1 files changed, 21 insertions, 10 deletions

diff --git a/src/backend/access/heap/hio.c b/src/backend/access/heap/hio.c
index 3da0b49ccc4..985c4c47779 100644
--- a/src/backend/access/heap/hio.c
+++ b/src/backend/access/heap/hio.c
@@ -204,7 +204,8 @@ RelationAddExtraBlocks(Relation relation, BulkInsertState bistate)
 		/*
 		 * Extend by one page.  This should generally match the main-line
 		 * extension code in RelationGetBufferForTuple, except that we hold
-		 * the relation extension lock throughout.
+		 * the relation extension lock throughout, and we don't immediately
+		 * initialize the page (see below).
 		 */
 		buffer = ReadBufferBI(relation, P_NEW, bistate);
 
@@ -216,18 +217,16 @@ RelationAddExtraBlocks(Relation relation, BulkInsertState bistate)
 				 BufferGetBlockNumber(buffer),
 				 RelationGetRelationName(relation));
 
-		PageInit(page, BufferGetPageSize(buffer), 0);
-
 		/*
-		 * We mark all the new buffers dirty, but do nothing to write them
-		 * out; they'll probably get used soon, and even if they are not, a
-		 * crash will leave an okay all-zeroes page on disk.
+		 * Add the page to the FSM without initializing. If we were to
+		 * initialize here the page would potentially get flushed out to disk
+		 * before we add any useful content. There's no guarantee that that'd
+		 * happen before a potential crash, so we need to deal with
+		 * uninitialized pages anyway, thus avoid the potential for
+		 * unnecessary writes.
 		 */
-		MarkBufferDirty(buffer);
-
-		/* we'll need this info below */
 		blockNum = BufferGetBlockNumber(buffer);
-		freespace = PageGetHeapFreeSpace(page);
+		freespace = BufferGetPageSize(buffer) - SizeOfPageHeaderData;
 
 		UnlockReleaseBuffer(buffer);
 
@@ -479,6 +478,18 @@ loop:
 		 * we're done.
 		 */
 		page = BufferGetPage(buffer);
+
+		/*
+		 * Initialize page, it'll be used soon.  We could avoid dirtying the
+		 * buffer here, and rely on the caller to do so whenever it puts a
+		 * tuple onto the page, but there seems not much benefit in doing so.
+		 */
+		if (PageIsNew(page))
+		{
+			PageInit(page, BufferGetPageSize(buffer), 0);
+			MarkBufferDirty(buffer);
+		}
+
 		pageFreeSpace = PageGetHeapFreeSpace(page);
 		if (len + saveFreeSpace <= pageFreeSpace)
 		{