hio: Release extension lock before initializing page / pinning VM

anarazel · anarazel · commit 14f98e0af996 · 2023-04-01T17:50:18.000-07:00
PageInit() while holding the extension lock is unnecessary after 0d1fe9f started to use RBM_ZERO_AND_LOCK - nobody can look at the new page before we release the page lock. PageInit() zeroes the page, which isn't that cheap, so deferring it until after the extension lock is released seems like a good idea. Doing visibilitymap_pin() while holding the extension lock, introduced in 7db0cd2, looks like an accident. Due to the restrictions on HEAP_INSERT_FROZEN it's unlikely to be a performance issue, but it still seems better to move it out. We also are doing the visibilitymap_pin() while holding the buffer lock, which will be fixed in a separate commit. Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi> Discussion: http://postgr.es/m/419312fd-9255-078c-c3e3-f0525f911d7f@iki.fi
diff --git a/src/backend/access/heap/hio.c b/src/backend/access/heap/hio.c
@@ -623,6 +623,13 @@ RelationGetBufferForTuple(Relation relation, Size len,
 	 */
 	buffer = ReadBufferBI(relation, P_NEW, RBM_ZERO_AND_LOCK, bistate);
 
+	/*
+	 * Release the file-extension lock; it's now OK for someone else to extend
+	 * the relation some more.
+	 */
+	if (needLock)
+		UnlockRelationForExtension(relation, ExclusiveLock);
+
 	/*
 	 * We need to initialize the empty new page.  Double-check that it really
 	 * is empty (this should never happen, but if it does we don't want to
@@ -647,13 +654,6 @@ RelationGetBufferForTuple(Relation relation, Size len,
 		visibilitymap_pin(relation, BufferGetBlockNumber(buffer), vmbuffer);
 	}
 
-	/*
-	 * Release the file-extension lock; it's now OK for someone else to extend
-	 * the relation some more.
-	 */
-	if (needLock)
-		UnlockRelationForExtension(relation, ExclusiveLock);
-
 	/*
 	 * Lock the other buffer. It's guaranteed to be of a lower page number
 	 * than the new page. To conform with the deadlock prevent rules, we ought
