On Mon, Nov 25, 2024 at 3:55 PM Robert Haas <robertmh...@gmail.com> wrote: > There are cases where we don't already draw the necessary conclusions, > such as a>1 and a>2, which could be simplified to a>2. But those cases > aren't necessarily that common.
Actually, we do use the more restrictive operator with cases like "a>1 and a>2" -- but only in contexts that happen to involve a B-Tree index scan, where _bt_preprocess_keys gets called. So it's a bit hit or miss. Tom has in the past expressed an interesting in moving the stuff in _bt_preprocess_keys into the planner: https://www.postgresql.org/message-id/2587523.1647982...@sss.pgh.pa.us Note that almost nothing in _bt_preprocess_keys is particularly related to nbtree itself, except perhaps for the stuff that marks scan keys required. The fact that "WHERE a IN (1, 2, 3) AND a < 2" can actually be simplified to "WHERE a = 1" has exactly nothing to do with B-Tree index scans, but we'll only do this simplification in the context of a B-Tree index scan. There is also some redundancy between _bt_preprocess_keys and the planner, which is less than ideal. -- Peter Geoghegan
