Use REGBUF_NO_CHANGE at one more place in the hash index.

Commit 00d7fb5e2e started to use REGBUF_NO_CHANGE at a few places in the
code where we register the buffer before marking it dirty but missed
updating one of the code flows in the hash index where we free the overflow
page without any live tuples on it.

Author: Amit Kapila and Hayato Kuroda
Discussion: http://postgr.es/m/f045c8f7-ee24-ead6-3679-c04a43d21351@gmail.com

2 files changed, 22 insertions, 2 deletions

diff --git a/src/backend/access/hash/hash_xlog.c b/src/backend/access/hash/hash_xlog.c
index e8e06c62a95..40debf40288 100644
--- a/src/backend/access/hash/hash_xlog.c
+++ b/src/backend/access/hash/hash_xlog.c
@@ -655,7 +655,10 @@ hash_xlog_squeeze_page(XLogReaderState *record)
 		 */
 		(void) XLogReadBufferForRedoExtended(record, 0, RBM_NORMAL, true, &bucketbuf);
 
-		action = XLogReadBufferForRedo(record, 1, &writebuf);
+		if (xldata->ntups > 0 || xldata->is_prev_bucket_same_wrt)
+			action = XLogReadBufferForRedo(record, 1, &writebuf);
+		else
+			action = BLK_NOTFOUND;
 	}
 
 	/* replay the record for adding entries in overflow buffer */
diff --git a/src/backend/access/hash/hashovfl.c b/src/backend/access/hash/hashovfl.c
index 9d1ff20b922..2bd4432265c 100644
--- a/src/backend/access/hash/hashovfl.c
+++ b/src/backend/access/hash/hashovfl.c
@@ -668,14 +668,31 @@ _hash_freeovflpage(Relation rel, Buffer bucketbuf, Buffer ovflbuf,
 			XLogRegisterBuffer(0, bucketbuf, flags);
 		}
 
-		XLogRegisterBuffer(1, wbuf, REGBUF_STANDARD);
 		if (xlrec.ntups > 0)
 		{
+			XLogRegisterBuffer(1, wbuf, REGBUF_STANDARD);
 			XLogRegisterBufData(1, (char *) itup_offsets,
 								nitups * sizeof(OffsetNumber));
 			for (i = 0; i < nitups; i++)
 				XLogRegisterBufData(1, (char *) itups[i], tups_size[i]);
 		}
+		else if (xlrec.is_prim_bucket_same_wrt || xlrec.is_prev_bucket_same_wrt)
+		{
+			uint8		wbuf_flags;
+
+			/*
+			 * A write buffer needs to be registered even if no tuples are
+			 * added to it to ensure that we can acquire a cleanup lock on it
+			 * if it is the same as primary bucket buffer or update the
+			 * nextblkno if it is same as the previous bucket buffer.
+			 */
+			Assert(xlrec.ntups == 0);
+
+			wbuf_flags = REGBUF_STANDARD;
+			if (!xlrec.is_prev_bucket_same_wrt)
+				wbuf_flags |= REGBUF_NO_CHANGE;
+			XLogRegisterBuffer(1, wbuf, wbuf_flags);
+		}
 
 		XLogRegisterBuffer(2, ovflbuf, REGBUF_STANDARD);