From: Fujii Masao <fujii@postgresql.org>
Date: Fri, 4 Jul 2025 00:03:58 +0000 (+0900)
Subject: Speed up truncation of temporary relations.
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=refs%2Fheads%2Fmaster;p=thirdparty%2Fpostgresql.git

Speed up truncation of temporary relations.

Previously, truncating a temporary relation required scanning the entire
local buffer pool once per relation fork to invalidate buffers. This could
be slow, especially with a large local buffers, as the scan was repeated
multiple times.

A similar issue with regular tables (shared buffers) was addressed in
commit 6d05086c0a7 by scanning the buffer pool only once for all forks.

This commit applies the same optimization to temporary relations,
improving truncation performance.

Author: Daniil Davydov <3danissimo@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: Maxim Orlov <orlovmg@gmail.com>
Discussion: https://postgr.es/m/CAJDiXggNqsJOH7C5co4jA8nDk8vw-=sokyh5s1_TENWnC6Ofcg@mail.gmail.com
---

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 667aa0c0c78..bd68d7e0ca9 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -4550,11 +4550,9 @@ DropRelationBuffers(SMgrRelation smgr_reln, ForkNumber *forkNum,
 	if (RelFileLocatorBackendIsTemp(rlocator))
 	{
 		if (rlocator.backend == MyProcNumber)
-		{
-			for (j = 0; j < nforks; j++)
-				DropRelationLocalBuffers(rlocator.locator, forkNum[j],
-										 firstDelBlock[j]);
-		}
+			DropRelationLocalBuffers(rlocator.locator, forkNum, nforks,
+									 firstDelBlock);
+
 		return;
 	}
 
diff --git a/src/backend/storage/buffer/localbuf.c b/src/backend/storage/buffer/localbuf.c
index ba26627f7b0..3da9c41ee1d 100644
--- a/src/backend/storage/buffer/localbuf.c
+++ b/src/backend/storage/buffer/localbuf.c
@@ -660,10 +660,11 @@ InvalidateLocalBuffer(BufferDesc *bufHdr, bool check_unreferenced)
  *		See DropRelationBuffers in bufmgr.c for more notes.
  */
 void
-DropRelationLocalBuffers(RelFileLocator rlocator, ForkNumber forkNum,
-						 BlockNumber firstDelBlock)
+DropRelationLocalBuffers(RelFileLocator rlocator, ForkNumber *forkNum,
+						 int nforks, BlockNumber *firstDelBlock)
 {
 	int			i;
+	int			j;
 
 	for (i = 0; i < NLocBuffer; i++)
 	{
@@ -672,12 +673,18 @@ DropRelationLocalBuffers(RelFileLocator rlocator, ForkNumber forkNum,
 
 		buf_state = pg_atomic_read_u32(&bufHdr->state);
 
-		if ((buf_state & BM_TAG_VALID) &&
-			BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator) &&
-			BufTagGetForkNum(&bufHdr->tag) == forkNum &&
-			bufHdr->tag.blockNum >= firstDelBlock)
+		if (!(buf_state & BM_TAG_VALID) ||
+			!BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator))
+			continue;
+
+		for (j = 0; j < nforks; j++)
 		{
-			InvalidateLocalBuffer(bufHdr, true);
+			if (BufTagGetForkNum(&bufHdr->tag) == forkNum[j] &&
+				bufHdr->tag.blockNum >= firstDelBlock[j])
+			{
+				InvalidateLocalBuffer(bufHdr, true);
+				break;
+			}
 		}
 	}
 }
diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h
index 0dec7d93b3b..52a71b138f7 100644
--- a/src/include/storage/buf_internals.h
+++ b/src/include/storage/buf_internals.h
@@ -486,8 +486,8 @@ extern bool StartLocalBufferIO(BufferDesc *bufHdr, bool forInput, bool nowait);
 extern void FlushLocalBuffer(BufferDesc *bufHdr, SMgrRelation reln);
 extern void InvalidateLocalBuffer(BufferDesc *bufHdr, bool check_unreferenced);
 extern void DropRelationLocalBuffers(RelFileLocator rlocator,
-									 ForkNumber forkNum,
-									 BlockNumber firstDelBlock);
+									 ForkNumber *forkNum, int nforks,
+									 BlockNumber *firstDelBlock);
 extern void DropRelationAllLocalBuffers(RelFileLocator rlocator);
 extern void AtEOXact_LocalBuffers(bool isCommit);