v16-0008-Make-buffer-hit-helper.patch

From 0f6cc4967a240b6fabd2b39e45068051b3ad8424 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Fri, 23 Jan 2026 13:54:02 -0500
Subject: [PATCH v16 08/17] Make buffer hit helper

Already two places count buffer hits, requiring quite a few lines of
code since we do accounting in so many places. Future commits will add
more locations, so refactor into a helper.

Note: I (pgeoghean) have changed this from Melanie's original by
inlining the helper function:

https://postgr.es/m/CAH2-Wzk02vPjsJPx7EGNmgvsKKgyHn=XtGjJcPE+eQTP3xQt7w@mail.gmail.com
---
 src/backend/storage/buffer/bufmgr.c | 111 ++++++++++++++--------------
 1 file changed, 56 insertions(+), 55 deletions(-)

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 2a95517a3..6cad27137 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -648,6 +648,10 @@ static inline BufferDesc *BufferAlloc(SMgrRelation smgr,
 									  bool *foundPtr, IOContext io_context);
 static bool AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress);
 static void CheckReadBuffersOperation(ReadBuffersOperation *operation, bool is_complete);
+static inline void ProcessBufferHit(BufferAccessStrategy strategy,
+									Relation rel, char persistence,
+									SMgrRelation smgr, ForkNumber forknum,
+									BlockNumber blocknum);
 static Buffer GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context);
 static void FlushUnlockedBuffer(BufferDesc *buf, SMgrRelation reln,
 								IOObject io_object, IOContext io_context);
@@ -1226,8 +1230,6 @@ PinBufferForBlock(Relation rel,
 				  bool *foundPtr)
 {
 	BufferDesc *bufHdr;
-	IOContext	io_context;
-	IOObject	io_object;
 
 	Assert(blockNum != P_NEW);
 
@@ -1236,17 +1238,6 @@ PinBufferForBlock(Relation rel,
 			persistence == RELPERSISTENCE_PERMANENT ||
 			persistence == RELPERSISTENCE_UNLOGGED));
 
-	if (persistence == RELPERSISTENCE_TEMP)
-	{
-		io_context = IOCONTEXT_NORMAL;
-		io_object = IOOBJECT_TEMP_RELATION;
-	}
-	else
-	{
-		io_context = IOContextForStrategy(strategy);
-		io_object = IOOBJECT_RELATION;
-	}
-
 	TRACE_POSTGRESQL_BUFFER_READ_START(forkNum, blockNum,
 									   smgr->smgr_rlocator.locator.spcOid,
 									   smgr->smgr_rlocator.locator.dbOid,
@@ -1254,18 +1245,11 @@ PinBufferForBlock(Relation rel,
 									   smgr->smgr_rlocator.backend);
 
 	if (persistence == RELPERSISTENCE_TEMP)
-	{
 		bufHdr = LocalBufferAlloc(smgr, forkNum, blockNum, foundPtr);
-		if (*foundPtr)
-			pgBufferUsage.local_blks_hit++;
-	}
 	else
-	{
 		bufHdr = BufferAlloc(smgr, persistence, forkNum, blockNum,
-							 strategy, foundPtr, io_context);
-		if (*foundPtr)
-			pgBufferUsage.shared_blks_hit++;
-	}
+							 strategy, foundPtr, IOContextForStrategy(strategy));
+
 	if (rel)
 	{
 		/*
@@ -1274,22 +1258,10 @@ PinBufferForBlock(Relation rel,
 		 * zeroed instead), the per-relation stats always count them.
 		 */
 		pgstat_count_buffer_read(rel);
-		if (*foundPtr)
-			pgstat_count_buffer_hit(rel);
 	}
-	if (*foundPtr)
-	{
-		pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
-		if (VacuumCostActive)
-			VacuumCostBalance += VacuumCostPageHit;
 
-		TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
-										  smgr->smgr_rlocator.locator.spcOid,
-										  smgr->smgr_rlocator.locator.dbOid,
-										  smgr->smgr_rlocator.locator.relNumber,
-										  smgr->smgr_rlocator.backend,
-										  true);
-	}
+	if (*foundPtr)
+		ProcessBufferHit(strategy, rel, persistence, smgr, forkNum, blockNum);
 
 	return BufferDescriptorGetBuffer(bufHdr);
 }
@@ -1695,6 +1667,51 @@ ReadBuffersCanStartIO(Buffer buffer, bool nowait)
 	return ReadBuffersCanStartIOOnce(buffer, nowait);
 }
 
+/*
+ * We track various stats related to buffer hits. Because this is done in a
+ * few separate places, this helper exists for convenience.
+ */
+static inline void
+ProcessBufferHit(BufferAccessStrategy strategy,
+				 Relation rel, char persistence, SMgrRelation smgr,
+				 ForkNumber forknum, BlockNumber blocknum)
+{
+	IOContext	io_context;
+	IOObject	io_object;
+
+	if (persistence == RELPERSISTENCE_TEMP)
+	{
+		io_context = IOCONTEXT_NORMAL;
+		io_object = IOOBJECT_TEMP_RELATION;
+	}
+	else
+	{
+		io_context = IOContextForStrategy(strategy);
+		io_object = IOOBJECT_RELATION;
+	}
+
+	TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum,
+									  blocknum,
+									  smgr->smgr_rlocator.locator.spcOid,
+									  smgr->smgr_rlocator.locator.dbOid,
+									  smgr->smgr_rlocator.locator.relNumber,
+									  smgr->smgr_rlocator.backend,
+									  true);
+
+	if (persistence == RELPERSISTENCE_TEMP)
+		pgBufferUsage.local_blks_hit += 1;
+	else
+		pgBufferUsage.shared_blks_hit += 1;
+
+	if (rel)
+		pgstat_count_buffer_hit(rel);
+
+	pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
+
+	if (VacuumCostActive)
+		VacuumCostBalance += VacuumCostPageHit;
+}
+
 /*
  * Helper for WaitReadBuffers() that processes the results of a readv
  * operation, raising an error if necessary.
@@ -1990,25 +2007,9 @@ AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress)
 		 * must have started out as a miss in PinBufferForBlock(). The other
 		 * backend will track this as a 'read'.
 		 */
-		TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, blocknum + operation->nblocks_done,
-										  operation->smgr->smgr_rlocator.locator.spcOid,
-										  operation->smgr->smgr_rlocator.locator.dbOid,
-										  operation->smgr->smgr_rlocator.locator.relNumber,
-										  operation->smgr->smgr_rlocator.backend,
-										  true);
-
-		if (persistence == RELPERSISTENCE_TEMP)
-			pgBufferUsage.local_blks_hit += 1;
-		else
-			pgBufferUsage.shared_blks_hit += 1;
-
-		if (operation->rel)
-			pgstat_count_buffer_hit(operation->rel);
-
-		pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
-
-		if (VacuumCostActive)
-			VacuumCostBalance += VacuumCostPageHit;
+		ProcessBufferHit(operation->strategy, operation->rel, persistence,
+						 operation->smgr, forknum,
+						 blocknum + operation->nblocks_done);
 	}
 	else
 	{
-- 
2.53.0