With the just-committed changes in PathKey representation, the core
backend is now pretty well invested in the assumption that index AMs
that can deliver sorted results will use btree-compatible strategy
numbers for their order-related operators. This doesn't seem to me
to be any huge limitation (a new AM might possibly define additional
operator strategies, but that needn't stop it from using 1-5 with
the same meanings as btree). So I'm thinking that the pg_am columns
amorderstrategy and amdescorder are redundant and should be replaced
with a simple boolean, "amcansort" perhaps. Any objections?
regards, tom lane
