nocfbot-0044-Tidy-up-row-pattern-recognition-pattern-compilati.txt

From 1e9d66e961bae1e3884be7c844c7faba252c4bed Mon Sep 17 00:00:00 2001
From: Henson Choi <assam258@gmail.com>
Date: Thu, 4 Jun 2026 20:28:51 +0900
Subject: [PATCH 44/68] Tidy up row pattern recognition pattern compilation

Mark the unreachable tails of the three node-type switches
(rprPatternEqual, optimizeRPRPattern, fillRPRPattern) with
pg_unreachable() instead of a "keep compiler quiet" return.
RPRPatternNodeType has only four members and each switch handles
all of them, so the trailing return can never be reached.

In buildRPRPattern(), the absorption-eligibility test guarded
against a ROWS frame redundantly: RPR is ROWS-only because
transformRPR() rejects RANGE and GROUPS up front, so the
FRAMEOPTION_ROWS term was always true.  Drop the hasLimitedFrame
variable, assert the ROWS-only invariant instead, and test
FRAMEOPTION_END_UNBOUNDED_FOLLOWING directly.

No behavior change.

Patch by Jian He, with minor adjustments.
---
 src/backend/optimizer/plan/rpr.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/backend/optimizer/plan/rpr.c b/src/backend/optimizer/plan/rpr.c
index 617a3869948..3205559c03a 100644
--- a/src/backend/optimizer/plan/rpr.c
+++ b/src/backend/optimizer/plan/rpr.c
@@ -132,7 +132,8 @@ rprPatternEqual(RPRPatternNode *a, RPRPatternNode *b)
 			return rprPatternChildrenEqual(a->children, b->children);
 	}
 
-	return false;				/* keep compiler quiet */
+	pg_unreachable();
+	return false;
 }
 
 /*
@@ -993,7 +994,8 @@ optimizeRPRPattern(RPRPatternNode *pattern)
 			return optimizeGroupPattern(pattern);
 	}
 
-	return pattern;				/* keep compiler quiet */
+	pg_unreachable();
+	return pattern;
 }
 
 /*
@@ -1450,7 +1452,8 @@ fillRPRPattern(RPRPatternNode *node, RPRPattern *pat, int *idx, RPRDepth depth)
 			return fillRPRPatternAlt(node, pat, idx, depth);
 	}
 
-	return false;				/* unreachable */
+	pg_unreachable();
+	return false;
 }
 
 /*
@@ -1955,10 +1958,11 @@ buildRPRPattern(RPRPatternNode *pattern, List *defineVariableList,
 	int			numElements;
 	RPRDepth	maxDepth;
 	int			idx;
-	bool		hasLimitedFrame;
 
 	/* Caller must check for NULL pattern before calling */
 	Assert(pattern != NULL);
+	/* RPR is ROWS-only: transformRPR() rejects RANGE/GROUPS up front */
+	Assert(frameOptions & FRAMEOPTION_ROWS);
 
 	/* Optimize the pattern tree */
 	optimized = optimizeRPRPattern(copyObject(pattern));
@@ -1997,10 +2001,8 @@ buildRPRPattern(RPRPatternNode *pattern, List *defineVariableList,
 	 * absorption semantics - older contexts don't necessarily produce longer
 	 * matches when frame limits apply differently to each context.
 	 */
-	hasLimitedFrame = (frameOptions & FRAMEOPTION_ROWS) &&
-		!(frameOptions & FRAMEOPTION_END_UNBOUNDED_FOLLOWING);
-
-	if (rpSkipTo == ST_PAST_LAST_ROW && !hasLimitedFrame &&
+	if (rpSkipTo == ST_PAST_LAST_ROW &&
+		(frameOptions & FRAMEOPTION_END_UNBOUNDED_FOLLOWING) &&
 		!hasMatchStartDependent)
 	{
 		/* Runtime conditions met - check structural absorbability */
-- 
2.50.1 (Apple Git-155)