Marti Raudsepp <ma...@juffo.org> writes:
> This patch enables a simple optimization in
> eval_const_expressions_mutator. If we know that one argument to
> DistinctExpr is NULL then we can optimize it to a NullTest, which can
> be an indexable expression.
Uh ... how much do we care about that? I can't say that I've heard many
people complain about the fact that IS [NOT] DISTINCT FROM is poorly
optimized -- which it is, in general, and this patch chips away at that
only a tiny bit, not enough to make it recommendable. If we really
wanted to make that a first-class operation we would need far more work
than this. Plus I don't see why anyone would write the specific case
"IS [NOT] DISTINCT FROM NULL" when they could write half as much.
regards, tom lane
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