Predicate locking in GIN index

Predicate locks are used on per page basis only if fastupdate = off, in
opposite case predicate lock on pending list will effectively lock whole index,
to reduce locking overhead, just lock a relation. Entry and posting trees are
essentially B-tree, so locks are acquired on leaf pages only.

Author: Shubham Barai with some editorization by me and Dmitry Ivanov
Review by: Alexander Korotkov, Dmitry Ivanov, Fedor Sigaev
Discussion: https://www.postgresql.org/message-id/flat/CALxAEPt5sWW+EwTaKUGFL5_XFcZ0MuGBcyJ70oqbWqr42YKR8Q@mail.gmail.com

11 files changed, 1054 insertions, 18 deletions

diff --git a/src/backend/access/gin/ginbtree.c b/src/backend/access/gin/ginbtree.c
index 37070b3b729..095b1192cb4 100644
--- a/src/backend/access/gin/ginbtree.c
+++ b/src/backend/access/gin/ginbtree.c
@@ -17,6 +17,7 @@
 #include "access/gin_private.h"
 #include "access/ginxlog.h"
 #include "access/xloginsert.h"
+#include "storage/predicate.h"
 #include "miscadmin.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
@@ -515,6 +516,19 @@ ginPlaceToPage(GinBtree btree, GinBtreeStack *stack,
 			btree->fillRoot(btree, newrootpg,
 							BufferGetBlockNumber(lbuffer), newlpage,
 							BufferGetBlockNumber(rbuffer), newrpage);
+
+			if (GinPageIsLeaf(BufferGetPage(stack->buffer)))
+			{
+
+				PredicateLockPageSplit(btree->index,
+						BufferGetBlockNumber(stack->buffer),
+						BufferGetBlockNumber(lbuffer));
+
+				PredicateLockPageSplit(btree->index,
+						BufferGetBlockNumber(stack->buffer),
+						BufferGetBlockNumber(rbuffer));
+			}
+
 		}
 		else
 		{
@@ -524,6 +538,14 @@ ginPlaceToPage(GinBtree btree, GinBtreeStack *stack,
 			GinPageGetOpaque(newrpage)->rightlink = savedRightLink;
 			GinPageGetOpaque(newlpage)->flags |= GIN_INCOMPLETE_SPLIT;
 			GinPageGetOpaque(newlpage)->rightlink = BufferGetBlockNumber(rbuffer);
+
+			if (GinPageIsLeaf(BufferGetPage(stack->buffer)))
+			{
+
+				PredicateLockPageSplit(btree->index,
+						BufferGetBlockNumber(stack->buffer),
+						BufferGetBlockNumber(rbuffer));
+			}
 		}
 
 		/*
diff --git a/src/backend/access/gin/gindatapage.c b/src/backend/access/gin/gindatapage.c
index f9daaba52eb..642ca1a2c73 100644
--- a/src/backend/access/gin/gindatapage.c
+++ b/src/backend/access/gin/gindatapage.c
@@ -19,6 +19,7 @@
 #include "access/xloginsert.h"
 #include "lib/ilist.h"
 #include "miscadmin.h"
+#include "storage/predicate.h"
 #include "utils/rel.h"
 
 /*
@@ -1759,7 +1760,7 @@ leafRepackItems(disassembledLeaf *leaf, ItemPointer remaining)
  */
 BlockNumber
 createPostingTree(Relation index, ItemPointerData *items, uint32 nitems,
-				  GinStatsData *buildStats)
+				  GinStatsData *buildStats, Buffer entrybuffer)
 {
 	BlockNumber blkno;
 	Buffer		buffer;
@@ -1810,6 +1811,12 @@ createPostingTree(Relation index, ItemPointerData *items, uint32 nitems,
 	page = BufferGetPage(buffer);
 	blkno = BufferGetBlockNumber(buffer);
 
+	/*
+	 * Copy a predicate lock from entry tree leaf (containing posting list)
+	 * to  posting tree.
+	 */
+	PredicateLockPageSplit(index, BufferGetBlockNumber(entrybuffer), blkno);
+
 	START_CRIT_SECTION();
 
 	PageRestoreTempPage(tmppage, page);
@@ -1904,6 +1911,7 @@ ginInsertItemPointers(Relation index, BlockNumber rootBlkno,
 		btree.itemptr = insertdata.items[insertdata.curitem];
 		stack = ginFindLeafPage(&btree, false, NULL);
 
+		GinCheckForSerializableConflictIn(btree.index, NULL, stack->buffer);
 		ginInsertValue(&btree, stack, &insertdata, buildStats);
 	}
 }
diff --git a/src/backend/access/gin/ginget.c b/src/backend/access/gin/ginget.c
index 6fe67f346df..0e984166fa8 100644
--- a/src/backend/access/gin/ginget.c
+++ b/src/backend/access/gin/ginget.c
@@ -17,8 +17,10 @@
 #include "access/gin_private.h"
 #include "access/relscan.h"
 #include "miscadmin.h"
+#include "storage/predicate.h"
 #include "utils/datum.h"
 #include "utils/memutils.h"
+#include "utils/rel.h"
 
 /* GUC parameter */
 int			GinFuzzySearchLimit = 0;
@@ -34,10 +36,24 @@ typedef struct pendingPosition
 
 
 /*
+ * Place predicate lock on GIN page if needed.
+ */
+static void
+GinPredicateLockPage(Relation index, BlockNumber blkno, Snapshot snapshot)
+{
+	/*
+	 * When fast update is on then no need in locking pages, because we
+	 * anyway need to lock the whole index.
+	 */
+	if (!GinGetUseFastUpdate(index))
+			PredicateLockPage(index, blkno, snapshot);
+}
+
+/*
  * Goes to the next page if current offset is outside of bounds
  */
 static bool
-moveRightIfItNeeded(GinBtreeData *btree, GinBtreeStack *stack)
+moveRightIfItNeeded(GinBtreeData *btree, GinBtreeStack *stack, Snapshot snapshot)
 {
 	Page		page = BufferGetPage(stack->buffer);
 
@@ -52,6 +68,7 @@ moveRightIfItNeeded(GinBtreeData *btree, GinBtreeStack *stack)
 		stack->buffer = ginStepRight(stack->buffer, btree->index, GIN_SHARE);
 		stack->blkno = BufferGetBlockNumber(stack->buffer);
 		stack->off = FirstOffsetNumber;
+		GinPredicateLockPage(btree->index, stack->blkno, snapshot);
 	}
 
 	return true;
@@ -73,6 +90,7 @@ scanPostingTree(Relation index, GinScanEntry scanEntry,
 	/* Descend to the leftmost leaf page */
 	stack = ginScanBeginPostingTree(&btree, index, rootPostingTree, snapshot);
 	buffer = stack->buffer;
+
 	IncrBufferRefCount(buffer); /* prevent unpin in freeGinBtreeStack */
 
 	freeGinBtreeStack(stack);
@@ -82,6 +100,11 @@ scanPostingTree(Relation index, GinScanEntry scanEntry,
 	 */
 	for (;;)
 	{
+		/*
+		 * Predicate lock each leaf page in posting tree
+		 */
+		GinPredicateLockPage(index, BufferGetBlockNumber(buffer), snapshot);
+
 		page = BufferGetPage(buffer);
 		if ((GinPageGetOpaque(page)->flags & GIN_DELETED) == 0)
 		{
@@ -131,6 +154,12 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
 	attnum = scanEntry->attnum;
 	attr = TupleDescAttr(btree->ginstate->origTupdesc, attnum - 1);
 
+	/*
+	 * Predicate lock entry leaf page, following pages will be locked by
+	 * moveRightIfItNeeded()
+	 */
+	GinPredicateLockPage(btree->index, stack->buffer, snapshot);
+
 	for (;;)
 	{
 		Page		page;
@@ -141,7 +170,7 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
 		/*
 		 * stack->off points to the interested entry, buffer is already locked
 		 */
-		if (moveRightIfItNeeded(btree, stack) == false)
+		if (moveRightIfItNeeded(btree, stack, snapshot) == false)
 			return true;
 
 		page = BufferGetPage(stack->buffer);
@@ -250,7 +279,7 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
 				Datum		newDatum;
 				GinNullCategory newCategory;
 
-				if (moveRightIfItNeeded(btree, stack) == false)
+				if (moveRightIfItNeeded(btree, stack, snapshot) == false)
 					elog(ERROR, "lost saved point in index");	/* must not happen !!! */
 
 				page = BufferGetPage(stack->buffer);
@@ -323,6 +352,7 @@ restartScanEntry:
 						ginstate);
 	stackEntry = ginFindLeafPage(&btreeEntry, true, snapshot);
 	page = BufferGetPage(stackEntry->buffer);
+
 	/* ginFindLeafPage() will have already checked snapshot age. */
 	needUnlock = true;
 
@@ -370,6 +400,10 @@ restartScanEntry:
 	{
 		IndexTuple	itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, stackEntry->off));
 
+		/* Predicate lock visited entry leaf page */
+		GinPredicateLockPage(ginstate->index,
+							 BufferGetBlockNumber(stackEntry->buffer), snapshot);
+
 		if (GinIsPostingTree(itup))
 		{
 			BlockNumber rootPostingTree = GinGetPostingTree(itup);
@@ -392,6 +426,12 @@ restartScanEntry:
 			entry->buffer = stack->buffer;
 
 			/*
+			 * Predicate lock visited posting tree page, following pages
+			 * will be locked by moveRightIfItNeeded or entryLoadMoreItems
+			 */
+			GinPredicateLockPage(ginstate->index, BufferGetBlockNumber(entry->buffer), snapshot);
+
+			/*
 			 * We keep buffer pinned because we need to prevent deletion of
 			 * page during scan. See GIN's vacuum implementation. RefCount is
 			 * increased to keep buffer pinned after freeGinBtreeStack() call.
@@ -493,7 +533,7 @@ startScanKey(GinState *ginstate, GinScanOpaque so, GinScanKey key)
 
 		for (i = 0; i < key->nentries - 1; i++)
 		{
-			/* Pass all entries <= i as FALSE, and the rest as MAYBE */
+			/* Pass all entries <= i as false, and the rest as MAYBE */
 			for (j = 0; j <= i; j++)
 				key->entryRes[entryIndexes[j]] = GIN_FALSE;
 			for (j = i + 1; j < key->nentries; j++)
@@ -633,6 +673,8 @@ entryLoadMoreItems(GinState *ginstate, GinScanEntry entry,
 		entry->btree.fullScan = false;
 		stack = ginFindLeafPage(&entry->btree, true, snapshot);
 
+		GinPredicateLockPage(ginstate->index, BufferGetBlockNumber(stack->buffer), snapshot);
+
 		/* we don't need the stack, just the buffer. */
 		entry->buffer = stack->buffer;
 		IncrBufferRefCount(entry->buffer);
@@ -677,6 +719,10 @@ entryLoadMoreItems(GinState *ginstate, GinScanEntry entry,
 			entry->buffer = ginStepRight(entry->buffer,
 										 ginstate->index,
 										 GIN_SHARE);
+
+			GinPredicateLockPage(ginstate->index, BufferGetBlockNumber(entry->buffer), snapshot);
+
+
 			page = BufferGetPage(entry->buffer);
 		}
 		stepright = true;
@@ -1038,8 +1084,8 @@ keyGetItem(GinState *ginstate, MemoryContext tempCtx, GinScanKey key,
 	 * lossy page even when none of the other entries match.
 	 *
 	 * Our strategy is to call the tri-state consistent function, with the
-	 * lossy-page entries set to MAYBE, and all the other entries FALSE. If it
-	 * returns FALSE, none of the lossy items alone are enough for a match, so
+	 * lossy-page entries set to MAYBE, and all the other entries false. If it
+	 * returns false, none of the lossy items alone are enough for a match, so
 	 * we don't need to return a lossy-page pointer. Otherwise, return a
 	 * lossy-page pointer to indicate that the whole heap page must be
 	 * checked.  (On subsequent calls, we'll do nothing until minItem is past
@@ -1700,7 +1746,8 @@ collectMatchesForHeapRow(IndexScanDesc scan, pendingPosition *pos)
 }
 
 /*
- * Collect all matched rows from pending list into bitmap
+ * Collect all matched rows from pending list into bitmap. Also function
+ * takes PendingLockRelation if it's needed.
  */
 static void
 scanPendingInsert(IndexScanDesc scan, TIDBitmap *tbm, int64 *ntids)
@@ -1730,9 +1777,24 @@ scanPendingInsert(IndexScanDesc scan, TIDBitmap *tbm, int64 *ntids)
 	{
 		/* No pending list, so proceed with normal scan */
 		UnlockReleaseBuffer(metabuffer);
+
+		/*
+		 * If fast update is enabled, we acquire a predicate lock on the entire
+		 * relation as fast update postpones the insertion of tuples into index
+		 * structure due to which we can't detect rw conflicts.
+		 */
+		if (GinGetUseFastUpdate(scan->indexRelation))
+			PredicateLockRelation(scan->indexRelation, scan->xs_snapshot);
+
 		return;
 	}
 
+	/*
+	 * Pending list is not empty, we need to lock the index doesn't despite on
+	 * fastupdate state
+	 */
+	PredicateLockRelation(scan->indexRelation, scan->xs_snapshot);
+
 	pos.pendingBuffer = ReadBuffer(scan->indexRelation, blkno);
 	LockBuffer(pos.pendingBuffer, GIN_SHARE);
 	pos.firstOffset = FirstOffsetNumber;
diff --git a/src/backend/access/gin/gininsert.c b/src/backend/access/gin/gininsert.c
index 23f72855474..ec5eebb8484 100644
--- a/src/backend/access/gin/gininsert.c
+++ b/src/backend/access/gin/gininsert.c
@@ -22,6 +22,7 @@
 #include "storage/bufmgr.h"
 #include "storage/smgr.h"
 #include "storage/indexfsm.h"
+#include "storage/predicate.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
 
@@ -48,7 +49,7 @@ static IndexTuple
 addItemPointersToLeafTuple(GinState *ginstate,
 						   IndexTuple old,
 						   ItemPointerData *items, uint32 nitem,
-						   GinStatsData *buildStats)
+						   GinStatsData *buildStats, Buffer buffer)
 {
 	OffsetNumber attnum;
 	Datum		key;
@@ -99,7 +100,8 @@ addItemPointersToLeafTuple(GinState *ginstate,
 		postingRoot = createPostingTree(ginstate->index,
 										oldItems,
 										oldNPosting,
-										buildStats);
+										buildStats,
+										buffer);
 
 		/* Now insert the TIDs-to-be-added into the posting tree */
 		ginInsertItemPointers(ginstate->index, postingRoot,
@@ -127,7 +129,7 @@ static IndexTuple
 buildFreshLeafTuple(GinState *ginstate,
 					OffsetNumber attnum, Datum key, GinNullCategory category,
 					ItemPointerData *items, uint32 nitem,
-					GinStatsData *buildStats)
+					GinStatsData *buildStats, Buffer buffer)
 {
 	IndexTuple	res = NULL;
 	GinPostingList *compressedList;
@@ -157,7 +159,7 @@ buildFreshLeafTuple(GinState *ginstate,
 		 * Initialize a new posting tree with the TIDs.
 		 */
 		postingRoot = createPostingTree(ginstate->index, items, nitem,
-										buildStats);
+										buildStats, buffer);
 
 		/* And save the root link in the result tuple */
 		GinSetPostingTree(res, postingRoot);
@@ -217,17 +219,19 @@ ginEntryInsert(GinState *ginstate,
 			return;
 		}
 
+		GinCheckForSerializableConflictIn(btree.index, NULL, stack->buffer);
 		/* modify an existing leaf entry */
 		itup = addItemPointersToLeafTuple(ginstate, itup,
-										  items, nitem, buildStats);
+										  items, nitem, buildStats, stack->buffer);
 
 		insertdata.isDelete = true;
 	}
 	else
 	{
+		GinCheckForSerializableConflictIn(btree.index, NULL, stack->buffer);
 		/* no match, so construct a new leaf entry */
 		itup = buildFreshLeafTuple(ginstate, attnum, key, category,
-								   items, nitem, buildStats);
+								   items, nitem, buildStats, stack->buffer);
 	}
 
 	/* Insert the new or modified leaf tuple */
@@ -513,6 +517,18 @@ gininsert(Relation index, Datum *values, bool *isnull,
 
 		memset(&collector, 0, sizeof(GinTupleCollector));
 
+		/*
+		 * With fastupdate on each scan and each insert begin with access to
+		 * pending list, so it effectively lock entire index. In this case
+		 * we aquire predicate lock and check for conflicts over index relation,
+		 * and hope that it will reduce locking overhead.
+		 *
+		 * Do not use GinCheckForSerializableConflictIn() here, because
+		 * it will do nothing (it does actual work only with fastupdate off).
+		 * Check for conflicts for entire index.
+		 */
+		CheckForSerializableConflictIn(index, NULL, InvalidBuffer);
+
 		for (i = 0; i < ginstate->origTupdesc->natts; i++)
 			ginHeapTupleFastCollect(ginstate, &collector,
 									(OffsetNumber) (i + 1),
@@ -523,6 +539,16 @@ gininsert(Relation index, Datum *values, bool *isnull,
 	}
 	else
 	{
+		GinStatsData	stats;
+
+		/*
+		 * Fastupdate is off but if pending list isn't empty then we need to
+		 * check conflicts with PredicateLockRelation in scanPendingInsert().
+		 */
+		ginGetStats(index, &stats);
+		if (stats.nPendingPages > 0)
+			CheckForSerializableConflictIn(index, NULL, InvalidBuffer);
+
 		for (i = 0; i < ginstate->origTupdesc->natts; i++)
 			ginHeapTupleInsert(ginstate, (OffsetNumber) (i + 1),
 							   values[i], isnull[i],
diff --git a/src/backend/access/gin/ginutil.c b/src/backend/access/gin/ginutil.c
index 7bac7a12521..5632cc5a773 100644
--- a/src/backend/access/gin/ginutil.c
+++ b/src/backend/access/gin/ginutil.c
@@ -23,6 +23,7 @@
 #include "miscadmin.h"
 #include "storage/indexfsm.h"
 #include "storage/lmgr.h"
+#include "storage/predicate.h"
 #include "utils/builtins.h"
 #include "utils/index_selfuncs.h"
 #include "utils/typcache.h"
@@ -49,7 +50,7 @@ ginhandler(PG_FUNCTION_ARGS)
 	amroutine->amsearchnulls = false;
 	amroutine->amstorage = true;
 	amroutine->amclusterable = false;
-	amroutine->ampredlocks = false;
+	amroutine->ampredlocks = true;
 	amroutine->amcanparallel = false;
 	amroutine->amkeytype = InvalidOid;
 
@@ -716,3 +717,10 @@ ginUpdateStats(Relation index, const GinStatsData *stats)
 
 	END_CRIT_SECTION();
 }
+
+void
+GinCheckForSerializableConflictIn(Relation relation, HeapTuple tuple, Buffer buffer)
+{
+	if (!GinGetUseFastUpdate(relation))
+		CheckForSerializableConflictIn(relation, tuple, buffer);
+}
diff --git a/src/backend/access/gin/ginvacuum.c b/src/backend/access/gin/ginvacuum.c
index 630d6a7788c..dd8e31b8721 100644
--- a/src/backend/access/gin/ginvacuum.c
+++ b/src/backend/access/gin/ginvacuum.c
@@ -22,6 +22,7 @@
 #include "postmaster/autovacuum.h"
 #include "storage/indexfsm.h"
 #include "storage/lmgr.h"
+#include "storage/predicate.h"
 #include "utils/memutils.h"
 
 struct GinVacuumState
@@ -153,11 +154,18 @@ ginDeletePage(GinVacuumState *gvs, BlockNumber deleteBlkno, BlockNumber leftBlkn
 
 	LockBuffer(lBuffer, GIN_EXCLUSIVE);
 
+	page = BufferGetPage(dBuffer);
+	rightlink = GinPageGetOpaque(page)->rightlink;
+
+	/*
+	 * Any insert which would have gone on the leaf block will now go to its
+	 * right sibling.
+	 */
+	PredicateLockPageCombine(gvs->index, deleteBlkno, rightlink);
+
 	START_CRIT_SECTION();
 
 	/* Unlink the page by changing left sibling's rightlink */
-	page = BufferGetPage(dBuffer);
-	rightlink = GinPageGetOpaque(page)->rightlink;
 
 	page = BufferGetPage(lBuffer);
 	GinPageGetOpaque(page)->rightlink = rightlink;
diff --git a/src/backend/storage/lmgr/README-SSI b/src/backend/storage/lmgr/README-SSI
index e221241f965..9e98af23c83 100644
--- a/src/backend/storage/lmgr/README-SSI
+++ b/src/backend/storage/lmgr/README-SSI
@@ -380,6 +380,15 @@ then be trusted to ripple up to all levels and locations where
 conflicting predicate locks may exist. In case there is a page split,
 we need to copy predicate lock from an original page to all new pages.
 
+    * GIN searches acquire predicate locks only on the leaf pages
+of entry tree and posting tree. During a page split, a predicate locks are
+copied from the original page to the new page. In the same way predicate locks
+are copied from entry tree leaf page to freshly created posting tree root.
+However, when fast update is enabled, a predicate lock on the whole index
+relation is required. Fast update postpones the insertion of tuples into index
+structure by temporarily storing them into pending list. That makes us unable
+to detect r-w conflicts using page-level locks.
+
     * The effects of page splits, overflows, consolidations, and
 removals must be carefully reviewed to ensure that predicate locks
 aren't "lost" during those operations, or kept with pages which could
diff --git a/src/include/access/gin_private.h b/src/include/access/gin_private.h
index a709596a7ae..d1df3033a6d 100644
--- a/src/include/access/gin_private.h
+++ b/src/include/access/gin_private.h
@@ -103,6 +103,8 @@ extern Datum *ginExtractEntries(GinState *ginstate, OffsetNumber attnum,
 extern OffsetNumber gintuple_get_attrnum(GinState *ginstate, IndexTuple tuple);
 extern Datum gintuple_get_key(GinState *ginstate, IndexTuple tuple,
 				 GinNullCategory *category);
+extern void GinCheckForSerializableConflictIn(Relation relation,
+				 HeapTuple tuple, Buffer buffer);
 
 /* gininsert.c */
 extern IndexBuildResult *ginbuild(Relation heap, Relation index,
@@ -217,7 +219,7 @@ extern ItemPointer GinDataLeafPageGetItems(Page page, int *nitems, ItemPointerDa
 extern int	GinDataLeafPageGetItemsToTbm(Page page, TIDBitmap *tbm);
 extern BlockNumber createPostingTree(Relation index,
 				  ItemPointerData *items, uint32 nitems,
-				  GinStatsData *buildStats);
+				  GinStatsData *buildStats, Buffer entrybuffer);
 extern void GinDataPageAddPostingItem(Page page, PostingItem *data, OffsetNumber offset);
 extern void GinPageDeletePostingItem(Page page, OffsetNumber offset);
 extern void ginInsertItemPointers(Relation index, BlockNumber rootBlkno,
diff --git a/src/test/isolation/expected/predicate-gin.out b/src/test/isolation/expected/predicate-gin.out
new file mode 100644
index 00000000000..4f5501f6f01
--- /dev/null
+++ b/src/test/isolation/expected/predicate-gin.out
@@ -0,0 +1,756 @@
+Parsed test spec with 2 sessions
+
+starting permutation: rxy1 wx1 c1 rxy2 wy2 c2
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c1: commit;
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10050          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step c2: commit;
+
+starting permutation: rxy2 wy2 c2 rxy1 wx1 c1
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step c2: commit;
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10050          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c1: commit;
+
+starting permutation: rxy3 wx3 c1 rxy4 wy4 c2
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c1: commit;
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c2: commit;
+
+starting permutation: rxy4 wy4 c2 rxy3 wx3 c1
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c2: commit;
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c1: commit;
+
+starting permutation: rxy1 wx1 rxy2 c1 wy2 c2
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step c1: commit;
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+step c2: commit;
+
+starting permutation: rxy1 wx1 rxy2 wy2 c1 c2
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step c1: commit;
+step c2: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy1 wx1 rxy2 wy2 c2 c1
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step c2: commit;
+step c1: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy1 rxy2 wx1 c1 wy2 c2
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c1: commit;
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+step c2: commit;
+
+starting permutation: rxy1 rxy2 wx1 wy2 c1 c2
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step c1: commit;
+step c2: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy1 rxy2 wx1 wy2 c2 c1
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step c2: commit;
+step c1: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy1 rxy2 wy2 wx1 c1 c2
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c1: commit;
+step c2: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy1 rxy2 wy2 wx1 c2 c1
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c2: commit;
+step c1: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy1 rxy2 wy2 c2 wx1 c1
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step c2: commit;
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+step c1: commit;
+
+starting permutation: rxy2 rxy1 wx1 c1 wy2 c2
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c1: commit;
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+step c2: commit;
+
+starting permutation: rxy2 rxy1 wx1 wy2 c1 c2
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step c1: commit;
+step c2: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy2 rxy1 wx1 wy2 c2 c1
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step c2: commit;
+step c1: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy2 rxy1 wy2 wx1 c1 c2
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c1: commit;
+step c2: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy2 rxy1 wy2 wx1 c2 c1
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c2: commit;
+step c1: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy2 rxy1 wy2 c2 wx1 c1
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step c2: commit;
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+step c1: commit;
+
+starting permutation: rxy2 wy2 rxy1 wx1 c1 c2
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c1: commit;
+step c2: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy2 wy2 rxy1 wx1 c2 c1
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c2: commit;
+step c1: commit;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+
+starting permutation: rxy2 wy2 rxy1 c2 wx1 c1
+step rxy2: select count(*) from gin_tbl where p @> array[5,6];
+count          
+
+10000          
+step wy2: insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g;
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step c2: commit;
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+step c1: commit;
+
+starting permutation: rxy3 wx3 rxy4 c1 wy4 c2
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step c1: commit;
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c2: commit;
+
+starting permutation: rxy3 wx3 rxy4 wy4 c1 c2
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c1: commit;
+step c2: commit;
+
+starting permutation: rxy3 wx3 rxy4 wy4 c2 c1
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c2: commit;
+step c1: commit;
+
+starting permutation: rxy3 rxy4 wx3 c1 wy4 c2
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c1: commit;
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c2: commit;
+
+starting permutation: rxy3 rxy4 wx3 wy4 c1 c2
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c1: commit;
+step c2: commit;
+
+starting permutation: rxy3 rxy4 wx3 wy4 c2 c1
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c2: commit;
+step c1: commit;
+
+starting permutation: rxy3 rxy4 wy4 wx3 c1 c2
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c1: commit;
+step c2: commit;
+
+starting permutation: rxy3 rxy4 wy4 wx3 c2 c1
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c2: commit;
+step c1: commit;
+
+starting permutation: rxy3 rxy4 wy4 c2 wx3 c1
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c2: commit;
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c1: commit;
+
+starting permutation: rxy4 rxy3 wx3 c1 wy4 c2
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c1: commit;
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c2: commit;
+
+starting permutation: rxy4 rxy3 wx3 wy4 c1 c2
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c1: commit;
+step c2: commit;
+
+starting permutation: rxy4 rxy3 wx3 wy4 c2 c1
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c2: commit;
+step c1: commit;
+
+starting permutation: rxy4 rxy3 wy4 wx3 c1 c2
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c1: commit;
+step c2: commit;
+
+starting permutation: rxy4 rxy3 wy4 wx3 c2 c1
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c2: commit;
+step c1: commit;
+
+starting permutation: rxy4 rxy3 wy4 c2 wx3 c1
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step c2: commit;
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c1: commit;
+
+starting permutation: rxy4 wy4 rxy3 wx3 c1 c2
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c1: commit;
+step c2: commit;
+
+starting permutation: rxy4 wy4 rxy3 wx3 c2 c1
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c2: commit;
+step c1: commit;
+
+starting permutation: rxy4 wy4 rxy3 c2 wx3 c1
+step rxy4: select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000];
+count          
+
+4              
+step wy4: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g;
+step rxy3: select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000];
+count          
+
+4              
+step c2: commit;
+step wx3: insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g;
+step c1: commit;
+
+starting permutation: rxy1 rxy2fu wx1 c1 wy2fu c2
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step rxy2fu: select count(*) from gin_tbl where p @> array[10000,10005];
+count          
+
+0              
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c1: commit;
+step wy2fu: insert into gin_tbl select g, array[10000,10005] from
+              generate_series(20051, 20100) g;
+step c2: commit;
+
+starting permutation: fu1 rxy1 rxy2fu wx1 c1 wy2fu c2
+step fu1: alter index ginidx set (fastupdate = on);
+			  commit;
+			  begin isolation level serializable; 
+  			  set enable_seqscan=off;
+step rxy1: select count(*) from gin_tbl where p @> array[4,5];
+count          
+
+10000          
+step rxy2fu: select count(*) from gin_tbl where p @> array[10000,10005];
+count          
+
+0              
+step wx1: insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g;
+step c1: commit;
+step wy2fu: insert into gin_tbl select g, array[10000,10005] from
+              generate_series(20051, 20100) g;
+ERROR:  could not serialize access due to read/write dependencies among transactions
+step c2: commit;
diff --git a/src/test/isolation/isolation_schedule b/src/test/isolation/isolation_schedule
index 53e1f192b0b..d3965fe73f7 100644
--- a/src/test/isolation/isolation_schedule
+++ b/src/test/isolation/isolation_schedule
@@ -67,3 +67,4 @@ test: vacuum-reltuples
 test: timeouts
 test: vacuum-concurrent-drop
 test: predicate-gist
+test: predicate-gin
diff --git a/src/test/isolation/specs/predicate-gin.spec b/src/test/isolation/specs/predicate-gin.spec
new file mode 100644
index 00000000000..9f0cda80573
--- /dev/null
+++ b/src/test/isolation/specs/predicate-gin.spec
@@ -0,0 +1,134 @@
+# Test for page level predicate locking in gin index
+#
+# Test to verify serialization failures and to check reduced false positives
+#
+# To verify serialization failures, queries and permutations are written in such
+# a way that an index scan  (from one transaction) and an index insert (from
+# another transaction) will try to access the same part (sub-tree) of the index
+# whereas to check reduced false positives, they will try to access different
+# parts (sub-tree) of the index.
+
+
+setup
+{
+  create table gin_tbl(id int4, p int4[]);
+  insert into gin_tbl select g, array[g, g*2,g*3] from generate_series(1, 10000) g;
+  insert into gin_tbl select g, array[4,5,6] from generate_series(10001, 20000) g;
+  create index ginidx on gin_tbl using gin(p) with (fastupdate = off);
+}
+
+teardown
+{
+  drop table gin_tbl;
+}
+
+session "s1"
+setup
+{
+  begin isolation level serializable;
+  set enable_seqscan=off;
+}
+
+# enable pending list for a small subset of tests
+step "fu1"	{ alter index ginidx set (fastupdate = on);
+			  commit;
+			  begin isolation level serializable; 
+  			  set enable_seqscan=off; }
+
+step "rxy1"	{ select count(*) from gin_tbl where p @> array[4,5]; }
+step "wx1"	{ insert into gin_tbl select g, array[5,6] from generate_series
+              (20001, 20050) g; }
+step "rxy3"	{ select count(*) from gin_tbl where p @> array[1,2] or
+              p @> array[100,200] or p @> array[500,1000] or p @> array[1000,2000]; }
+step "wx3"	{ insert into gin_tbl select g, array[g,g*2] from generate_series
+              (1, 50) g; }
+step "c1"  { commit; }
+
+session "s2"
+setup
+{
+  begin isolation level serializable;
+  set enable_seqscan=off;
+}
+
+step "rxy2"	{ select count(*) from gin_tbl where p @> array[5,6]; }
+step "rxy2fu"	{ select count(*) from gin_tbl where p @> array[10000,10005]; }
+step "wy2"	{ insert into gin_tbl select g, array[4,5] from
+              generate_series(20051, 20100) g; }
+step "wy2fu"	{ insert into gin_tbl select g, array[10000,10005] from
+              generate_series(20051, 20100) g; }
+step "rxy4"	{ select count(*) from gin_tbl where p @> array[4000,8000] or
+              p @> array[5000,10000] or p @> array[6000,12000] or
+              p @> array[8000,16000]; }
+step "wy4"	{ insert into gin_tbl select g, array[g,g*2] from generate_series
+              (10000, 10050) g; }
+step "c2"	{ commit; }
+
+
+# An index scan (from one transaction) and an index insert (from another transaction)
+# try to access the same part of the index but one transaction commits before other
+# transaction begins so no r-w conflict.
+
+permutation "rxy1" "wx1" "c1" "rxy2" "wy2" "c2"
+permutation "rxy2" "wy2" "c2" "rxy1" "wx1" "c1"
+
+# An index scan (from one transaction) and an index insert (from another transaction)
+# try to access different parts of the index and also one transaction commits before
+# other transaction begins, so no r-w conflict.
+
+permutation "rxy3" "wx3" "c1" "rxy4" "wy4" "c2"
+permutation "rxy4" "wy4" "c2" "rxy3" "wx3" "c1"
+
+
+# An index scan (from one transaction) and an index insert (from another transaction)
+# try to access the same part of the index and one transaction begins before other
+# transaction commits so there is a r-w conflict.
+
+permutation "rxy1" "wx1" "rxy2" "c1" "wy2" "c2"
+permutation "rxy1" "wx1" "rxy2" "wy2" "c1" "c2"
+permutation "rxy1" "wx1" "rxy2" "wy2" "c2" "c1"
+permutation "rxy1" "rxy2" "wx1" "c1" "wy2" "c2"
+permutation "rxy1" "rxy2" "wx1" "wy2" "c1" "c2"
+permutation "rxy1" "rxy2" "wx1" "wy2" "c2" "c1"
+permutation "rxy1" "rxy2" "wy2" "wx1" "c1" "c2"
+permutation "rxy1" "rxy2" "wy2" "wx1" "c2" "c1"
+permutation "rxy1" "rxy2" "wy2" "c2" "wx1" "c1"
+permutation "rxy2" "rxy1" "wx1" "c1" "wy2" "c2"
+permutation "rxy2" "rxy1" "wx1" "wy2" "c1" "c2"
+permutation "rxy2" "rxy1" "wx1" "wy2" "c2" "c1"
+permutation "rxy2" "rxy1" "wy2" "wx1" "c1" "c2"
+permutation "rxy2" "rxy1" "wy2" "wx1" "c2" "c1"
+permutation "rxy2" "rxy1" "wy2" "c2" "wx1" "c1"
+permutation "rxy2" "wy2" "rxy1" "wx1" "c1" "c2"
+permutation "rxy2" "wy2" "rxy1" "wx1" "c2" "c1"
+permutation "rxy2" "wy2" "rxy1" "c2" "wx1" "c1"
+
+# An index scan (from one transaction) and an index insert (from another transaction)
+# try to access different parts of the index so no r-w conflict.
+
+permutation "rxy3" "wx3" "rxy4" "c1" "wy4" "c2"
+permutation "rxy3" "wx3" "rxy4" "wy4" "c1" "c2"
+permutation "rxy3" "wx3" "rxy4" "wy4" "c2" "c1"
+permutation "rxy3" "rxy4" "wx3" "c1" "wy4" "c2"
+permutation "rxy3" "rxy4" "wx3" "wy4" "c1" "c2"
+permutation "rxy3" "rxy4" "wx3" "wy4" "c2" "c1"
+permutation "rxy3" "rxy4" "wy4" "wx3" "c1" "c2"
+permutation "rxy3" "rxy4" "wy4" "wx3" "c2" "c1"
+permutation "rxy3" "rxy4" "wy4" "c2" "wx3" "c1"
+permutation "rxy4" "rxy3" "wx3" "c1" "wy4" "c2"
+permutation "rxy4" "rxy3" "wx3" "wy4" "c1" "c2"
+permutation "rxy4" "rxy3" "wx3" "wy4" "c2" "c1"
+permutation "rxy4" "rxy3" "wy4" "wx3" "c1" "c2"
+permutation "rxy4" "rxy3" "wy4" "wx3" "c2" "c1"
+permutation "rxy4" "rxy3" "wy4" "c2" "wx3" "c1"
+permutation "rxy4" "wy4" "rxy3" "wx3" "c1" "c2"
+permutation "rxy4" "wy4" "rxy3" "wx3" "c2" "c1"
+permutation "rxy4" "wy4" "rxy3" "c2" "wx3" "c1"
+
+# Test fastupdate = on. First test should pass because fastupdate is off and
+# sessions touches different parts of index, second should fail because
+# with fastupdate on, then whole index should be under predicate lock.
+
+permutation       "rxy1" "rxy2fu" "wx1" "c1" "wy2fu" "c2"
+permutation "fu1" "rxy1" "rxy2fu" "wx1" "c1" "wy2fu" "c2"
+