Re: Row pattern recognition

Hi.

based on https://github.com/assam258-5892/postgres/tree/RPR-20260930
I have made some non-trivial refactoring in nodeWindowAgg.c, see attached.

The attached patch commit message is as follows:
================
Separate resolving the reduced frame from consuming it

ExecWindowAgg() resolves the reduced frame for every row it emits,
by calling
ensure_reduced_frame() before any window function or aggregate
runs; that is the
only place the match is driven. Everything after it should only
consumes the
recorded match through get_reduced_frame_status(), which reports how any row
position relates to it.

row_is_in_reduced_frame should be removed.

row_is_in_reduced_frame() blurred that division: it re-ran
ensure_reduced_frame() and then get_reduced_frame_status() again,
so consumers
looked as if they might resolve the match themselves.

While at it, I found the change to WinGetFuncArgInFrame() hard to
review: the
new WinGetSlotInFrame() mixes RPR logic into the existing frame
code. IGNORE
NULLS already it's own function: ignorenulls_getfuncarginframe().
Similarly we
can left WinGetFuncArgInFrame() unchanged (same as the master
branch) and moved the RPR logic into a
dedicated function, WinGetFuncArgInReducedFrame(). That
duplicates some code,
but the result is much cleaner, and I think the duplication is worth it.

================

--
jian
https://www.enterprisedb.com/