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 6d05086 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 <[email protected]>
Reviewed-by: Michael Paquier <[email protected]>
Reviewed-by: Fujii Masao <[email protected]>
Reviewed-by: Dilip Kumar <[email protected]>
Reviewed-by: Maxim Orlov <[email protected]>
Discussion: https://postgr.es/m/CAJDiXggNqsJOH7C5co4jA8nDk8vw-=sokyh5s1_TENWnC6Ofcg@mail.gmail.com

Author: MasaoFujii

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;
 	}
 

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;
+			}
 		}
 	}
 }

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);