Tom Lane wrote:
Only two of them are logically equivalent. Consider NULL.
Ohhh IS NOT TRUE or IS NOT FALSE also match NULL, I never knew this :)
> I'm not totally comfortable with the idea.Even for the first two, assuming equivalence requires hard-wiring an assumption about the behavior of the "bool = bool" operator; which is a user-redefinable operator.
Ok, I see your point and the problems that may arise, but I hope wou will agree with me that from the point of view of the user, both clauses have the same meaning and the index usage should be consistant with it.
Unfortunatelly I don't know very well PostgreSQL internals, so I may be saying a load of bullshits, but wouldn't be possible to consider any evaluation of a bool expression in the form of bool=bool with true as the second 'bool'[1] ? At least as a TODO item ?
Thanks!
Bye!
[1] Eventually including the "var IS TRUE" and "var IS FALSE" (not var IS NOT ...) which already are special syntax cases if I am not wrong.
--
Daniele Orlandi
Planet Srl
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