On 1 November 2018 at 12:11, Tomas Vondra <tomas.von...@2ndquadrant.com> wrote: > I still have trouble imagining what exactly would the function do to > determine if the optimization can be applied to substr() and similar > collation-dependent cases.
I guess the function would have to check for a Const offset of 0, and a collection, perhaps of "C" for the 1st arg. In any case, I wouldn't want this idea to be hung up on the fact we can't determine how to make substr() work correctly with it. I'm most interested in date_trunc() and friends. A first cut implementation would not have to implement functions for everything that's possible to implement. -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
