Re: Equivalence Classes when using IN

From: David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>
To: Kim Rose Carlsen <krc(at)hiper(dot)dk>
Cc: "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org>
Subject: Re: Equivalence Classes when using IN
Date: 2017-10-08 20:49:27
Message-ID: CAKJS1f8RHOi-=KjCj51bU+CPpeJyaeYyDQbFL08qaQBEj4U9Gg@mail.gmail.com
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On 9 October 2017 at 08:01, Kim Rose Carlsen <krc(at)hiper(dot)dk> wrote:
> Is this because postgres never consider IN clause when building equivalence
> class's?

Only btree equality operators are considered at the moment.

> Are there any interests in adding such rule?

There's been some discussion on it previously, although there is lots
to still be worked out, for example, it's not that clear if it will
always be a win to always apply the qual.

There are more details of the discussion in [1], although there's
probably lots more threads to be found if you search the archives.

[1] https://www.postgresql.org/message-id/flat/CAKJS1f9FK_X_5HKcPcSeimy16Owe3EmPmmGsGWLcKkj_rW9s6A%40mail(dot)gmail(dot)com#CAKJS1f9FK_X_5HKcPcSeimy16Owe3EmPmmGsGWLcKkj_rW9s6A(at)mail(dot)gmail(dot)com

--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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