Hi Andrew, On 25 Sep 2018, at 01:51, Andrew Gierth <and...@tao11.riddles.org.uk> wrote: > I haven't looked at the background of this, but if what you want to know > is whether the aggregate function has the semantics of min() or max() > (and if so, which) then the place to look is pg_aggregate.aggsortop.
Thanks for the pointer. I've had a quick look at pg_aggregate, and back at my code, but I think there is more to it than just the sorting property. Specifically we need to know about the aggregate function when combined with connectors <, <=, < ANY, <= ANY, < ALL and <= ALL (and their equivalents with ">" and ">="). Also, it looks like COUNT and SUM don't have a sortop (the other aggregates I've catered for do though). When I come to do the rework of the patch I'll take a more in-depth look though, and see if this can be utilised. > As for operators, you can only make assumptions about their meaning if > the operator is a member of some opfamily that assigns it some > semantics. I had clocked the BT semantics stuff when doing the PoC patch. I have used the "get_op_btree_interpretation" function for determining operator meaning. -Joe
