nocfbot-0006-Clarify-ST_NONE-intent.txt

From e267e4f1e40bd6919efb4ebef769e60da3a7ac4e Mon Sep 17 00:00:00 2001
From: Henson Choi <assam258@gmail.com>
Date: Fri, 20 Mar 2026 16:59:21 +0900
Subject: [PATCH] Clarify ST_NONE intent in RPSkipTo enum and WindowClause
 initialization

ST_NONE serves as the sentinel value (0) indicating that a WindowClause
has no RPR AFTER MATCH clause. This was implicit via palloc0 zero-filling
but not documented.

Add a comment to the ST_NONE enum value explaining its role as the default
for non-RPR windows, and add an explicit assignment in
transformWindowDefinitions() to make the intent clear in code.
---
 src/backend/parser/parse_clause.c | 2 ++
 src/include/nodes/parsenodes.h    | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index b30c22933ec..3796a69ac3a 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -2889,6 +2889,8 @@ transformWindowDefinitions(ParseState *pstate,
 		 * And prepare the new WindowClause.
 		 */
 		wc = makeNode(WindowClause);
+		wc->rpSkipTo = ST_NONE; /* ST_NONE marks this as a non-RPR window;
+								 * overridden by transformRPR() if RPR is used */
 		wc->name = windef->name;
 		wc->refname = windef->refname;
 
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 432b0573990..c5bf2ce80bf 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -583,7 +583,8 @@ typedef struct SortBy
  */
 typedef enum RPSkipTo
 {
-	ST_NONE,					/* AFTER MATCH omitted */
+	ST_NONE,					/* no AFTER MATCH clause; default for non-RPR
+								 * windows */
 	ST_NEXT_ROW,				/* SKIP TO NEXT ROW */
 	ST_PAST_LAST_ROW,			/* SKIP TO PAST LAST ROW */
 } RPSkipTo;
-- 
2.50.1 (Apple Git-155)