v3-0002-Optimize-copy-storage-from-source-to-destination.patch

From 4324772a967515b4aa097c3a67ed35348373281c Mon Sep 17 00:00:00 2001
From: Dilip Kumar <dilip.kumar@enterprisedb.com>
Date: Fri, 5 Aug 2022 11:25:23 +0530
Subject: [PATCH v3 2/2] Optimize copy storage from source to destination

Instead of extending block at a time directly bulkextend the destination
relation and then just perform the block level copy.
---
 src/backend/storage/buffer/bufmgr.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 9c1bd508d3..377389e762 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -3710,6 +3710,7 @@ RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
 	Page		srcPage;
 	Page		dstPage;
 	bool		use_wal;
+	char		buffer[BLCKSZ];
 	BlockNumber nblocks;
 	BlockNumber blkno;
 	BufferAccessStrategy bstrategy_src;
@@ -3730,6 +3731,14 @@ RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
 	if (nblocks == 0)
 		return;
 
+	/*
+	 * Bulk extend the destination relation of the same size as the source
+	 * relation before starting to copy block by block.
+	 */
+	memset(buffer, 0, BLCKSZ);
+	smgrextend(smgropen(dstlocator, InvalidBackendId), forkNum, nblocks - 1,
+			   buffer, true);
+
 	/* This is a bulk operation, so use buffer access strategies. */
 	bstrategy_src = GetAccessStrategy(BAS_BULKREAD);
 	bstrategy_dst = GetAccessStrategy(BAS_BULKWRITE);
@@ -3747,7 +3756,7 @@ RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
 		srcPage = BufferGetPage(srcBuf);
 
 		/* Use P_NEW to extend the destination relation. */
-		dstBuf = ReadBufferWithoutRelcache(dstlocator, forkNum, P_NEW,
+		dstBuf = ReadBufferWithoutRelcache(dstlocator, forkNum, blkno,
 										   RBM_NORMAL, bstrategy_dst,
 										   permanent);
 		LockBuffer(dstBuf, BUFFER_LOCK_EXCLUSIVE);
-- 
2.23.0