1 files changed, 22 insertions, 29 deletions

diff --git a/src/backend/access/gin/ginvacuum.c b/src/backend/access/gin/ginvacuum.c
index b84d3a30de3..e6241850e1f 100644
--- a/src/backend/access/gin/ginvacuum.c
+++ b/src/backend/access/gin/ginvacuum.c
@@ -237,6 +237,9 @@ ginVacuumPostingTreeLeaves(GinVacuumState *gvs, BlockNumber blkno, bool isRoot,
 	return hasVoidPage;
 }
 
+/*
+ * Delete a posting tree page.
+ */
 static void
 ginDeletePage(GinVacuumState *gvs, BlockNumber deleteBlkno, BlockNumber leftBlkno,
 			  BlockNumber parentBlkno, OffsetNumber myoff, bool isParentRoot)
@@ -246,39 +249,35 @@ ginDeletePage(GinVacuumState *gvs, BlockNumber deleteBlkno, BlockNumber leftBlkn
 	Buffer		pBuffer;
 	Page		page,
 				parentPage;
+	BlockNumber	rightlink;
 
+	/*
+	 * Lock the pages in the same order as an insertion would, to avoid
+	 * deadlocks: left, then right, then parent.
+	 */
+	lBuffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, leftBlkno,
+								 RBM_NORMAL, gvs->strategy);
 	dBuffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, deleteBlkno,
 								 RBM_NORMAL, gvs->strategy);
-
-	if (leftBlkno != InvalidBlockNumber)
-		lBuffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, leftBlkno,
-									 RBM_NORMAL, gvs->strategy);
-	else
-		lBuffer = InvalidBuffer;
-
 	pBuffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, parentBlkno,
 								 RBM_NORMAL, gvs->strategy);
 
+	LockBuffer(lBuffer, GIN_EXCLUSIVE);
 	LockBuffer(dBuffer, GIN_EXCLUSIVE);
 	if (!isParentRoot)			/* parent is already locked by
 								 * LockBufferForCleanup() */
 		LockBuffer(pBuffer, GIN_EXCLUSIVE);
-	if (leftBlkno != InvalidBlockNumber)
-		LockBuffer(lBuffer, GIN_EXCLUSIVE);
 
 	START_CRIT_SECTION();
 
-	if (leftBlkno != InvalidBlockNumber)
-	{
-		BlockNumber rightlink;
-
-		page = BufferGetPage(dBuffer);
-		rightlink = GinPageGetOpaque(page)->rightlink;
+	/* Unlink the page by changing left sibling's rightlink */
+	page = BufferGetPage(dBuffer);
+	rightlink = GinPageGetOpaque(page)->rightlink;
 
-		page = BufferGetPage(lBuffer);
-		GinPageGetOpaque(page)->rightlink = rightlink;
-	}
+	page = BufferGetPage(lBuffer);
+	GinPageGetOpaque(page)->rightlink = rightlink;
 
+	/* Delete downlink from parent */
 	parentPage = BufferGetPage(pBuffer);
 #ifdef USE_ASSERT_CHECKING
 	do
@@ -360,10 +359,7 @@ ginDeletePage(GinVacuumState *gvs, BlockNumber deleteBlkno, BlockNumber leftBlkn
 	if (!isParentRoot)
 		LockBuffer(pBuffer, GIN_UNLOCK);
 	ReleaseBuffer(pBuffer);
-
-	if (leftBlkno != InvalidBlockNumber)
-		UnlockReleaseBuffer(lBuffer);
-
+	UnlockReleaseBuffer(lBuffer);
 	UnlockReleaseBuffer(dBuffer);
 
 	END_CRIT_SECTION();
@@ -431,15 +427,12 @@ ginScanToDelete(GinVacuumState *gvs, BlockNumber blkno, bool isRoot, DataPageDel
 
 	if (GinPageGetOpaque(page)->maxoff < FirstOffsetNumber)
 	{
-		if (!(me->leftBlkno == InvalidBlockNumber && GinPageRightMost(page)))
+		/* we never delete the left- or rightmost branch */
+		if (me->leftBlkno != InvalidBlockNumber && !GinPageRightMost(page))
 		{
-			/* we never delete right most branch */
 			Assert(!isRoot);
-			if (GinPageGetOpaque(page)->maxoff < FirstOffsetNumber)
-			{
-				ginDeletePage(gvs, blkno, me->leftBlkno, me->parent->blkno, myoff, me->parent->isRoot);
-				meDelete = TRUE;
-			}
+			ginDeletePage(gvs, blkno, me->leftBlkno, me->parent->blkno, myoff, me->parent->isRoot);
+			meDelete = TRUE;
 		}
 	}