On Tue, 2003-09-30 at 09:54, Mike Mascari wrote:
> Arguile wrote:
>
> > On Tue, 2003-09-30 at 07:06, Mike Mascari wrote:
> >
> >>CREATE INDEX i_employees ON employees(lower(name));
> >>
> >>Let's also assume that the lower() function is computationally
> >>expensive. Now if I have a query like:
> >>
> >>SELECT lower(name)
> >>FROM employees
> >>WHERE lower(name) = 'mike'
> >>
> >>will PostgreSQL re-evaluate lower(name)? Is it necessary?
> >
> > No, it won't re-evaluate.
>
> I think it will.
You're correct, I misunderstood to which clause you were referring to: I
thought you were wondering about the lower(name) in the where clause.
Sorry for the confusion.
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
