nocfbot-0005-Fix-mark-handling-last_value-RPR.txt

From 31e7dacb8b0fa6ead63ff92c19aa5dfb0cde76a1 Mon Sep 17 00:00:00 2001
From: Henson Choi <assam258@gmail.com>
Date: Wed, 25 Mar 2026 00:37:50 +0900
Subject: [PATCH 05/40] Fix mark handling for last_value() under RPR

Enable mark advancement in window_last_value() for
better tuplestore memory usage in non-RPR cases, while
adding a guard in WinGetFuncArgInFrame to suppress it
for RPR SEEK_TAIL to prevent position invalidation
from reduced frame shifts.
---
 src/backend/executor/nodeWindowAgg.c | 10 ++++++++++
 src/backend/utils/adt/windowfuncs.c  |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 185d7a0d5ae..aed7cbef99a 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -4932,7 +4932,17 @@ WinGetSlotInFrame(WindowObject winobj, TupleTableSlot *slot,
 	if (isout)
 		*isout = false;
 	if (set_mark)
+	{
+		/*
+		 * If RPR is enabled and seek type is WINDOW_SEEK_TAIL, we set the
+		 * mark position unconditionally to frameheadpos. In this case the
+		 * frame always starts at CURRENT_ROW and never goes back, thus
+		 * setting the mark at the position is safe.
+		 */
+		if (winstate->rpPattern != NULL && seektype == WINDOW_SEEK_TAIL)
+			mark_pos = winstate->frameheadpos;
 		WinSetMarkPosition(winobj, mark_pos);
+	}
 	return 0;
 
 out_of_frame:
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index efb60c99052..74ef109f72e 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -682,7 +682,7 @@ window_last_value(PG_FUNCTION_ARGS)
 
 	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
-								  0, WINDOW_SEEK_TAIL, false,
+								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
 	if (isnull)
 		PG_RETURN_NULL();
-- 
2.50.1 (Apple Git-155)