Re: Planner not using UNIQUEness of index properly

John Burger <john@mitre.org> writes:
> create unique index ix_allWords_lower on allWords (lower(word));

> To my surprise, the planner does not seem to realize that only one
> row can result from using this index:

> I would think UNIQUE => one row is pretty obvious - what am I
> missing?  (Unless it's that I'm still stuck in 7.4.)

That would be the problem :-( ... a look at the code suggests that the
ability to do anything intelligent with expression indexes was added
in 8.0.

            regards, tom lane