Re: Transforming IN (...) to ORs, volatility

Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> I'd like us to still fix this so that there's no multiple evaluation -
> that would actually make BETWEEN more useful than it is today. I'm
> working on a patch to handle both BETWEEN and IN.

One other issue here is that the parser has traditionally handled
BETWEEN by multiply linking the same expression tree. I've wanted to
get rid of that behavior for a long time, but never got round to it.
It causes a lot of headaches for later processing, because you have to
be wary of multiply processing the same tree. If we switch BETWEEN
to something with a dedicated representation we could probably get rid
of all multiple-linking in the parser's output, allowing ensuing
simplifications downstream.

regards, tom lane