*** a/src/backend/access/gist/gist.c
--- b/src/backend/access/gist/gist.c
***************
*** 20,25 ****
--- 20,26 ----
  #include "miscadmin.h"
  #include "storage/bufmgr.h"
  #include "storage/indexfsm.h"
+ #include "storage/predicate.h"
  #include "utils/memutils.h"
  
  const XLogRecPtr XLogRecPtrForTemp = {1, 1};
***************
*** 286,291 **** gistplacetopage(GISTInsertState *state, GISTSTATE *giststate)
--- 287,294 ----
  	bool		is_splitted = false;
  	bool		is_leaf = (GistPageIsLeaf(state->stack->page)) ? true : false;
  
+ 	CheckForSerializableConflictIn(state->r, NULL, state->stack->buffer);
+ 
  	/*
  	 * if (!is_leaf) remove old key: This node's key has been modified, either
  	 * because a child split occurred or because we needed to adjust our key
*** a/src/backend/access/gist/gistget.c
--- b/src/backend/access/gist/gistget.c
***************
*** 20,25 ****
--- 20,26 ----
  #include "miscadmin.h"
  #include "pgstat.h"
  #include "storage/bufmgr.h"
+ #include "storage/predicate.h"
  #include "utils/memutils.h"
  
  
***************
*** 217,222 **** gistnext(IndexScanDesc scan, TIDBitmap *tbm)
--- 218,224 ----
  		Assert(so->curbuf != InvalidBuffer);
  		LockBuffer(so->curbuf, GIST_SHARE);
  		gistcheckpage(scan->indexRelation, so->curbuf);
+ 		PredicateLockPage(scan->indexRelation, BufferGetBlockNumber(so->curbuf));
  		p = BufferGetPage(so->curbuf);
  		opaque = GistPageGetOpaque(p);
  
*** a/src/backend/access/gist/gistvacuum.c
--- b/src/backend/access/gist/gistvacuum.c
***************
*** 23,28 ****
--- 23,29 ----
  #include "storage/freespace.h"
  #include "storage/indexfsm.h"
  #include "storage/lmgr.h"
+ #include "storage/predicate.h"
  #include "utils/memutils.h"
  
  
***************
*** 99,106 **** gistvacuumcleanup(PG_FUNCTION_ARGS)
  
  		if (PageIsNew(page) || GistPageIsDeleted(page))
  		{
! 			totFreePages++;
! 			RecordFreeIndexPage(rel, blkno);
  		}
  		else
  			lastFilledBlock = blkno;
--- 100,110 ----
  
  		if (PageIsNew(page) || GistPageIsDeleted(page))
  		{
! 			if (!PageIsPredicateLocked(rel, blkno))
! 			{
! 				totFreePages++;
! 				RecordFreeIndexPage(rel, blkno);
! 			}
  		}
  		else
  			lastFilledBlock = blkno;
*** a/src/backend/storage/lmgr/predicate.c
--- b/src/backend/storage/lmgr/predicate.c
***************
*** 87,93 ****
   *		PredicateLockShmemSize(void)
   *
   * predicate lock reporting
!  *		PredicateLockData *GetPredicateLockStatusData(void)
   *
   * predicate lock maintenance
   *		RegisterSerializableTransaction(Snapshot snapshot)
--- 87,94 ----
   *		PredicateLockShmemSize(void)
   *
   * predicate lock reporting
!  *		GetPredicateLockStatusData(void)
!  *		PageIsPredicateLocked(Relation relation, BlockNumber blkno)
   *
   * predicate lock maintenance
   *		RegisterSerializableTransaction(Snapshot snapshot)
***************
*** 727,732 **** EnsureMySerializableXidExists(void)
--- 728,771 ----
  	}
  }
  
+ /*
+  * Check whether there are any predicate locks held by any transaction
+  * for the page at the given block number.
+  *
+  * Note that the transaction may be completed but not yet subject to
+  * cleanup due to overlapping serializable transactions.  This must
+  * return valid information regardless of transaction isolation level.
+  *
+  * Also note that this doesn't check for a conflicting relation lock,
+  * just a lock specifically on the given page.
+  *
+  * One use is to support proper behavior during GiST index vacuum.
+  */
+ bool
+ PageIsPredicateLocked(const Relation relation, const BlockNumber blkno)
+ {
+ 	PREDICATELOCKTARGETTAG targettag;
+ 	uint32		targettaghash;
+ 	LWLockId	partitionLock;
+ 	PREDICATELOCKTARGET *target;
+ 
+ 	SET_PREDICATELOCKTARGETTAG_PAGE(targettag,
+ 									relation->rd_node.dbNode,
+ 									relation->rd_id,
+ 									blkno);
+ 
+ 	targettaghash = PredicateLockTargetTagHashCode(&targettag);
+ 	partitionLock = PredicateLockHashPartitionLock(targettaghash);
+ 	LWLockAcquire(partitionLock, LW_SHARED);
+ 	target = (PREDICATELOCKTARGET *)
+ 		hash_search_with_hash_value(PredicateLockTargetHash,
+ 									&targettag, targettaghash,
+ 									HASH_FIND, NULL);
+ 	LWLockRelease(partitionLock);
+ 
+ 	return (target != NULL);
+ }
+ 
  
  /*
   * Check whether a particular lock is held by this transaction.
*** a/src/include/catalog/pg_am.h
--- b/src/include/catalog/pg_am.h
***************
*** 117,123 **** DESCR("b-tree index access method");
  DATA(insert OID = 405 (  hash	1 1 f t f f f f f f f f 23 hashinsert hashbeginscan hashgettuple hashgetbitmap hashrescan hashendscan hashmarkpos hashrestrpos hashbuild hashbulkdelete hashvacuumcleanup hashcostestimate hashoptions ));
  DESCR("hash index access method");
  #define HASH_AM_OID 405
! DATA(insert OID = 783 (  gist	0 7 f f f t t t t t t f 0 gistinsert gistbeginscan gistgettuple gistgetbitmap gistrescan gistendscan gistmarkpos gistrestrpos gistbuild gistbulkdelete gistvacuumcleanup gistcostestimate gistoptions ));
  DESCR("GiST index access method");
  #define GIST_AM_OID 783
  DATA(insert OID = 2742 (  gin	0 5 f f f t t f f t f f 0 gininsert ginbeginscan - gingetbitmap ginrescan ginendscan ginmarkpos ginrestrpos ginbuild ginbulkdelete ginvacuumcleanup gincostestimate ginoptions ));
--- 117,123 ----
  DATA(insert OID = 405 (  hash	1 1 f t f f f f f f f f 23 hashinsert hashbeginscan hashgettuple hashgetbitmap hashrescan hashendscan hashmarkpos hashrestrpos hashbuild hashbulkdelete hashvacuumcleanup hashcostestimate hashoptions ));
  DESCR("hash index access method");
  #define HASH_AM_OID 405
! DATA(insert OID = 783 (  gist	0 7 f f f t t t t t t t 0 gistinsert gistbeginscan gistgettuple gistgetbitmap gistrescan gistendscan gistmarkpos gistrestrpos gistbuild gistbulkdelete gistvacuumcleanup gistcostestimate gistoptions ));
  DESCR("GiST index access method");
  #define GIST_AM_OID 783
  DATA(insert OID = 2742 (  gin	0 5 f f f t t f f t f f 0 gininsert ginbeginscan - gingetbitmap ginrescan ginendscan ginmarkpos ginrestrpos ginbuild ginbulkdelete ginvacuumcleanup gincostestimate ginoptions ));
*** a/src/include/storage/predicate.h
--- b/src/include/storage/predicate.h
***************
*** 156,161 **** extern Size PredicateLockShmemSize(void);
--- 156,162 ----
  
  /* predicate lock reporting */
  extern PredicateLockData *GetPredicateLockStatusData(void);
+ extern bool PageIsPredicateLocked(const Relation relation, const BlockNumber blkno);
  
  /* predicate lock maintenance */
  extern void RegisterSerializableTransaction(const Snapshot snapshot);