From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | "Li, Zheng" <zhelli(at)amazon(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Richard Guo <riguo(at)pivotal(dot)io>, "Finnerty, Jim" <jfinnert(at)amazon(dot)com> |
Subject: | Re: NOT IN subquery optimization |
Date: | 2019-03-03 22:14:25 |
Message-ID: | CAKJS1f96PQq278QaNhoXSrYknCRkLwwJYapTqk-bmbuW2mX+Mg@mail.gmail.com |
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On Mon, 4 Mar 2019 at 11:06, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> writes:
> > On Mon, 4 Mar 2019 at 04:42, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> You absolutely will get errors during btree insertions and searches
> >> if a datatype's btree comparison functions ever return NULL (for
> >> non-NULL inputs).
>
> > I understand this is the case if an index happens to be used, but
> > there's no guarantee that's going to be the case. I was looking at the
> > case where an index was not used.
>
> Not following your point? An index opclass is surely not going to be
> designed on the assumption that it can never be used in an index.
> Therefore, its support functions can't return NULL unless the index AM
> allows that.
I agree that it makes sense that the behaviour of the two match. I was
trying to hint towards that when I said:
> If you're saying something doing that is
> fundamentally broken, then I guess we're okay.
but likely I didn't make that very clear.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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