Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> Gregory Stark <stark(at)enterprisedb(dot)com> writes:
>> I think Postgres can't do better because there could be a NULL in the
>> subquery. If there's a NULL in the subquery then no record would match.
>
> Yeah. NOT IN does not have the right semantics to become an antijoin.
If we noticed that the columns in the subquery are all guaranteed to be not
null could we do it then?
--
Gregory Stark
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