Re: not using partial index

Willy-Bas Loos <willybas@gmail.com> writes:
> [ NOT field1 ISNULL is not seen as equivalent to field1 IS NOT NULL ]

> Any ideas why this might be?

The planner does not spend an infinite number of cycles on trying to
make different expressions look alike.

As it happens, 9.1 does know this equivalence, as a byproduct of
http://git.postgresql.org/gitweb?p=postgresql.git&a=commitdiff&h=220e45bf325b061b8dbd7451f87cedc07da61706
But I don't consider it a bug that older versions don't do it.

            regards, tom lane