Re: NOT IN subquery optimization - Mailing list pgsql-hackers

From Tom Lane
Subject Re: NOT IN subquery optimization
Date
Msg-id 5699.1551650765@sss.pgh.pa.us
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In response to Re: NOT IN subquery optimization  (David Rowley <david.rowley@2ndquadrant.com>)
Responses Re: NOT IN subquery optimization
List pgsql-hackers
David Rowley <david.rowley@2ndquadrant.com> writes:
> On Mon, 4 Mar 2019 at 04:42, Tom Lane <tgl@sss.pgh.pa.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.

            regards, tom lane


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