Re: Optimizer & boolean syntax

On Thu, 21 Nov 2002, Christopher Kings-Lynne wrote:

> > > I think his point is that they _should_ be equivalent. Surely there's
> > > something in the optimiser that discards '=true' stuff, like 'a=a'
> should be
> > > discarded?
> >
> > I figure that's what he meant, but it isn't what was said. ;)
> >
> > "col" isn't of the general form "indexkey op constant" or "constant op
> > indexkey" which I presume it's looking for given the comments in
> > indxpath.c. I'm not sure what the best way to make it work would be given
> > that presumably we'd want to make col IS TRUE/FALSE use an index at the
> > same time (since that appears to not do so as well).
>
> Not that I see the point of indexing booleans, but hey :)

While full indexes do seem futile, partial indexes can be quite useful.

select articles from forum where approved is false

if 99.9% of all articles are approved would be quite common.