CVSROOT: /cvsroot
Module name: pgsql-server
Changes by: tgl@postgresql.org 03/02/15 15:12:41
Modified files:
src/backend/optimizer/path: allpaths.c pathkeys.c
src/backend/optimizer/plan: planner.c
src/backend/optimizer/util: pathnode.c relnode.c tlist.c
src/include/optimizer: pathnode.h paths.h tlist.h
Log message:
Teach planner how to propagate pathkeys from sub-SELECTs in FROM up to
the outer query. (The implementation is a bit klugy, but it would take
nontrivial restructuring to make it nicer, which this is probably not
worth.) This avoids unnecessary sort steps in examples like
SELECT foo,count(*) FROM (SELECT ... ORDER BY foo,bar) sub GROUP BY foo
which means there is now a reasonable technique for controlling the
order of inputs to custom aggregates, even in the grouping case.
