db9aef716600ca6e39652738ff4e.camel@cybertec.at |
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Lists: | pgsql-performance |
Artur Zając wrote:
> Is there any reason that „NOT DISTINCT FROM” can’t be autotransformed to „=” when value
> on right side of expression is not NULL or is this any way to use index with „IS NOT DISTINCT FROM” statement?
That would subtly change the semantics of the expression:
test=> SELECT NULL IS NOT DISTINCT FROM 21580;
?column?
----------
f
(1 row)
test=> SELECT NULL = 21580;
?column?
----------
(1 row)
One expression is FALSE, the other NULL.
It doesn't matter in the context of your specific query, but it could matter.
Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com
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