Adding upstream version 15.5.upstream/15.5

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 10097 insertions, 0 deletions

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
new file mode 100644
index 0000000..c74fbd0
--- /dev/null
+++ b/src/backend/access/heap/heapam.c
@@ -0,0 +1,10097 @@
+/*-------------------------------------------------------------------------
+ *
+ * heapam.c
+ *	  heap access method code
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/access/heap/heapam.c
+ *
+ *
+ * INTERFACE ROUTINES
+ *		heap_beginscan	- begin relation scan
+ *		heap_rescan		- restart a relation scan
+ *		heap_endscan	- end relation scan
+ *		heap_getnext	- retrieve next tuple in scan
+ *		heap_fetch		- retrieve tuple with given tid
+ *		heap_insert		- insert tuple into a relation
+ *		heap_multi_insert - insert multiple tuples into a relation
+ *		heap_delete		- delete a tuple from a relation
+ *		heap_update		- replace a tuple in a relation with another tuple
+ *
+ * NOTES
+ *	  This file contains the heap_ routines which implement
+ *	  the POSTGRES heap access method used for all POSTGRES
+ *	  relations.
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/bufmask.h"
+#include "access/genam.h"
+#include "access/heapam.h"
+#include "access/heapam_xlog.h"
+#include "access/heaptoast.h"
+#include "access/hio.h"
+#include "access/multixact.h"
+#include "access/parallel.h"
+#include "access/relscan.h"
+#include "access/subtrans.h"
+#include "access/syncscan.h"
+#include "access/sysattr.h"
+#include "access/tableam.h"
+#include "access/transam.h"
+#include "access/valid.h"
+#include "access/visibilitymap.h"
+#include "access/xact.h"
+#include "access/xlog.h"
+#include "access/xloginsert.h"
+#include "access/xlogutils.h"
+#include "catalog/catalog.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "port/atomics.h"
+#include "port/pg_bitutils.h"
+#include "storage/bufmgr.h"
+#include "storage/freespace.h"
+#include "storage/lmgr.h"
+#include "storage/predicate.h"
+#include "storage/procarray.h"
+#include "storage/smgr.h"
+#include "storage/spin.h"
+#include "storage/standby.h"
+#include "utils/datum.h"
+#include "utils/inval.h"
+#include "utils/lsyscache.h"
+#include "utils/relcache.h"
+#include "utils/snapmgr.h"
+#include "utils/spccache.h"
+
+
+static HeapTuple heap_prepare_insert(Relation relation, HeapTuple tup,
+									 TransactionId xid, CommandId cid, int options);
+static XLogRecPtr log_heap_update(Relation reln, Buffer oldbuf,
+								  Buffer newbuf, HeapTuple oldtup,
+								  HeapTuple newtup, HeapTuple old_key_tuple,
+								  bool all_visible_cleared, bool new_all_visible_cleared);
+static Bitmapset *HeapDetermineColumnsInfo(Relation relation,
+										   Bitmapset *interesting_cols,
+										   Bitmapset *external_cols,
+										   HeapTuple oldtup, HeapTuple newtup,
+										   bool *has_external);
+static bool heap_acquire_tuplock(Relation relation, ItemPointer tid,
+								 LockTupleMode mode, LockWaitPolicy wait_policy,
+								 bool *have_tuple_lock);
+static void compute_new_xmax_infomask(TransactionId xmax, uint16 old_infomask,
+									  uint16 old_infomask2, TransactionId add_to_xmax,
+									  LockTupleMode mode, bool is_update,
+									  TransactionId *result_xmax, uint16 *result_infomask,
+									  uint16 *result_infomask2);
+static TM_Result heap_lock_updated_tuple(Relation rel, HeapTuple tuple,
+										 ItemPointer ctid, TransactionId xid,
+										 LockTupleMode mode);
+static void GetMultiXactIdHintBits(MultiXactId multi, uint16 *new_infomask,
+								   uint16 *new_infomask2);
+static TransactionId MultiXactIdGetUpdateXid(TransactionId xmax,
+											 uint16 t_infomask);
+static bool DoesMultiXactIdConflict(MultiXactId multi, uint16 infomask,
+									LockTupleMode lockmode, bool *current_is_member);
+static void MultiXactIdWait(MultiXactId multi, MultiXactStatus status, uint16 infomask,
+							Relation rel, ItemPointer ctid, XLTW_Oper oper,
+							int *remaining);
+static bool ConditionalMultiXactIdWait(MultiXactId multi, MultiXactStatus status,
+									   uint16 infomask, Relation rel, int *remaining);
+static void index_delete_sort(TM_IndexDeleteOp *delstate);
+static int	bottomup_sort_and_shrink(TM_IndexDeleteOp *delstate);
+static XLogRecPtr log_heap_new_cid(Relation relation, HeapTuple tup);
+static HeapTuple ExtractReplicaIdentity(Relation rel, HeapTuple tup, bool key_required,
+										bool *copy);
+
+
+/*
+ * Each tuple lock mode has a corresponding heavyweight lock, and one or two
+ * corresponding MultiXactStatuses (one to merely lock tuples, another one to
+ * update them).  This table (and the macros below) helps us determine the
+ * heavyweight lock mode and MultiXactStatus values to use for any particular
+ * tuple lock strength.
+ *
+ * Don't look at lockstatus/updstatus directly!  Use get_mxact_status_for_lock
+ * instead.
+ */
+static const struct
+{
+	LOCKMODE	hwlock;
+	int			lockstatus;
+	int			updstatus;
+}
+
+			tupleLockExtraInfo[MaxLockTupleMode + 1] =
+{
+	{							/* LockTupleKeyShare */
+		AccessShareLock,
+		MultiXactStatusForKeyShare,
+		-1						/* KeyShare does not allow updating tuples */
+	},
+	{							/* LockTupleShare */
+		RowShareLock,
+		MultiXactStatusForShare,
+		-1						/* Share does not allow updating tuples */
+	},
+	{							/* LockTupleNoKeyExclusive */
+		ExclusiveLock,
+		MultiXactStatusForNoKeyUpdate,
+		MultiXactStatusNoKeyUpdate
+	},
+	{							/* LockTupleExclusive */
+		AccessExclusiveLock,
+		MultiXactStatusForUpdate,
+		MultiXactStatusUpdate
+	}
+};
+
+/* Get the LOCKMODE for a given MultiXactStatus */
+#define LOCKMODE_from_mxstatus(status) \
+			(tupleLockExtraInfo[TUPLOCK_from_mxstatus((status))].hwlock)
+
+/*
+ * Acquire heavyweight locks on tuples, using a LockTupleMode strength value.
+ * This is more readable than having every caller translate it to lock.h's
+ * LOCKMODE.
+ */
+#define LockTupleTuplock(rel, tup, mode) \
+	LockTuple((rel), (tup), tupleLockExtraInfo[mode].hwlock)
+#define UnlockTupleTuplock(rel, tup, mode) \
+	UnlockTuple((rel), (tup), tupleLockExtraInfo[mode].hwlock)
+#define ConditionalLockTupleTuplock(rel, tup, mode) \
+	ConditionalLockTuple((rel), (tup), tupleLockExtraInfo[mode].hwlock)
+
+#ifdef USE_PREFETCH
+/*
+ * heap_index_delete_tuples and index_delete_prefetch_buffer use this
+ * structure to coordinate prefetching activity
+ */
+typedef struct
+{
+	BlockNumber cur_hblkno;
+	int			next_item;
+	int			ndeltids;
+	TM_IndexDelete *deltids;
+} IndexDeletePrefetchState;
+#endif
+
+/* heap_index_delete_tuples bottom-up index deletion costing constants */
+#define BOTTOMUP_MAX_NBLOCKS			6
+#define BOTTOMUP_TOLERANCE_NBLOCKS		3
+
+/*
+ * heap_index_delete_tuples uses this when determining which heap blocks it
+ * must visit to help its bottom-up index deletion caller
+ */
+typedef struct IndexDeleteCounts
+{
+	int16		npromisingtids; /* Number of "promising" TIDs in group */
+	int16		ntids;			/* Number of TIDs in group */
+	int16		ifirsttid;		/* Offset to group's first deltid */
+} IndexDeleteCounts;
+
+/*
+ * This table maps tuple lock strength values for each particular
+ * MultiXactStatus value.
+ */
+static const int MultiXactStatusLock[MaxMultiXactStatus + 1] =
+{
+	LockTupleKeyShare,			/* ForKeyShare */
+	LockTupleShare,				/* ForShare */
+	LockTupleNoKeyExclusive,	/* ForNoKeyUpdate */
+	LockTupleExclusive,			/* ForUpdate */
+	LockTupleNoKeyExclusive,	/* NoKeyUpdate */
+	LockTupleExclusive			/* Update */
+};
+
+/* Get the LockTupleMode for a given MultiXactStatus */
+#define TUPLOCK_from_mxstatus(status) \
+			(MultiXactStatusLock[(status)])
+
+/* ----------------------------------------------------------------
+ *						 heap support routines
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------
+ *		initscan - scan code common to heap_beginscan and heap_rescan
+ * ----------------
+ */
+static void
+initscan(HeapScanDesc scan, ScanKey key, bool keep_startblock)
+{
+	ParallelBlockTableScanDesc bpscan = NULL;
+	bool		allow_strat;
+	bool		allow_sync;
+
+	/*
+	 * Determine the number of blocks we have to scan.
+	 *
+	 * It is sufficient to do this once at scan start, since any tuples added
+	 * while the scan is in progress will be invisible to my snapshot anyway.
+	 * (That is not true when using a non-MVCC snapshot.  However, we couldn't
+	 * guarantee to return tuples added after scan start anyway, since they
+	 * might go into pages we already scanned.  To guarantee consistent
+	 * results for a non-MVCC snapshot, the caller must hold some higher-level
+	 * lock that ensures the interesting tuple(s) won't change.)
+	 */
+	if (scan->rs_base.rs_parallel != NULL)
+	{
+		bpscan = (ParallelBlockTableScanDesc) scan->rs_base.rs_parallel;
+		scan->rs_nblocks = bpscan->phs_nblocks;
+	}
+	else
+		scan->rs_nblocks = RelationGetNumberOfBlocks(scan->rs_base.rs_rd);
+
+	/*
+	 * If the table is large relative to NBuffers, use a bulk-read access
+	 * strategy and enable synchronized scanning (see syncscan.c).  Although
+	 * the thresholds for these features could be different, we make them the
+	 * same so that there are only two behaviors to tune rather than four.
+	 * (However, some callers need to be able to disable one or both of these
+	 * behaviors, independently of the size of the table; also there is a GUC
+	 * variable that can disable synchronized scanning.)
+	 *
+	 * Note that table_block_parallelscan_initialize has a very similar test;
+	 * if you change this, consider changing that one, too.
+	 */
+	if (!RelationUsesLocalBuffers(scan->rs_base.rs_rd) &&
+		scan->rs_nblocks > NBuffers / 4)
+	{
+		allow_strat = (scan->rs_base.rs_flags & SO_ALLOW_STRAT) != 0;
+		allow_sync = (scan->rs_base.rs_flags & SO_ALLOW_SYNC) != 0;
+	}
+	else
+		allow_strat = allow_sync = false;
+
+	if (allow_strat)
+	{
+		/* During a rescan, keep the previous strategy object. */
+		if (scan->rs_strategy == NULL)
+			scan->rs_strategy = GetAccessStrategy(BAS_BULKREAD);
+	}
+	else
+	{
+		if (scan->rs_strategy != NULL)
+			FreeAccessStrategy(scan->rs_strategy);
+		scan->rs_strategy = NULL;
+	}
+
+	if (scan->rs_base.rs_parallel != NULL)
+	{
+		/* For parallel scan, believe whatever ParallelTableScanDesc says. */
+		if (scan->rs_base.rs_parallel->phs_syncscan)
+			scan->rs_base.rs_flags |= SO_ALLOW_SYNC;
+		else
+			scan->rs_base.rs_flags &= ~SO_ALLOW_SYNC;
+	}
+	else if (keep_startblock)
+	{
+		/*
+		 * When rescanning, we want to keep the previous startblock setting,
+		 * so that rewinding a cursor doesn't generate surprising results.
+		 * Reset the active syncscan setting, though.
+		 */
+		if (allow_sync && synchronize_seqscans)
+			scan->rs_base.rs_flags |= SO_ALLOW_SYNC;
+		else
+			scan->rs_base.rs_flags &= ~SO_ALLOW_SYNC;
+	}
+	else if (allow_sync && synchronize_seqscans)
+	{
+		scan->rs_base.rs_flags |= SO_ALLOW_SYNC;
+		scan->rs_startblock = ss_get_location(scan->rs_base.rs_rd, scan->rs_nblocks);
+	}
+	else
+	{
+		scan->rs_base.rs_flags &= ~SO_ALLOW_SYNC;
+		scan->rs_startblock = 0;
+	}
+
+	scan->rs_numblocks = InvalidBlockNumber;
+	scan->rs_inited = false;
+	scan->rs_ctup.t_data = NULL;
+	ItemPointerSetInvalid(&scan->rs_ctup.t_self);
+	scan->rs_cbuf = InvalidBuffer;
+	scan->rs_cblock = InvalidBlockNumber;
+
+	/* page-at-a-time fields are always invalid when not rs_inited */
+
+	/*
+	 * copy the scan key, if appropriate
+	 */
+	if (key != NULL && scan->rs_base.rs_nkeys > 0)
+		memcpy(scan->rs_base.rs_key, key, scan->rs_base.rs_nkeys * sizeof(ScanKeyData));
+
+	/*
+	 * Currently, we only have a stats counter for sequential heap scans (but
+	 * e.g for bitmap scans the underlying bitmap index scans will be counted,
+	 * and for sample scans we update stats for tuple fetches).
+	 */
+	if (scan->rs_base.rs_flags & SO_TYPE_SEQSCAN)
+		pgstat_count_heap_scan(scan->rs_base.rs_rd);
+}
+
+/*
+ * heap_setscanlimits - restrict range of a heapscan
+ *
+ * startBlk is the page to start at
+ * numBlks is number of pages to scan (InvalidBlockNumber means "all")
+ */
+void
+heap_setscanlimits(TableScanDesc sscan, BlockNumber startBlk, BlockNumber numBlks)
+{
+	HeapScanDesc scan = (HeapScanDesc) sscan;
+
+	Assert(!scan->rs_inited);	/* else too late to change */
+	/* else rs_startblock is significant */
+	Assert(!(scan->rs_base.rs_flags & SO_ALLOW_SYNC));
+
+	/* Check startBlk is valid (but allow case of zero blocks...) */
+	Assert(startBlk == 0 || startBlk < scan->rs_nblocks);
+
+	scan->rs_startblock = startBlk;
+	scan->rs_numblocks = numBlks;
+}
+
+/*
+ * heapgetpage - subroutine for heapgettup()
+ *
+ * This routine reads and pins the specified page of the relation.
+ * In page-at-a-time mode it performs additional work, namely determining
+ * which tuples on the page are visible.
+ */
+void
+heapgetpage(TableScanDesc sscan, BlockNumber page)
+{
+	HeapScanDesc scan = (HeapScanDesc) sscan;
+	Buffer		buffer;
+	Snapshot	snapshot;
+	Page		dp;
+	int			lines;
+	int			ntup;
+	OffsetNumber lineoff;
+	ItemId		lpp;
+	bool		all_visible;
+
+	Assert(page < scan->rs_nblocks);
+
+	/* release previous scan buffer, if any */
+	if (BufferIsValid(scan->rs_cbuf))
+	{
+		ReleaseBuffer(scan->rs_cbuf);
+		scan->rs_cbuf = InvalidBuffer;
+	}
+
+	/*
+	 * Be sure to check for interrupts at least once per page.  Checks at
+	 * higher code levels won't be able to stop a seqscan that encounters many
+	 * pages' worth of consecutive dead tuples.
+	 */
+	CHECK_FOR_INTERRUPTS();
+
+	/* read page using selected strategy */
+	scan->rs_cbuf = ReadBufferExtended(scan->rs_base.rs_rd, MAIN_FORKNUM, page,
+									   RBM_NORMAL, scan->rs_strategy);
+	scan->rs_cblock = page;
+
+	if (!(scan->rs_base.rs_flags & SO_ALLOW_PAGEMODE))
+		return;
+
+	buffer = scan->rs_cbuf;
+	snapshot = scan->rs_base.rs_snapshot;
+
+	/*
+	 * Prune and repair fragmentation for the whole page, if possible.
+	 */
+	heap_page_prune_opt(scan->rs_base.rs_rd, buffer);
+
+	/*
+	 * We must hold share lock on the buffer content while examining tuple
+	 * visibility.  Afterwards, however, the tuples we have found to be
+	 * visible are guaranteed good as long as we hold the buffer pin.
+	 */
+	LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+	dp = BufferGetPage(buffer);
+	TestForOldSnapshot(snapshot, scan->rs_base.rs_rd, dp);
+	lines = PageGetMaxOffsetNumber(dp);
+	ntup = 0;
+
+	/*
+	 * If the all-visible flag indicates that all tuples on the page are
+	 * visible to everyone, we can skip the per-tuple visibility tests.
+	 *
+	 * Note: In hot standby, a tuple that's already visible to all
+	 * transactions on the primary might still be invisible to a read-only
+	 * transaction in the standby. We partly handle this problem by tracking
+	 * the minimum xmin of visible tuples as the cut-off XID while marking a
+	 * page all-visible on the primary and WAL log that along with the
+	 * visibility map SET operation. In hot standby, we wait for (or abort)
+	 * all transactions that can potentially may not see one or more tuples on
+	 * the page. That's how index-only scans work fine in hot standby. A
+	 * crucial difference between index-only scans and heap scans is that the
+	 * index-only scan completely relies on the visibility map where as heap
+	 * scan looks at the page-level PD_ALL_VISIBLE flag. We are not sure if
+	 * the page-level flag can be trusted in the same way, because it might
+	 * get propagated somehow without being explicitly WAL-logged, e.g. via a
+	 * full page write. Until we can prove that beyond doubt, let's check each
+	 * tuple for visibility the hard way.
+	 */
+	all_visible = PageIsAllVisible(dp) && !snapshot->takenDuringRecovery;
+
+	for (lineoff = FirstOffsetNumber, lpp = PageGetItemId(dp, lineoff);
+		 lineoff <= lines;
+		 lineoff++, lpp++)
+	{
+		if (ItemIdIsNormal(lpp))
+		{
+			HeapTupleData loctup;
+			bool		valid;
+
+			loctup.t_tableOid = RelationGetRelid(scan->rs_base.rs_rd);
+			loctup.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp);
+			loctup.t_len = ItemIdGetLength(lpp);
+			ItemPointerSet(&(loctup.t_self), page, lineoff);
+
+			if (all_visible)
+				valid = true;
+			else
+				valid = HeapTupleSatisfiesVisibility(&loctup, snapshot, buffer);
+
+			HeapCheckForSerializableConflictOut(valid, scan->rs_base.rs_rd,
+												&loctup, buffer, snapshot);
+
+			if (valid)
+				scan->rs_vistuples[ntup++] = lineoff;
+		}
+	}
+
+	LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+
+	Assert(ntup <= MaxHeapTuplesPerPage);
+	scan->rs_ntuples = ntup;
+}
+
+/* ----------------
+ *		heapgettup - fetch next heap tuple
+ *
+ *		Initialize the scan if not already done; then advance to the next
+ *		tuple as indicated by "dir"; return the next tuple in scan->rs_ctup,
+ *		or set scan->rs_ctup.t_data = NULL if no more tuples.
+ *
+ * dir == NoMovementScanDirection means "re-fetch the tuple indicated
+ * by scan->rs_ctup".
+ *
+ * Note: the reason nkeys/key are passed separately, even though they are
+ * kept in the scan descriptor, is that the caller may not want us to check
+ * the scankeys.
+ *
+ * Note: when we fall off the end of the scan in either direction, we
+ * reset rs_inited.  This means that a further request with the same
+ * scan direction will restart the scan, which is a bit odd, but a
+ * request with the opposite scan direction will start a fresh scan
+ * in the proper direction.  The latter is required behavior for cursors,
+ * while the former case is generally undefined behavior in Postgres
+ * so we don't care too much.
+ * ----------------
+ */
+static void
+heapgettup(HeapScanDesc scan,
+		   ScanDirection dir,
+		   int nkeys,
+		   ScanKey key)
+{
+	HeapTuple	tuple = &(scan->rs_ctup);
+	Snapshot	snapshot = scan->rs_base.rs_snapshot;
+	bool		backward = ScanDirectionIsBackward(dir);
+	BlockNumber page;
+	bool		finished;
+	Page		dp;
+	int			lines;
+	OffsetNumber lineoff;
+	int			linesleft;
+	ItemId		lpp;
+
+	/*
+	 * calculate next starting lineoff, given scan direction
+	 */
+	if (ScanDirectionIsForward(dir))
+	{
+		if (!scan->rs_inited)
+		{
+			/*
+			 * return null immediately if relation is empty
+			 */
+			if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0)
+			{
+				Assert(!BufferIsValid(scan->rs_cbuf));
+				tuple->t_data = NULL;
+				return;
+			}
+			if (scan->rs_base.rs_parallel != NULL)
+			{
+				ParallelBlockTableScanDesc pbscan =
+				(ParallelBlockTableScanDesc) scan->rs_base.rs_parallel;
+				ParallelBlockTableScanWorker pbscanwork =
+				scan->rs_parallelworkerdata;
+
+				table_block_parallelscan_startblock_init(scan->rs_base.rs_rd,
+														 pbscanwork, pbscan);
+
+				page = table_block_parallelscan_nextpage(scan->rs_base.rs_rd,
+														 pbscanwork, pbscan);
+
+				/* Other processes might have already finished the scan. */
+				if (page == InvalidBlockNumber)
+				{
+					Assert(!BufferIsValid(scan->rs_cbuf));
+					tuple->t_data = NULL;
+					return;
+				}
+			}
+			else
+				page = scan->rs_startblock; /* first page */
+			heapgetpage((TableScanDesc) scan, page);
+			lineoff = FirstOffsetNumber;	/* first offnum */
+			scan->rs_inited = true;
+		}
+		else
+		{
+			/* continue from previously returned page/tuple */
+			page = scan->rs_cblock; /* current page */
+			lineoff =			/* next offnum */
+				OffsetNumberNext(ItemPointerGetOffsetNumber(&(tuple->t_self)));
+		}
+
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+		dp = BufferGetPage(scan->rs_cbuf);
+		TestForOldSnapshot(snapshot, scan->rs_base.rs_rd, dp);
+		lines = PageGetMaxOffsetNumber(dp);
+		/* page and lineoff now reference the physically next tid */
+
+		linesleft = lines - lineoff + 1;
+	}
+	else if (backward)
+	{
+		/* backward parallel scan not supported */
+		Assert(scan->rs_base.rs_parallel == NULL);
+
+		if (!scan->rs_inited)
+		{
+			/*
+			 * return null immediately if relation is empty
+			 */
+			if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0)
+			{
+				Assert(!BufferIsValid(scan->rs_cbuf));
+				tuple->t_data = NULL;
+				return;
+			}
+
+			/*
+			 * Disable reporting to syncscan logic in a backwards scan; it's
+			 * not very likely anyone else is doing the same thing at the same
+			 * time, and much more likely that we'll just bollix things for
+			 * forward scanners.
+			 */
+			scan->rs_base.rs_flags &= ~SO_ALLOW_SYNC;
+
+			/*
+			 * Start from last page of the scan.  Ensure we take into account
+			 * rs_numblocks if it's been adjusted by heap_setscanlimits().
+			 */
+			if (scan->rs_numblocks != InvalidBlockNumber)
+				page = (scan->rs_startblock + scan->rs_numblocks - 1) % scan->rs_nblocks;
+			else if (scan->rs_startblock > 0)
+				page = scan->rs_startblock - 1;
+			else
+				page = scan->rs_nblocks - 1;
+			heapgetpage((TableScanDesc) scan, page);
+		}
+		else
+		{
+			/* continue from previously returned page/tuple */
+			page = scan->rs_cblock; /* current page */
+		}
+
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+		dp = BufferGetPage(scan->rs_cbuf);
+		TestForOldSnapshot(snapshot, scan->rs_base.rs_rd, dp);
+		lines = PageGetMaxOffsetNumber(dp);
+
+		if (!scan->rs_inited)
+		{
+			lineoff = lines;	/* final offnum */
+			scan->rs_inited = true;
+		}
+		else
+		{
+			/*
+			 * The previous returned tuple may have been vacuumed since the
+			 * previous scan when we use a non-MVCC snapshot, so we must
+			 * re-establish the lineoff <= PageGetMaxOffsetNumber(dp)
+			 * invariant
+			 */
+			lineoff =			/* previous offnum */
+				Min(lines,
+					OffsetNumberPrev(ItemPointerGetOffsetNumber(&(tuple->t_self))));
+		}
+		/* page and lineoff now reference the physically previous tid */
+
+		linesleft = lineoff;
+	}
+	else
+	{
+		/*
+		 * ``no movement'' scan direction: refetch prior tuple
+		 */
+		if (!scan->rs_inited)
+		{
+			Assert(!BufferIsValid(scan->rs_cbuf));
+			tuple->t_data = NULL;
+			return;
+		}
+
+		page = ItemPointerGetBlockNumber(&(tuple->t_self));
+		if (page != scan->rs_cblock)
+			heapgetpage((TableScanDesc) scan, page);
+
+		/* Since the tuple was previously fetched, needn't lock page here */
+		dp = BufferGetPage(scan->rs_cbuf);
+		TestForOldSnapshot(snapshot, scan->rs_base.rs_rd, dp);
+		lineoff = ItemPointerGetOffsetNumber(&(tuple->t_self));
+		lpp = PageGetItemId(dp, lineoff);
+		Assert(ItemIdIsNormal(lpp));
+
+		tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp);
+		tuple->t_len = ItemIdGetLength(lpp);
+
+		return;
+	}
+
+	/*
+	 * advance the scan until we find a qualifying tuple or run out of stuff
+	 * to scan
+	 */
+	lpp = PageGetItemId(dp, lineoff);
+	for (;;)
+	{
+		/*
+		 * Only continue scanning the page while we have lines left.
+		 *
+		 * Note that this protects us from accessing line pointers past
+		 * PageGetMaxOffsetNumber(); both for forward scans when we resume the
+		 * table scan, and for when we start scanning a new page.
+		 */
+		while (linesleft > 0)
+		{
+			if (ItemIdIsNormal(lpp))
+			{
+				bool		valid;
+
+				tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp);
+				tuple->t_len = ItemIdGetLength(lpp);
+				ItemPointerSet(&(tuple->t_self), page, lineoff);
+
+				/*
+				 * if current tuple qualifies, return it.
+				 */
+				valid = HeapTupleSatisfiesVisibility(tuple,
+													 snapshot,
+													 scan->rs_cbuf);
+
+				HeapCheckForSerializableConflictOut(valid, scan->rs_base.rs_rd,
+													tuple, scan->rs_cbuf,
+													snapshot);
+
+				if (valid && key != NULL)
+					HeapKeyTest(tuple, RelationGetDescr(scan->rs_base.rs_rd),
+								nkeys, key, valid);
+
+				if (valid)
+				{
+					LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+					return;
+				}
+			}
+
+			/*
+			 * otherwise move to the next item on the page
+			 */
+			--linesleft;
+			if (backward)
+			{
+				--lpp;			/* move back in this page's ItemId array */
+				--lineoff;
+			}
+			else
+			{
+				++lpp;			/* move forward in this page's ItemId array */
+				++lineoff;
+			}
+		}
+
+		/*
+		 * if we get here, it means we've exhausted the items on this page and
+		 * it's time to move to the next.
+		 */
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+
+		/*
+		 * advance to next/prior page and detect end of scan
+		 */
+		if (backward)
+		{
+			finished = (page == scan->rs_startblock) ||
+				(scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks == 0 : false);
+			if (page == 0)
+				page = scan->rs_nblocks;
+			page--;
+		}
+		else if (scan->rs_base.rs_parallel != NULL)
+		{
+			ParallelBlockTableScanDesc pbscan =
+			(ParallelBlockTableScanDesc) scan->rs_base.rs_parallel;
+			ParallelBlockTableScanWorker pbscanwork =
+			scan->rs_parallelworkerdata;
+
+			page = table_block_parallelscan_nextpage(scan->rs_base.rs_rd,
+													 pbscanwork, pbscan);
+			finished = (page == InvalidBlockNumber);
+		}
+		else
+		{
+			page++;
+			if (page >= scan->rs_nblocks)
+				page = 0;
+			finished = (page == scan->rs_startblock) ||
+				(scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks == 0 : false);
+
+			/*
+			 * Report our new scan position for synchronization purposes. We
+			 * don't do that when moving backwards, however. That would just
+			 * mess up any other forward-moving scanners.
+			 *
+			 * Note: we do this before checking for end of scan so that the
+			 * final state of the position hint is back at the start of the
+			 * rel.  That's not strictly necessary, but otherwise when you run
+			 * the same query multiple times the starting position would shift
+			 * a little bit backwards on every invocation, which is confusing.
+			 * We don't guarantee any specific ordering in general, though.
+			 */
+			if (scan->rs_base.rs_flags & SO_ALLOW_SYNC)
+				ss_report_location(scan->rs_base.rs_rd, page);
+		}
+
+		/*
+		 * return NULL if we've exhausted all the pages
+		 */
+		if (finished)
+		{
+			if (BufferIsValid(scan->rs_cbuf))
+				ReleaseBuffer(scan->rs_cbuf);
+			scan->rs_cbuf = InvalidBuffer;
+			scan->rs_cblock = InvalidBlockNumber;
+			tuple->t_data = NULL;
+			scan->rs_inited = false;
+			return;
+		}
+
+		heapgetpage((TableScanDesc) scan, page);
+
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+		dp = BufferGetPage(scan->rs_cbuf);
+		TestForOldSnapshot(snapshot, scan->rs_base.rs_rd, dp);
+		lines = PageGetMaxOffsetNumber((Page) dp);
+		linesleft = lines;
+		if (backward)
+		{
+			lineoff = lines;
+			lpp = PageGetItemId(dp, lines);
+		}
+		else
+		{
+			lineoff = FirstOffsetNumber;
+			lpp = PageGetItemId(dp, FirstOffsetNumber);
+		}
+	}
+}
+
+/* ----------------
+ *		heapgettup_pagemode - fetch next heap tuple in page-at-a-time mode
+ *
+ *		Same API as heapgettup, but used in page-at-a-time mode
+ *
+ * The internal logic is much the same as heapgettup's too, but there are some
+ * differences: we do not take the buffer content lock (that only needs to
+ * happen inside heapgetpage), and we iterate through just the tuples listed
+ * in rs_vistuples[] rather than all tuples on the page.  Notice that
+ * lineindex is 0-based, where the corresponding loop variable lineoff in
+ * heapgettup is 1-based.
+ * ----------------
+ */
+static void
+heapgettup_pagemode(HeapScanDesc scan,
+					ScanDirection dir,
+					int nkeys,
+					ScanKey key)
+{
+	HeapTuple	tuple = &(scan->rs_ctup);
+	bool		backward = ScanDirectionIsBackward(dir);
+	BlockNumber page;
+	bool		finished;
+	Page		dp;
+	int			lines;
+	int			lineindex;
+	OffsetNumber lineoff;
+	int			linesleft;
+	ItemId		lpp;
+
+	/*
+	 * calculate next starting lineindex, given scan direction
+	 */
+	if (ScanDirectionIsForward(dir))
+	{
+		if (!scan->rs_inited)
+		{
+			/*
+			 * return null immediately if relation is empty
+			 */
+			if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0)
+			{
+				Assert(!BufferIsValid(scan->rs_cbuf));
+				tuple->t_data = NULL;
+				return;
+			}
+			if (scan->rs_base.rs_parallel != NULL)
+			{
+				ParallelBlockTableScanDesc pbscan =
+				(ParallelBlockTableScanDesc) scan->rs_base.rs_parallel;
+				ParallelBlockTableScanWorker pbscanwork =
+				scan->rs_parallelworkerdata;
+
+				table_block_parallelscan_startblock_init(scan->rs_base.rs_rd,
+														 pbscanwork, pbscan);
+
+				page = table_block_parallelscan_nextpage(scan->rs_base.rs_rd,
+														 pbscanwork, pbscan);
+
+				/* Other processes might have already finished the scan. */
+				if (page == InvalidBlockNumber)
+				{
+					Assert(!BufferIsValid(scan->rs_cbuf));
+					tuple->t_data = NULL;
+					return;
+				}
+			}
+			else
+				page = scan->rs_startblock; /* first page */
+			heapgetpage((TableScanDesc) scan, page);
+			lineindex = 0;
+			scan->rs_inited = true;
+		}
+		else
+		{
+			/* continue from previously returned page/tuple */
+			page = scan->rs_cblock; /* current page */
+			lineindex = scan->rs_cindex + 1;
+		}
+
+		dp = BufferGetPage(scan->rs_cbuf);
+		TestForOldSnapshot(scan->rs_base.rs_snapshot, scan->rs_base.rs_rd, dp);
+		lines = scan->rs_ntuples;
+		/* page and lineindex now reference the next visible tid */
+
+		linesleft = lines - lineindex;
+	}
+	else if (backward)
+	{
+		/* backward parallel scan not supported */
+		Assert(scan->rs_base.rs_parallel == NULL);
+
+		if (!scan->rs_inited)
+		{
+			/*
+			 * return null immediately if relation is empty
+			 */
+			if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0)
+			{
+				Assert(!BufferIsValid(scan->rs_cbuf));
+				tuple->t_data = NULL;
+				return;
+			}
+
+			/*
+			 * Disable reporting to syncscan logic in a backwards scan; it's
+			 * not very likely anyone else is doing the same thing at the same
+			 * time, and much more likely that we'll just bollix things for
+			 * forward scanners.
+			 */
+			scan->rs_base.rs_flags &= ~SO_ALLOW_SYNC;
+
+			/*
+			 * Start from last page of the scan.  Ensure we take into account
+			 * rs_numblocks if it's been adjusted by heap_setscanlimits().
+			 */
+			if (scan->rs_numblocks != InvalidBlockNumber)
+				page = (scan->rs_startblock + scan->rs_numblocks - 1) % scan->rs_nblocks;
+			else if (scan->rs_startblock > 0)
+				page = scan->rs_startblock - 1;
+			else
+				page = scan->rs_nblocks - 1;
+			heapgetpage((TableScanDesc) scan, page);
+		}
+		else
+		{
+			/* continue from previously returned page/tuple */
+			page = scan->rs_cblock; /* current page */
+		}
+
+		dp = BufferGetPage(scan->rs_cbuf);
+		TestForOldSnapshot(scan->rs_base.rs_snapshot, scan->rs_base.rs_rd, dp);
+		lines = scan->rs_ntuples;
+
+		if (!scan->rs_inited)
+		{
+			lineindex = lines - 1;
+			scan->rs_inited = true;
+		}
+		else
+		{
+			lineindex = scan->rs_cindex - 1;
+		}
+		/* page and lineindex now reference the previous visible tid */
+
+		linesleft = lineindex + 1;
+	}
+	else
+	{
+		/*
+		 * ``no movement'' scan direction: refetch prior tuple
+		 */
+		if (!scan->rs_inited)
+		{
+			Assert(!BufferIsValid(scan->rs_cbuf));
+			tuple->t_data = NULL;
+			return;
+		}
+
+		page = ItemPointerGetBlockNumber(&(tuple->t_self));
+		if (page != scan->rs_cblock)
+			heapgetpage((TableScanDesc) scan, page);
+
+		/* Since the tuple was previously fetched, needn't lock page here */
+		dp = BufferGetPage(scan->rs_cbuf);
+		TestForOldSnapshot(scan->rs_base.rs_snapshot, scan->rs_base.rs_rd, dp);
+		lineoff = ItemPointerGetOffsetNumber(&(tuple->t_self));
+		lpp = PageGetItemId(dp, lineoff);
+		Assert(ItemIdIsNormal(lpp));
+
+		tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp);
+		tuple->t_len = ItemIdGetLength(lpp);
+
+		/* check that rs_cindex is in sync */
+		Assert(scan->rs_cindex < scan->rs_ntuples);
+		Assert(lineoff == scan->rs_vistuples[scan->rs_cindex]);
+
+		return;
+	}
+
+	/*
+	 * advance the scan until we find a qualifying tuple or run out of stuff
+	 * to scan
+	 */
+	for (;;)
+	{
+		while (linesleft > 0)
+		{
+			lineoff = scan->rs_vistuples[lineindex];
+			lpp = PageGetItemId(dp, lineoff);
+			Assert(ItemIdIsNormal(lpp));
+
+			tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp);
+			tuple->t_len = ItemIdGetLength(lpp);
+			ItemPointerSet(&(tuple->t_self), page, lineoff);
+
+			/*
+			 * if current tuple qualifies, return it.
+			 */
+			if (key != NULL)
+			{
+				bool		valid;
+
+				HeapKeyTest(tuple, RelationGetDescr(scan->rs_base.rs_rd),
+							nkeys, key, valid);
+				if (valid)
+				{
+					scan->rs_cindex = lineindex;
+					return;
+				}
+			}
+			else
+			{
+				scan->rs_cindex = lineindex;
+				return;
+			}
+
+			/*
+			 * otherwise move to the next item on the page
+			 */
+			--linesleft;
+			if (backward)
+				--lineindex;
+			else
+				++lineindex;
+		}
+
+		/*
+		 * if we get here, it means we've exhausted the items on this page and
+		 * it's time to move to the next.
+		 */
+		if (backward)
+		{
+			finished = (page == scan->rs_startblock) ||
+				(scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks == 0 : false);
+			if (page == 0)
+				page = scan->rs_nblocks;
+			page--;
+		}
+		else if (scan->rs_base.rs_parallel != NULL)
+		{
+			ParallelBlockTableScanDesc pbscan =
+			(ParallelBlockTableScanDesc) scan->rs_base.rs_parallel;
+			ParallelBlockTableScanWorker pbscanwork =
+			scan->rs_parallelworkerdata;
+
+			page = table_block_parallelscan_nextpage(scan->rs_base.rs_rd,
+													 pbscanwork, pbscan);
+			finished = (page == InvalidBlockNumber);
+		}
+		else
+		{
+			page++;
+			if (page >= scan->rs_nblocks)
+				page = 0;
+			finished = (page == scan->rs_startblock) ||
+				(scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks == 0 : false);
+
+			/*
+			 * Report our new scan position for synchronization purposes. We
+			 * don't do that when moving backwards, however. That would just
+			 * mess up any other forward-moving scanners.
+			 *
+			 * Note: we do this before checking for end of scan so that the
+			 * final state of the position hint is back at the start of the
+			 * rel.  That's not strictly necessary, but otherwise when you run
+			 * the same query multiple times the starting position would shift
+			 * a little bit backwards on every invocation, which is confusing.
+			 * We don't guarantee any specific ordering in general, though.
+			 */
+			if (scan->rs_base.rs_flags & SO_ALLOW_SYNC)
+				ss_report_location(scan->rs_base.rs_rd, page);
+		}
+
+		/*
+		 * return NULL if we've exhausted all the pages
+		 */
+		if (finished)
+		{
+			if (BufferIsValid(scan->rs_cbuf))
+				ReleaseBuffer(scan->rs_cbuf);
+			scan->rs_cbuf = InvalidBuffer;
+			scan->rs_cblock = InvalidBlockNumber;
+			tuple->t_data = NULL;
+			scan->rs_inited = false;
+			return;
+		}
+
+		heapgetpage((TableScanDesc) scan, page);
+
+		dp = BufferGetPage(scan->rs_cbuf);
+		TestForOldSnapshot(scan->rs_base.rs_snapshot, scan->rs_base.rs_rd, dp);
+		lines = scan->rs_ntuples;
+		linesleft = lines;
+		if (backward)
+			lineindex = lines - 1;
+		else
+			lineindex = 0;
+	}
+}
+
+
+/* ----------------------------------------------------------------
+ *					 heap access method interface
+ * ----------------------------------------------------------------
+ */
+
+
+TableScanDesc
+heap_beginscan(Relation relation, Snapshot snapshot,
+			   int nkeys, ScanKey key,
+			   ParallelTableScanDesc parallel_scan,
+			   uint32 flags)
+{
+	HeapScanDesc scan;
+
+	/*
+	 * increment relation ref count while scanning relation
+	 *
+	 * This is just to make really sure the relcache entry won't go away while
+	 * the scan has a pointer to it.  Caller should be holding the rel open
+	 * anyway, so this is redundant in all normal scenarios...
+	 */
+	RelationIncrementReferenceCount(relation);
+
+	/*
+	 * allocate and initialize scan descriptor
+	 */
+	scan = (HeapScanDesc) palloc(sizeof(HeapScanDescData));
+
+	scan->rs_base.rs_rd = relation;
+	scan->rs_base.rs_snapshot = snapshot;
+	scan->rs_base.rs_nkeys = nkeys;
+	scan->rs_base.rs_flags = flags;
+	scan->rs_base.rs_parallel = parallel_scan;
+	scan->rs_strategy = NULL;	/* set in initscan */
+
+	/*
+	 * Disable page-at-a-time mode if it's not a MVCC-safe snapshot.
+	 */
+	if (!(snapshot && IsMVCCSnapshot(snapshot)))
+		scan->rs_base.rs_flags &= ~SO_ALLOW_PAGEMODE;
+
+	/*
+	 * For seqscan and sample scans in a serializable transaction, acquire a
+	 * predicate lock on the entire relation. This is required not only to
+	 * lock all the matching tuples, but also to conflict with new insertions
+	 * into the table. In an indexscan, we take page locks on the index pages
+	 * covering the range specified in the scan qual, but in a heap scan there
+	 * is nothing more fine-grained to lock. A bitmap scan is a different
+	 * story, there we have already scanned the index and locked the index
+	 * pages covering the predicate. But in that case we still have to lock
+	 * any matching heap tuples. For sample scan we could optimize the locking
+	 * to be at least page-level granularity, but we'd need to add per-tuple
+	 * locking for that.
+	 */
+	if (scan->rs_base.rs_flags & (SO_TYPE_SEQSCAN | SO_TYPE_SAMPLESCAN))
+	{
+		/*
+		 * Ensure a missing snapshot is noticed reliably, even if the
+		 * isolation mode means predicate locking isn't performed (and
+		 * therefore the snapshot isn't used here).
+		 */
+		Assert(snapshot);
+		PredicateLockRelation(relation, snapshot);
+	}
+
+	/* we only need to set this up once */
+	scan->rs_ctup.t_tableOid = RelationGetRelid(relation);
+
+	/*
+	 * Allocate memory to keep track of page allocation for parallel workers
+	 * when doing a parallel scan.
+	 */
+	if (parallel_scan != NULL)
+		scan->rs_parallelworkerdata = palloc(sizeof(ParallelBlockTableScanWorkerData));
+	else
+		scan->rs_parallelworkerdata = NULL;
+
+	/*
+	 * we do this here instead of in initscan() because heap_rescan also calls
+	 * initscan() and we don't want to allocate memory again
+	 */
+	if (nkeys > 0)
+		scan->rs_base.rs_key = (ScanKey) palloc(sizeof(ScanKeyData) * nkeys);
+	else
+		scan->rs_base.rs_key = NULL;
+
+	initscan(scan, key, false);
+
+	return (TableScanDesc) scan;
+}
+
+void
+heap_rescan(TableScanDesc sscan, ScanKey key, bool set_params,
+			bool allow_strat, bool allow_sync, bool allow_pagemode)
+{
+	HeapScanDesc scan = (HeapScanDesc) sscan;
+
+	if (set_params)
+	{
+		if (allow_strat)
+			scan->rs_base.rs_flags |= SO_ALLOW_STRAT;
+		else
+			scan->rs_base.rs_flags &= ~SO_ALLOW_STRAT;
+
+		if (allow_sync)
+			scan->rs_base.rs_flags |= SO_ALLOW_SYNC;
+		else
+			scan->rs_base.rs_flags &= ~SO_ALLOW_SYNC;
+
+		if (allow_pagemode && scan->rs_base.rs_snapshot &&
+			IsMVCCSnapshot(scan->rs_base.rs_snapshot))
+			scan->rs_base.rs_flags |= SO_ALLOW_PAGEMODE;
+		else
+			scan->rs_base.rs_flags &= ~SO_ALLOW_PAGEMODE;
+	}
+
+	/*
+	 * unpin scan buffers
+	 */
+	if (BufferIsValid(scan->rs_cbuf))
+		ReleaseBuffer(scan->rs_cbuf);
+
+	/*
+	 * reinitialize scan descriptor
+	 */
+	initscan(scan, key, true);
+}
+
+void
+heap_endscan(TableScanDesc sscan)
+{
+	HeapScanDesc scan = (HeapScanDesc) sscan;
+
+	/* Note: no locking manipulations needed */
+
+	/*
+	 * unpin scan buffers
+	 */
+	if (BufferIsValid(scan->rs_cbuf))
+		ReleaseBuffer(scan->rs_cbuf);
+
+	/*
+	 * decrement relation reference count and free scan descriptor storage
+	 */
+	RelationDecrementReferenceCount(scan->rs_base.rs_rd);
+
+	if (scan->rs_base.rs_key)
+		pfree(scan->rs_base.rs_key);
+
+	if (scan->rs_strategy != NULL)
+		FreeAccessStrategy(scan->rs_strategy);
+
+	if (scan->rs_parallelworkerdata != NULL)
+		pfree(scan->rs_parallelworkerdata);
+
+	if (scan->rs_base.rs_flags & SO_TEMP_SNAPSHOT)
+		UnregisterSnapshot(scan->rs_base.rs_snapshot);
+
+	pfree(scan);
+}
+
+HeapTuple
+heap_getnext(TableScanDesc sscan, ScanDirection direction)
+{
+	HeapScanDesc scan = (HeapScanDesc) sscan;
+
+	/*
+	 * This is still widely used directly, without going through table AM, so
+	 * add a safety check.  It's possible we should, at a later point,
+	 * downgrade this to an assert. The reason for checking the AM routine,
+	 * rather than the AM oid, is that this allows to write regression tests
+	 * that create another AM reusing the heap handler.
+	 */
+	if (unlikely(sscan->rs_rd->rd_tableam != GetHeapamTableAmRoutine()))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg_internal("only heap AM is supported")));
+
+	/*
+	 * We don't expect direct calls to heap_getnext with valid CheckXidAlive
+	 * for catalog or regular tables.  See detailed comments in xact.c where
+	 * these variables are declared.  Normally we have such a check at tableam
+	 * level API but this is called from many places so we need to ensure it
+	 * here.
+	 */
+	if (unlikely(TransactionIdIsValid(CheckXidAlive) && !bsysscan))
+		elog(ERROR, "unexpected heap_getnext call during logical decoding");
+
+	/* Note: no locking manipulations needed */
+
+	if (scan->rs_base.rs_flags & SO_ALLOW_PAGEMODE)
+		heapgettup_pagemode(scan, direction,
+							scan->rs_base.rs_nkeys, scan->rs_base.rs_key);
+	else
+		heapgettup(scan, direction,
+				   scan->rs_base.rs_nkeys, scan->rs_base.rs_key);
+
+	if (scan->rs_ctup.t_data == NULL)
+		return NULL;
+
+	/*
+	 * if we get here it means we have a new current scan tuple, so point to
+	 * the proper return buffer and return the tuple.
+	 */
+
+	pgstat_count_heap_getnext(scan->rs_base.rs_rd);
+
+	return &scan->rs_ctup;
+}
+
+bool
+heap_getnextslot(TableScanDesc sscan, ScanDirection direction, TupleTableSlot *slot)
+{
+	HeapScanDesc scan = (HeapScanDesc) sscan;
+
+	/* Note: no locking manipulations needed */
+
+	if (sscan->rs_flags & SO_ALLOW_PAGEMODE)
+		heapgettup_pagemode(scan, direction, sscan->rs_nkeys, sscan->rs_key);
+	else
+		heapgettup(scan, direction, sscan->rs_nkeys, sscan->rs_key);
+
+	if (scan->rs_ctup.t_data == NULL)
+	{
+		ExecClearTuple(slot);
+		return false;
+	}
+
+	/*
+	 * if we get here it means we have a new current scan tuple, so point to
+	 * the proper return buffer and return the tuple.
+	 */
+
+	pgstat_count_heap_getnext(scan->rs_base.rs_rd);
+
+	ExecStoreBufferHeapTuple(&scan->rs_ctup, slot,
+							 scan->rs_cbuf);
+	return true;
+}
+
+void
+heap_set_tidrange(TableScanDesc sscan, ItemPointer mintid,
+				  ItemPointer maxtid)
+{
+	HeapScanDesc scan = (HeapScanDesc) sscan;
+	BlockNumber startBlk;
+	BlockNumber numBlks;
+	ItemPointerData highestItem;
+	ItemPointerData lowestItem;
+
+	/*
+	 * For relations without any pages, we can simply leave the TID range
+	 * unset.  There will be no tuples to scan, therefore no tuples outside
+	 * the given TID range.
+	 */
+	if (scan->rs_nblocks == 0)
+		return;
+
+	/*
+	 * Set up some ItemPointers which point to the first and last possible
+	 * tuples in the heap.
+	 */
+	ItemPointerSet(&highestItem, scan->rs_nblocks - 1, MaxOffsetNumber);
+	ItemPointerSet(&lowestItem, 0, FirstOffsetNumber);
+
+	/*
+	 * If the given maximum TID is below the highest possible TID in the
+	 * relation, then restrict the range to that, otherwise we scan to the end
+	 * of the relation.
+	 */
+	if (ItemPointerCompare(maxtid, &highestItem) < 0)
+		ItemPointerCopy(maxtid, &highestItem);
+
+	/*
+	 * If the given minimum TID is above the lowest possible TID in the
+	 * relation, then restrict the range to only scan for TIDs above that.
+	 */
+	if (ItemPointerCompare(mintid, &lowestItem) > 0)
+		ItemPointerCopy(mintid, &lowestItem);
+
+	/*
+	 * Check for an empty range and protect from would be negative results
+	 * from the numBlks calculation below.
+	 */
+	if (ItemPointerCompare(&highestItem, &lowestItem) < 0)
+	{
+		/* Set an empty range of blocks to scan */
+		heap_setscanlimits(sscan, 0, 0);
+		return;
+	}
+
+	/*
+	 * Calculate the first block and the number of blocks we must scan. We
+	 * could be more aggressive here and perform some more validation to try
+	 * and further narrow the scope of blocks to scan by checking if the
+	 * lowerItem has an offset above MaxOffsetNumber.  In this case, we could
+	 * advance startBlk by one.  Likewise, if highestItem has an offset of 0
+	 * we could scan one fewer blocks.  However, such an optimization does not
+	 * seem worth troubling over, currently.
+	 */
+	startBlk = ItemPointerGetBlockNumberNoCheck(&lowestItem);
+
+	numBlks = ItemPointerGetBlockNumberNoCheck(&highestItem) -
+		ItemPointerGetBlockNumberNoCheck(&lowestItem) + 1;
+
+	/* Set the start block and number of blocks to scan */
+	heap_setscanlimits(sscan, startBlk, numBlks);
+
+	/* Finally, set the TID range in sscan */
+	ItemPointerCopy(&lowestItem, &sscan->rs_mintid);
+	ItemPointerCopy(&highestItem, &sscan->rs_maxtid);
+}
+
+bool
+heap_getnextslot_tidrange(TableScanDesc sscan, ScanDirection direction,
+						  TupleTableSlot *slot)
+{
+	HeapScanDesc scan = (HeapScanDesc) sscan;
+	ItemPointer mintid = &sscan->rs_mintid;
+	ItemPointer maxtid = &sscan->rs_maxtid;
+
+	/* Note: no locking manipulations needed */
+	for (;;)
+	{
+		if (sscan->rs_flags & SO_ALLOW_PAGEMODE)
+			heapgettup_pagemode(scan, direction, sscan->rs_nkeys, sscan->rs_key);
+		else
+			heapgettup(scan, direction, sscan->rs_nkeys, sscan->rs_key);
+
+		if (scan->rs_ctup.t_data == NULL)
+		{
+			ExecClearTuple(slot);
+			return false;
+		}
+
+		/*
+		 * heap_set_tidrange will have used heap_setscanlimits to limit the
+		 * range of pages we scan to only ones that can contain the TID range
+		 * we're scanning for.  Here we must filter out any tuples from these
+		 * pages that are outside of that range.
+		 */
+		if (ItemPointerCompare(&scan->rs_ctup.t_self, mintid) < 0)
+		{
+			ExecClearTuple(slot);
+
+			/*
+			 * When scanning backwards, the TIDs will be in descending order.
+			 * Future tuples in this direction will be lower still, so we can
+			 * just return false to indicate there will be no more tuples.
+			 */
+			if (ScanDirectionIsBackward(direction))
+				return false;
+
+			continue;
+		}
+
+		/*
+		 * Likewise for the final page, we must filter out TIDs greater than
+		 * maxtid.
+		 */
+		if (ItemPointerCompare(&scan->rs_ctup.t_self, maxtid) > 0)
+		{
+			ExecClearTuple(slot);
+
+			/*
+			 * When scanning forward, the TIDs will be in ascending order.
+			 * Future tuples in this direction will be higher still, so we can
+			 * just return false to indicate there will be no more tuples.
+			 */
+			if (ScanDirectionIsForward(direction))
+				return false;
+			continue;
+		}
+
+		break;
+	}
+
+	/*
+	 * if we get here it means we have a new current scan tuple, so point to
+	 * the proper return buffer and return the tuple.
+	 */
+	pgstat_count_heap_getnext(scan->rs_base.rs_rd);
+
+	ExecStoreBufferHeapTuple(&scan->rs_ctup, slot, scan->rs_cbuf);
+	return true;
+}
+
+/*
+ *	heap_fetch		- retrieve tuple with given tid
+ *
+ * On entry, tuple->t_self is the TID to fetch.  We pin the buffer holding
+ * the tuple, fill in the remaining fields of *tuple, and check the tuple
+ * against the specified snapshot.
+ *
+ * If successful (tuple found and passes snapshot time qual), then *userbuf
+ * is set to the buffer holding the tuple and true is returned.  The caller
+ * must unpin the buffer when done with the tuple.
+ *
+ * If the tuple is not found (ie, item number references a deleted slot),
+ * then tuple->t_data is set to NULL, *userbuf is set to InvalidBuffer,
+ * and false is returned.
+ *
+ * If the tuple is found but fails the time qual check, then the behavior
+ * depends on the keep_buf parameter.  If keep_buf is false, the results
+ * are the same as for the tuple-not-found case.  If keep_buf is true,
+ * then tuple->t_data and *userbuf are returned as for the success case,
+ * and again the caller must unpin the buffer; but false is returned.
+ *
+ * heap_fetch does not follow HOT chains: only the exact TID requested will
+ * be fetched.
+ *
+ * It is somewhat inconsistent that we ereport() on invalid block number but
+ * return false on invalid item number.  There are a couple of reasons though.
+ * One is that the caller can relatively easily check the block number for
+ * validity, but cannot check the item number without reading the page
+ * himself.  Another is that when we are following a t_ctid link, we can be
+ * reasonably confident that the page number is valid (since VACUUM shouldn't
+ * truncate off the destination page without having killed the referencing
+ * tuple first), but the item number might well not be good.
+ */
+bool
+heap_fetch(Relation relation,
+		   Snapshot snapshot,
+		   HeapTuple tuple,
+		   Buffer *userbuf,
+		   bool keep_buf)
+{
+	ItemPointer tid = &(tuple->t_self);
+	ItemId		lp;
+	Buffer		buffer;
+	Page		page;
+	OffsetNumber offnum;
+	bool		valid;
+
+	/*
+	 * Fetch and pin the appropriate page of the relation.
+	 */
+	buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));
+
+	/*
+	 * Need share lock on buffer to examine tuple commit status.
+	 */
+	LockBuffer(buffer, BUFFER_LOCK_SHARE);
+	page = BufferGetPage(buffer);
+	TestForOldSnapshot(snapshot, relation, page);
+
+	/*
+	 * We'd better check for out-of-range offnum in case of VACUUM since the
+	 * TID was obtained.
+	 */
+	offnum = ItemPointerGetOffsetNumber(tid);
+	if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(page))
+	{
+		LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+		ReleaseBuffer(buffer);
+		*userbuf = InvalidBuffer;
+		tuple->t_data = NULL;
+		return false;
+	}
+
+	/*
+	 * get the item line pointer corresponding to the requested tid
+	 */
+	lp = PageGetItemId(page, offnum);
+
+	/*
+	 * Must check for deleted tuple.
+	 */
+	if (!ItemIdIsNormal(lp))
+	{
+		LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+		ReleaseBuffer(buffer);
+		*userbuf = InvalidBuffer;
+		tuple->t_data = NULL;
+		return false;
+	}
+
+	/*
+	 * fill in *tuple fields
+	 */
+	tuple->t_data = (HeapTupleHeader) PageGetItem(page, lp);
+	tuple->t_len = ItemIdGetLength(lp);
+	tuple->t_tableOid = RelationGetRelid(relation);
+
+	/*
+	 * check tuple visibility, then release lock
+	 */
+	valid = HeapTupleSatisfiesVisibility(tuple, snapshot, buffer);
+
+	if (valid)
+		PredicateLockTID(relation, &(tuple->t_self), snapshot,
+						 HeapTupleHeaderGetXmin(tuple->t_data));
+
+	HeapCheckForSerializableConflictOut(valid, relation, tuple, buffer, snapshot);
+
+	LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+
+	if (valid)
+	{
+		/*
+		 * All checks passed, so return the tuple as valid. Caller is now
+		 * responsible for releasing the buffer.
+		 */
+		*userbuf = buffer;
+
+		return true;
+	}
+
+	/* Tuple failed time qual, but maybe caller wants to see it anyway. */
+	if (keep_buf)
+		*userbuf = buffer;
+	else
+	{
+		ReleaseBuffer(buffer);
+		*userbuf = InvalidBuffer;
+		tuple->t_data = NULL;
+	}
+
+	return false;
+}
+
+/*
+ *	heap_hot_search_buffer	- search HOT chain for tuple satisfying snapshot
+ *
+ * On entry, *tid is the TID of a tuple (either a simple tuple, or the root
+ * of a HOT chain), and buffer is the buffer holding this tuple.  We search
+ * for the first chain member satisfying the given snapshot.  If one is
+ * found, we update *tid to reference that tuple's offset number, and
+ * return true.  If no match, return false without modifying *tid.
+ *
+ * heapTuple is a caller-supplied buffer.  When a match is found, we return
+ * the tuple here, in addition to updating *tid.  If no match is found, the
+ * contents of this buffer on return are undefined.
+ *
+ * If all_dead is not NULL, we check non-visible tuples to see if they are
+ * globally dead; *all_dead is set true if all members of the HOT chain
+ * are vacuumable, false if not.
+ *
+ * Unlike heap_fetch, the caller must already have pin and (at least) share
+ * lock on the buffer; it is still pinned/locked at exit.
+ */
+bool
+heap_hot_search_buffer(ItemPointer tid, Relation relation, Buffer buffer,
+					   Snapshot snapshot, HeapTuple heapTuple,
+					   bool *all_dead, bool first_call)
+{
+	Page		dp = (Page) BufferGetPage(buffer);
+	TransactionId prev_xmax = InvalidTransactionId;
+	BlockNumber blkno;
+	OffsetNumber offnum;
+	bool		at_chain_start;
+	bool		valid;
+	bool		skip;
+	GlobalVisState *vistest = NULL;
+
+	/* If this is not the first call, previous call returned a (live!) tuple */
+	if (all_dead)
+		*all_dead = first_call;
+
+	blkno = ItemPointerGetBlockNumber(tid);
+	offnum = ItemPointerGetOffsetNumber(tid);
+	at_chain_start = first_call;
+	skip = !first_call;
+
+	/* XXX: we should assert that a snapshot is pushed or registered */
+	Assert(TransactionIdIsValid(RecentXmin));
+	Assert(BufferGetBlockNumber(buffer) == blkno);
+
+	/* Scan through possible multiple members of HOT-chain */
+	for (;;)
+	{
+		ItemId		lp;
+
+		/* check for bogus TID */
+		if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(dp))
+			break;
+
+		lp = PageGetItemId(dp, offnum);
+
+		/* check for unused, dead, or redirected items */
+		if (!ItemIdIsNormal(lp))
+		{
+			/* We should only see a redirect at start of chain */
+			if (ItemIdIsRedirected(lp) && at_chain_start)
+			{
+				/* Follow the redirect */
+				offnum = ItemIdGetRedirect(lp);
+				at_chain_start = false;
+				continue;
+			}
+			/* else must be end of chain */
+			break;
+		}
+
+		/*
+		 * Update heapTuple to point to the element of the HOT chain we're
+		 * currently investigating. Having t_self set correctly is important
+		 * because the SSI checks and the *Satisfies routine for historical
+		 * MVCC snapshots need the correct tid to decide about the visibility.
+		 */
+		heapTuple->t_data = (HeapTupleHeader) PageGetItem(dp, lp);
+		heapTuple->t_len = ItemIdGetLength(lp);
+		heapTuple->t_tableOid = RelationGetRelid(relation);
+		ItemPointerSet(&heapTuple->t_self, blkno, offnum);
+
+		/*
+		 * Shouldn't see a HEAP_ONLY tuple at chain start.
+		 */
+		if (at_chain_start && HeapTupleIsHeapOnly(heapTuple))
+			break;
+
+		/*
+		 * The xmin should match the previous xmax value, else chain is
+		 * broken.
+		 */
+		if (TransactionIdIsValid(prev_xmax) &&
+			!TransactionIdEquals(prev_xmax,
+								 HeapTupleHeaderGetXmin(heapTuple->t_data)))
+			break;
+
+		/*
+		 * When first_call is true (and thus, skip is initially false) we'll
+		 * return the first tuple we find.  But on later passes, heapTuple
+		 * will initially be pointing to the tuple we returned last time.
+		 * Returning it again would be incorrect (and would loop forever), so
+		 * we skip it and return the next match we find.
+		 */
+		if (!skip)
+		{
+			/* If it's visible per the snapshot, we must return it */
+			valid = HeapTupleSatisfiesVisibility(heapTuple, snapshot, buffer);
+			HeapCheckForSerializableConflictOut(valid, relation, heapTuple,
+												buffer, snapshot);
+
+			if (valid)
+			{
+				ItemPointerSetOffsetNumber(tid, offnum);
+				PredicateLockTID(relation, &heapTuple->t_self, snapshot,
+								 HeapTupleHeaderGetXmin(heapTuple->t_data));
+				if (all_dead)
+					*all_dead = false;
+				return true;
+			}
+		}
+		skip = false;
+
+		/*
+		 * If we can't see it, maybe no one else can either.  At caller
+		 * request, check whether all chain members are dead to all
+		 * transactions.
+		 *
+		 * Note: if you change the criterion here for what is "dead", fix the
+		 * planner's get_actual_variable_range() function to match.
+		 */
+		if (all_dead && *all_dead)
+		{
+			if (!vistest)
+				vistest = GlobalVisTestFor(relation);
+
+			if (!HeapTupleIsSurelyDead(heapTuple, vistest))
+				*all_dead = false;
+		}
+
+		/*
+		 * Check to see if HOT chain continues past this tuple; if so fetch
+		 * the next offnum and loop around.
+		 */
+		if (HeapTupleIsHotUpdated(heapTuple))
+		{
+			Assert(ItemPointerGetBlockNumber(&heapTuple->t_data->t_ctid) ==
+				   blkno);
+			offnum = ItemPointerGetOffsetNumber(&heapTuple->t_data->t_ctid);
+			at_chain_start = false;
+			prev_xmax = HeapTupleHeaderGetUpdateXid(heapTuple->t_data);
+		}
+		else
+			break;				/* end of chain */
+	}
+
+	return false;
+}
+
+/*
+ *	heap_get_latest_tid -  get the latest tid of a specified tuple
+ *
+ * Actually, this gets the latest version that is visible according to the
+ * scan's snapshot.  Create a scan using SnapshotDirty to get the very latest,
+ * possibly uncommitted version.
+ *
+ * *tid is both an input and an output parameter: it is updated to
+ * show the latest version of the row.  Note that it will not be changed
+ * if no version of the row passes the snapshot test.
+ */
+void
+heap_get_latest_tid(TableScanDesc sscan,
+					ItemPointer tid)
+{
+	Relation	relation = sscan->rs_rd;
+	Snapshot	snapshot = sscan->rs_snapshot;
+	ItemPointerData ctid;
+	TransactionId priorXmax;
+
+	/*
+	 * table_tuple_get_latest_tid() verified that the passed in tid is valid.
+	 * Assume that t_ctid links are valid however - there shouldn't be invalid
+	 * ones in the table.
+	 */
+	Assert(ItemPointerIsValid(tid));
+
+	/*
+	 * Loop to chase down t_ctid links.  At top of loop, ctid is the tuple we
+	 * need to examine, and *tid is the TID we will return if ctid turns out
+	 * to be bogus.
+	 *
+	 * Note that we will loop until we reach the end of the t_ctid chain.
+	 * Depending on the snapshot passed, there might be at most one visible
+	 * version of the row, but we don't try to optimize for that.
+	 */
+	ctid = *tid;
+	priorXmax = InvalidTransactionId;	/* cannot check first XMIN */
+	for (;;)
+	{
+		Buffer		buffer;
+		Page		page;
+		OffsetNumber offnum;
+		ItemId		lp;
+		HeapTupleData tp;
+		bool		valid;
+
+		/*
+		 * Read, pin, and lock the page.
+		 */
+		buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(&ctid));
+		LockBuffer(buffer, BUFFER_LOCK_SHARE);
+		page = BufferGetPage(buffer);
+		TestForOldSnapshot(snapshot, relation, page);
+
+		/*
+		 * Check for bogus item number.  This is not treated as an error
+		 * condition because it can happen while following a t_ctid link. We
+		 * just assume that the prior tid is OK and return it unchanged.
+		 */
+		offnum = ItemPointerGetOffsetNumber(&ctid);
+		if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(page))
+		{
+			UnlockReleaseBuffer(buffer);
+			break;
+		}
+		lp = PageGetItemId(page, offnum);
+		if (!ItemIdIsNormal(lp))
+		{
+			UnlockReleaseBuffer(buffer);
+			break;
+		}
+
+		/* OK to access the tuple */
+		tp.t_self = ctid;
+		tp.t_data = (HeapTupleHeader) PageGetItem(page, lp);
+		tp.t_len = ItemIdGetLength(lp);
+		tp.t_tableOid = RelationGetRelid(relation);
+
+		/*
+		 * After following a t_ctid link, we might arrive at an unrelated
+		 * tuple.  Check for XMIN match.
+		 */
+		if (TransactionIdIsValid(priorXmax) &&
+			!TransactionIdEquals(priorXmax, HeapTupleHeaderGetXmin(tp.t_data)))
+		{
+			UnlockReleaseBuffer(buffer);
+			break;
+		}
+
+		/*
+		 * Check tuple visibility; if visible, set it as the new result
+		 * candidate.
+		 */
+		valid = HeapTupleSatisfiesVisibility(&tp, snapshot, buffer);
+		HeapCheckForSerializableConflictOut(valid, relation, &tp, buffer, snapshot);
+		if (valid)
+			*tid = ctid;
+
+		/*
+		 * If there's a valid t_ctid link, follow it, else we're done.
+		 */
+		if ((tp.t_data->t_infomask & HEAP_XMAX_INVALID) ||
+			HeapTupleHeaderIsOnlyLocked(tp.t_data) ||
+			HeapTupleHeaderIndicatesMovedPartitions(tp.t_data) ||
+			ItemPointerEquals(&tp.t_self, &tp.t_data->t_ctid))
+		{
+			UnlockReleaseBuffer(buffer);
+			break;
+		}
+
+		ctid = tp.t_data->t_ctid;
+		priorXmax = HeapTupleHeaderGetUpdateXid(tp.t_data);
+		UnlockReleaseBuffer(buffer);
+	}							/* end of loop */
+}
+
+
+/*
+ * UpdateXmaxHintBits - update tuple hint bits after xmax transaction ends
+ *
+ * This is called after we have waited for the XMAX transaction to terminate.
+ * If the transaction aborted, we guarantee the XMAX_INVALID hint bit will
+ * be set on exit.  If the transaction committed, we set the XMAX_COMMITTED
+ * hint bit if possible --- but beware that that may not yet be possible,
+ * if the transaction committed asynchronously.
+ *
+ * Note that if the transaction was a locker only, we set HEAP_XMAX_INVALID
+ * even if it commits.
+ *
+ * Hence callers should look only at XMAX_INVALID.
+ *
+ * Note this is not allowed for tuples whose xmax is a multixact.
+ */
+static void
+UpdateXmaxHintBits(HeapTupleHeader tuple, Buffer buffer, TransactionId xid)
+{
+	Assert(TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple), xid));
+	Assert(!(tuple->t_infomask & HEAP_XMAX_IS_MULTI));
+
+	if (!(tuple->t_infomask & (HEAP_XMAX_COMMITTED | HEAP_XMAX_INVALID)))
+	{
+		if (!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask) &&
+			TransactionIdDidCommit(xid))
+			HeapTupleSetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
+								 xid);
+		else
+			HeapTupleSetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
+								 InvalidTransactionId);
+	}
+}
+
+
+/*
+ * GetBulkInsertState - prepare status object for a bulk insert
+ */
+BulkInsertState
+GetBulkInsertState(void)
+{
+	BulkInsertState bistate;
+
+	bistate = (BulkInsertState) palloc(sizeof(BulkInsertStateData));
+	bistate->strategy = GetAccessStrategy(BAS_BULKWRITE);
+	bistate->current_buf = InvalidBuffer;
+	return bistate;
+}
+
+/*
+ * FreeBulkInsertState - clean up after finishing a bulk insert
+ */
+void
+FreeBulkInsertState(BulkInsertState bistate)
+{
+	if (bistate->current_buf != InvalidBuffer)
+		ReleaseBuffer(bistate->current_buf);
+	FreeAccessStrategy(bistate->strategy);
+	pfree(bistate);
+}
+
+/*
+ * ReleaseBulkInsertStatePin - release a buffer currently held in bistate
+ */
+void
+ReleaseBulkInsertStatePin(BulkInsertState bistate)
+{
+	if (bistate->current_buf != InvalidBuffer)
+		ReleaseBuffer(bistate->current_buf);
+	bistate->current_buf = InvalidBuffer;
+}
+
+
+/*
+ *	heap_insert		- insert tuple into a heap
+ *
+ * The new tuple is stamped with current transaction ID and the specified
+ * command ID.
+ *
+ * See table_tuple_insert for comments about most of the input flags, except
+ * that this routine directly takes a tuple rather than a slot.
+ *
+ * There's corresponding HEAP_INSERT_ options to all the TABLE_INSERT_
+ * options, and there additionally is HEAP_INSERT_SPECULATIVE which is used to
+ * implement table_tuple_insert_speculative().
+ *
+ * On return the header fields of *tup are updated to match the stored tuple;
+ * in particular tup->t_self receives the actual TID where the tuple was
+ * stored.  But note that any toasting of fields within the tuple data is NOT
+ * reflected into *tup.
+ */
+void
+heap_insert(Relation relation, HeapTuple tup, CommandId cid,
+			int options, BulkInsertState bistate)
+{
+	TransactionId xid = GetCurrentTransactionId();
+	HeapTuple	heaptup;
+	Buffer		buffer;
+	Buffer		vmbuffer = InvalidBuffer;
+	bool		all_visible_cleared = false;
+
+	/* Cheap, simplistic check that the tuple matches the rel's rowtype. */
+	Assert(HeapTupleHeaderGetNatts(tup->t_data) <=
+		   RelationGetNumberOfAttributes(relation));
+
+	/*
+	 * Fill in tuple header fields and toast the tuple if necessary.
+	 *
+	 * Note: below this point, heaptup is the data we actually intend to store
+	 * into the relation; tup is the caller's original untoasted data.
+	 */
+	heaptup = heap_prepare_insert(relation, tup, xid, cid, options);
+
+	/*
+	 * Find buffer to insert this tuple into.  If the page is all visible,
+	 * this will also pin the requisite visibility map page.
+	 */
+	buffer = RelationGetBufferForTuple(relation, heaptup->t_len,
+									   InvalidBuffer, options, bistate,
+									   &vmbuffer, NULL);
+
+	/*
+	 * We're about to do the actual insert -- but check for conflict first, to
+	 * avoid possibly having to roll back work we've just done.
+	 *
+	 * This is safe without a recheck as long as there is no possibility of
+	 * another process scanning the page between this check and the insert
+	 * being visible to the scan (i.e., an exclusive buffer content lock is
+	 * continuously held from this point until the tuple insert is visible).
+	 *
+	 * For a heap insert, we only need to check for table-level SSI locks. Our
+	 * new tuple can't possibly conflict with existing tuple locks, and heap
+	 * page locks are only consolidated versions of tuple locks; they do not
+	 * lock "gaps" as index page locks do.  So we don't need to specify a
+	 * buffer when making the call, which makes for a faster check.
+	 */
+	CheckForSerializableConflictIn(relation, NULL, InvalidBlockNumber);
+
+	/* NO EREPORT(ERROR) from here till changes are logged */
+	START_CRIT_SECTION();
+
+	RelationPutHeapTuple(relation, buffer, heaptup,
+						 (options & HEAP_INSERT_SPECULATIVE) != 0);
+
+	if (PageIsAllVisible(BufferGetPage(buffer)))
+	{
+		all_visible_cleared = true;
+		PageClearAllVisible(BufferGetPage(buffer));
+		visibilitymap_clear(relation,
+							ItemPointerGetBlockNumber(&(heaptup->t_self)),
+							vmbuffer, VISIBILITYMAP_VALID_BITS);
+	}
+
+	/*
+	 * XXX Should we set PageSetPrunable on this page ?
+	 *
+	 * The inserting transaction may eventually abort thus making this tuple
+	 * DEAD and hence available for pruning. Though we don't want to optimize
+	 * for aborts, if no other tuple in this page is UPDATEd/DELETEd, the
+	 * aborted tuple will never be pruned until next vacuum is triggered.
+	 *
+	 * If you do add PageSetPrunable here, add it in heap_xlog_insert too.
+	 */
+
+	MarkBufferDirty(buffer);
+
+	/* XLOG stuff */
+	if (RelationNeedsWAL(relation))
+	{
+		xl_heap_insert xlrec;
+		xl_heap_header xlhdr;
+		XLogRecPtr	recptr;
+		Page		page = BufferGetPage(buffer);
+		uint8		info = XLOG_HEAP_INSERT;
+		int			bufflags = 0;
+
+		/*
+		 * If this is a catalog, we need to transmit combo CIDs to properly
+		 * decode, so log that as well.
+		 */
+		if (RelationIsAccessibleInLogicalDecoding(relation))
+			log_heap_new_cid(relation, heaptup);
+
+		/*
+		 * If this is the single and first tuple on page, we can reinit the
+		 * page instead of restoring the whole thing.  Set flag, and hide
+		 * buffer references from XLogInsert.
+		 */
+		if (ItemPointerGetOffsetNumber(&(heaptup->t_self)) == FirstOffsetNumber &&
+			PageGetMaxOffsetNumber(page) == FirstOffsetNumber)
+		{
+			info |= XLOG_HEAP_INIT_PAGE;
+			bufflags |= REGBUF_WILL_INIT;
+		}
+
+		xlrec.offnum = ItemPointerGetOffsetNumber(&heaptup->t_self);
+		xlrec.flags = 0;
+		if (all_visible_cleared)
+			xlrec.flags |= XLH_INSERT_ALL_VISIBLE_CLEARED;
+		if (options & HEAP_INSERT_SPECULATIVE)
+			xlrec.flags |= XLH_INSERT_IS_SPECULATIVE;
+		Assert(ItemPointerGetBlockNumber(&heaptup->t_self) == BufferGetBlockNumber(buffer));
+
+		/*
+		 * For logical decoding, we need the tuple even if we're doing a full
+		 * page write, so make sure it's included even if we take a full-page
+		 * image. (XXX We could alternatively store a pointer into the FPW).
+		 */
+		if (RelationIsLogicallyLogged(relation) &&
+			!(options & HEAP_INSERT_NO_LOGICAL))
+		{
+			xlrec.flags |= XLH_INSERT_CONTAINS_NEW_TUPLE;
+			bufflags |= REGBUF_KEEP_DATA;
+
+			if (IsToastRelation(relation))
+				xlrec.flags |= XLH_INSERT_ON_TOAST_RELATION;
+		}
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, SizeOfHeapInsert);
+
+		xlhdr.t_infomask2 = heaptup->t_data->t_infomask2;
+		xlhdr.t_infomask = heaptup->t_data->t_infomask;
+		xlhdr.t_hoff = heaptup->t_data->t_hoff;
+
+		/*
+		 * note we mark xlhdr as belonging to buffer; if XLogInsert decides to
+		 * write the whole page to the xlog, we don't need to store
+		 * xl_heap_header in the xlog.
+		 */
+		XLogRegisterBuffer(0, buffer, REGBUF_STANDARD | bufflags);
+		XLogRegisterBufData(0, (char *) &xlhdr, SizeOfHeapHeader);
+		/* PG73FORMAT: write bitmap [+ padding] [+ oid] + data */
+		XLogRegisterBufData(0,
+							(char *) heaptup->t_data + SizeofHeapTupleHeader,
+							heaptup->t_len - SizeofHeapTupleHeader);
+
+		/* filtering by origin on a row level is much more efficient */
+		XLogSetRecordFlags(XLOG_INCLUDE_ORIGIN);
+
+		recptr = XLogInsert(RM_HEAP_ID, info);
+
+		PageSetLSN(page, recptr);
+	}
+
+	END_CRIT_SECTION();
+
+	UnlockReleaseBuffer(buffer);
+	if (vmbuffer != InvalidBuffer)
+		ReleaseBuffer(vmbuffer);
+
+	/*
+	 * If tuple is cachable, mark it for invalidation from the caches in case
+	 * we abort.  Note it is OK to do this after releasing the buffer, because
+	 * the heaptup data structure is all in local memory, not in the shared
+	 * buffer.
+	 */
+	CacheInvalidateHeapTuple(relation, heaptup, NULL);
+
+	/* Note: speculative insertions are counted too, even if aborted later */
+	pgstat_count_heap_insert(relation, 1);
+
+	/*
+	 * If heaptup is a private copy, release it.  Don't forget to copy t_self
+	 * back to the caller's image, too.
+	 */
+	if (heaptup != tup)
+	{
+		tup->t_self = heaptup->t_self;
+		heap_freetuple(heaptup);
+	}
+}
+
+/*
+ * Subroutine for heap_insert(). Prepares a tuple for insertion. This sets the
+ * tuple header fields and toasts the tuple if necessary.  Returns a toasted
+ * version of the tuple if it was toasted, or the original tuple if not. Note
+ * that in any case, the header fields are also set in the original tuple.
+ */
+static HeapTuple
+heap_prepare_insert(Relation relation, HeapTuple tup, TransactionId xid,
+					CommandId cid, int options)
+{
+	/*
+	 * To allow parallel inserts, we need to ensure that they are safe to be
+	 * performed in workers. We have the infrastructure to allow parallel
+	 * inserts in general except for the cases where inserts generate a new
+	 * CommandId (eg. inserts into a table having a foreign key column).
+	 */
+	if (IsParallelWorker())
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
+				 errmsg("cannot insert tuples in a parallel worker")));
+
+	tup->t_data->t_infomask &= ~(HEAP_XACT_MASK);
+	tup->t_data->t_infomask2 &= ~(HEAP2_XACT_MASK);
+	tup->t_data->t_infomask |= HEAP_XMAX_INVALID;
+	HeapTupleHeaderSetXmin(tup->t_data, xid);
+	if (options & HEAP_INSERT_FROZEN)
+		HeapTupleHeaderSetXminFrozen(tup->t_data);
+
+	HeapTupleHeaderSetCmin(tup->t_data, cid);
+	HeapTupleHeaderSetXmax(tup->t_data, 0); /* for cleanliness */
+	tup->t_tableOid = RelationGetRelid(relation);
+
+	/*
+	 * If the new tuple is too big for storage or contains already toasted
+	 * out-of-line attributes from some other relation, invoke the toaster.
+	 */
+	if (relation->rd_rel->relkind != RELKIND_RELATION &&
+		relation->rd_rel->relkind != RELKIND_MATVIEW)
+	{
+		/* toast table entries should never be recursively toasted */
+		Assert(!HeapTupleHasExternal(tup));
+		return tup;
+	}
+	else if (HeapTupleHasExternal(tup) || tup->t_len > TOAST_TUPLE_THRESHOLD)
+		return heap_toast_insert_or_update(relation, tup, NULL, options);
+	else
+		return tup;
+}
+
+/*
+ *	heap_multi_insert	- insert multiple tuples into a heap
+ *
+ * This is like heap_insert(), but inserts multiple tuples in one operation.
+ * That's faster than calling heap_insert() in a loop, because when multiple
+ * tuples can be inserted on a single page, we can write just a single WAL
+ * record covering all of them, and only need to lock/unlock the page once.
+ *
+ * Note: this leaks memory into the current memory context. You can create a
+ * temporary context before calling this, if that's a problem.
+ */
+void
+heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
+				  CommandId cid, int options, BulkInsertState bistate)
+{
+	TransactionId xid = GetCurrentTransactionId();
+	HeapTuple  *heaptuples;
+	int			i;
+	int			ndone;
+	PGAlignedBlock scratch;
+	Page		page;
+	Buffer		vmbuffer = InvalidBuffer;
+	bool		needwal;
+	Size		saveFreeSpace;
+	bool		need_tuple_data = RelationIsLogicallyLogged(relation);
+	bool		need_cids = RelationIsAccessibleInLogicalDecoding(relation);
+
+	/* currently not needed (thus unsupported) for heap_multi_insert() */
+	AssertArg(!(options & HEAP_INSERT_NO_LOGICAL));
+
+	needwal = RelationNeedsWAL(relation);
+	saveFreeSpace = RelationGetTargetPageFreeSpace(relation,
+												   HEAP_DEFAULT_FILLFACTOR);
+
+	/* Toast and set header data in all the slots */
+	heaptuples = palloc(ntuples * sizeof(HeapTuple));
+	for (i = 0; i < ntuples; i++)
+	{
+		HeapTuple	tuple;
+
+		tuple = ExecFetchSlotHeapTuple(slots[i], true, NULL);
+		slots[i]->tts_tableOid = RelationGetRelid(relation);
+		tuple->t_tableOid = slots[i]->tts_tableOid;
+		heaptuples[i] = heap_prepare_insert(relation, tuple, xid, cid,
+											options);
+	}
+
+	/*
+	 * We're about to do the actual inserts -- but check for conflict first,
+	 * to minimize the possibility of having to roll back work we've just
+	 * done.
+	 *
+	 * A check here does not definitively prevent a serialization anomaly;
+	 * that check MUST be done at least past the point of acquiring an
+	 * exclusive buffer content lock on every buffer that will be affected,
+	 * and MAY be done after all inserts are reflected in the buffers and
+	 * those locks are released; otherwise there is a race condition.  Since
+	 * multiple buffers can be locked and unlocked in the loop below, and it
+	 * would not be feasible to identify and lock all of those buffers before
+	 * the loop, we must do a final check at the end.
+	 *
+	 * The check here could be omitted with no loss of correctness; it is
+	 * present strictly as an optimization.
+	 *
+	 * For heap inserts, we only need to check for table-level SSI locks. Our
+	 * new tuples can't possibly conflict with existing tuple locks, and heap
+	 * page locks are only consolidated versions of tuple locks; they do not
+	 * lock "gaps" as index page locks do.  So we don't need to specify a
+	 * buffer when making the call, which makes for a faster check.
+	 */
+	CheckForSerializableConflictIn(relation, NULL, InvalidBlockNumber);
+
+	ndone = 0;
+	while (ndone < ntuples)
+	{
+		Buffer		buffer;
+		bool		starting_with_empty_page;
+		bool		all_visible_cleared = false;
+		bool		all_frozen_set = false;
+		int			nthispage;
+
+		CHECK_FOR_INTERRUPTS();
+
+		/*
+		 * Find buffer where at least the next tuple will fit.  If the page is
+		 * all-visible, this will also pin the requisite visibility map page.
+		 *
+		 * Also pin visibility map page if COPY FREEZE inserts tuples into an
+		 * empty page. See all_frozen_set below.
+		 */
+		buffer = RelationGetBufferForTuple(relation, heaptuples[ndone]->t_len,
+										   InvalidBuffer, options, bistate,
+										   &vmbuffer, NULL);
+		page = BufferGetPage(buffer);
+
+		starting_with_empty_page = PageGetMaxOffsetNumber(page) == 0;
+
+		if (starting_with_empty_page && (options & HEAP_INSERT_FROZEN))
+			all_frozen_set = true;
+
+		/* NO EREPORT(ERROR) from here till changes are logged */
+		START_CRIT_SECTION();
+
+		/*
+		 * RelationGetBufferForTuple has ensured that the first tuple fits.
+		 * Put that on the page, and then as many other tuples as fit.
+		 */
+		RelationPutHeapTuple(relation, buffer, heaptuples[ndone], false);
+
+		/*
+		 * For logical decoding we need combo CIDs to properly decode the
+		 * catalog.
+		 */
+		if (needwal && need_cids)
+			log_heap_new_cid(relation, heaptuples[ndone]);
+
+		for (nthispage = 1; ndone + nthispage < ntuples; nthispage++)
+		{
+			HeapTuple	heaptup = heaptuples[ndone + nthispage];
+
+			if (PageGetHeapFreeSpace(page) < MAXALIGN(heaptup->t_len) + saveFreeSpace)
+				break;
+
+			RelationPutHeapTuple(relation, buffer, heaptup, false);
+
+			/*
+			 * For logical decoding we need combo CIDs to properly decode the
+			 * catalog.
+			 */
+			if (needwal && need_cids)
+				log_heap_new_cid(relation, heaptup);
+		}
+
+		/*
+		 * If the page is all visible, need to clear that, unless we're only
+		 * going to add further frozen rows to it.
+		 *
+		 * If we're only adding already frozen rows to a previously empty
+		 * page, mark it as all-visible.
+		 */
+		if (PageIsAllVisible(page) && !(options & HEAP_INSERT_FROZEN))
+		{
+			all_visible_cleared = true;
+			PageClearAllVisible(page);
+			visibilitymap_clear(relation,
+								BufferGetBlockNumber(buffer),
+								vmbuffer, VISIBILITYMAP_VALID_BITS);
+		}
+		else if (all_frozen_set)
+			PageSetAllVisible(page);
+
+		/*
+		 * XXX Should we set PageSetPrunable on this page ? See heap_insert()
+		 */
+
+		MarkBufferDirty(buffer);
+
+		/* XLOG stuff */
+		if (needwal)
+		{
+			XLogRecPtr	recptr;
+			xl_heap_multi_insert *xlrec;
+			uint8		info = XLOG_HEAP2_MULTI_INSERT;
+			char	   *tupledata;
+			int			totaldatalen;
+			char	   *scratchptr = scratch.data;
+			bool		init;
+			int			bufflags = 0;
+
+			/*
+			 * If the page was previously empty, we can reinit the page
+			 * instead of restoring the whole thing.
+			 */
+			init = starting_with_empty_page;
+
+			/* allocate xl_heap_multi_insert struct from the scratch area */
+			xlrec = (xl_heap_multi_insert *) scratchptr;
+			scratchptr += SizeOfHeapMultiInsert;
+
+			/*
+			 * Allocate offsets array. Unless we're reinitializing the page,
+			 * in that case the tuples are stored in order starting at
+			 * FirstOffsetNumber and we don't need to store the offsets
+			 * explicitly.
+			 */
+			if (!init)
+				scratchptr += nthispage * sizeof(OffsetNumber);
+
+			/* the rest of the scratch space is used for tuple data */
+			tupledata = scratchptr;
+
+			/* check that the mutually exclusive flags are not both set */
+			Assert(!(all_visible_cleared && all_frozen_set));
+
+			xlrec->flags = 0;
+			if (all_visible_cleared)
+				xlrec->flags = XLH_INSERT_ALL_VISIBLE_CLEARED;
+			if (all_frozen_set)
+				xlrec->flags = XLH_INSERT_ALL_FROZEN_SET;
+
+			xlrec->ntuples = nthispage;
+
+			/*
+			 * Write out an xl_multi_insert_tuple and the tuple data itself
+			 * for each tuple.
+			 */
+			for (i = 0; i < nthispage; i++)
+			{
+				HeapTuple	heaptup = heaptuples[ndone + i];
+				xl_multi_insert_tuple *tuphdr;
+				int			datalen;
+
+				if (!init)
+					xlrec->offsets[i] = ItemPointerGetOffsetNumber(&heaptup->t_self);
+				/* xl_multi_insert_tuple needs two-byte alignment. */
+				tuphdr = (xl_multi_insert_tuple *) SHORTALIGN(scratchptr);
+				scratchptr = ((char *) tuphdr) + SizeOfMultiInsertTuple;
+
+				tuphdr->t_infomask2 = heaptup->t_data->t_infomask2;
+				tuphdr->t_infomask = heaptup->t_data->t_infomask;
+				tuphdr->t_hoff = heaptup->t_data->t_hoff;
+
+				/* write bitmap [+ padding] [+ oid] + data */
+				datalen = heaptup->t_len - SizeofHeapTupleHeader;
+				memcpy(scratchptr,
+					   (char *) heaptup->t_data + SizeofHeapTupleHeader,
+					   datalen);
+				tuphdr->datalen = datalen;
+				scratchptr += datalen;
+			}
+			totaldatalen = scratchptr - tupledata;
+			Assert((scratchptr - scratch.data) < BLCKSZ);
+
+			if (need_tuple_data)
+				xlrec->flags |= XLH_INSERT_CONTAINS_NEW_TUPLE;
+
+			/*
+			 * Signal that this is the last xl_heap_multi_insert record
+			 * emitted by this call to heap_multi_insert(). Needed for logical
+			 * decoding so it knows when to cleanup temporary data.
+			 */
+			if (ndone + nthispage == ntuples)
+				xlrec->flags |= XLH_INSERT_LAST_IN_MULTI;
+
+			if (init)
+			{
+				info |= XLOG_HEAP_INIT_PAGE;
+				bufflags |= REGBUF_WILL_INIT;
+			}
+
+			/*
+			 * If we're doing logical decoding, include the new tuple data
+			 * even if we take a full-page image of the page.
+			 */
+			if (need_tuple_data)
+				bufflags |= REGBUF_KEEP_DATA;
+
+			XLogBeginInsert();
+			XLogRegisterData((char *) xlrec, tupledata - scratch.data);
+			XLogRegisterBuffer(0, buffer, REGBUF_STANDARD | bufflags);
+
+			XLogRegisterBufData(0, tupledata, totaldatalen);
+
+			/* filtering by origin on a row level is much more efficient */
+			XLogSetRecordFlags(XLOG_INCLUDE_ORIGIN);
+
+			recptr = XLogInsert(RM_HEAP2_ID, info);
+
+			PageSetLSN(page, recptr);
+		}
+
+		END_CRIT_SECTION();
+
+		/*
+		 * If we've frozen everything on the page, update the visibilitymap.
+		 * We're already holding pin on the vmbuffer.
+		 */
+		if (all_frozen_set)
+		{
+			Assert(PageIsAllVisible(page));
+			Assert(visibilitymap_pin_ok(BufferGetBlockNumber(buffer), vmbuffer));
+
+			/*
+			 * It's fine to use InvalidTransactionId here - this is only used
+			 * when HEAP_INSERT_FROZEN is specified, which intentionally
+			 * violates visibility rules.
+			 */
+			visibilitymap_set(relation, BufferGetBlockNumber(buffer), buffer,
+							  InvalidXLogRecPtr, vmbuffer,
+							  InvalidTransactionId,
+							  VISIBILITYMAP_ALL_VISIBLE | VISIBILITYMAP_ALL_FROZEN);
+		}
+
+		UnlockReleaseBuffer(buffer);
+		ndone += nthispage;
+
+		/*
+		 * NB: Only release vmbuffer after inserting all tuples - it's fairly
+		 * likely that we'll insert into subsequent heap pages that are likely
+		 * to use the same vm page.
+		 */
+	}
+
+	/* We're done with inserting all tuples, so release the last vmbuffer. */
+	if (vmbuffer != InvalidBuffer)
+		ReleaseBuffer(vmbuffer);
+
+	/*
+	 * We're done with the actual inserts.  Check for conflicts again, to
+	 * ensure that all rw-conflicts in to these inserts are detected.  Without
+	 * this final check, a sequential scan of the heap may have locked the
+	 * table after the "before" check, missing one opportunity to detect the
+	 * conflict, and then scanned the table before the new tuples were there,
+	 * missing the other chance to detect the conflict.
+	 *
+	 * For heap inserts, we only need to check for table-level SSI locks. Our
+	 * new tuples can't possibly conflict with existing tuple locks, and heap
+	 * page locks are only consolidated versions of tuple locks; they do not
+	 * lock "gaps" as index page locks do.  So we don't need to specify a
+	 * buffer when making the call.
+	 */
+	CheckForSerializableConflictIn(relation, NULL, InvalidBlockNumber);
+
+	/*
+	 * If tuples are cachable, mark them for invalidation from the caches in
+	 * case we abort.  Note it is OK to do this after releasing the buffer,
+	 * because the heaptuples data structure is all in local memory, not in
+	 * the shared buffer.
+	 */
+	if (IsCatalogRelation(relation))
+	{
+		for (i = 0; i < ntuples; i++)
+			CacheInvalidateHeapTuple(relation, heaptuples[i], NULL);
+	}
+
+	/* copy t_self fields back to the caller's slots */
+	for (i = 0; i < ntuples; i++)
+		slots[i]->tts_tid = heaptuples[i]->t_self;
+
+	pgstat_count_heap_insert(relation, ntuples);
+}
+
+/*
+ *	simple_heap_insert - insert a tuple
+ *
+ * Currently, this routine differs from heap_insert only in supplying
+ * a default command ID and not allowing access to the speedup options.
+ *
+ * This should be used rather than using heap_insert directly in most places
+ * where we are modifying system catalogs.
+ */
+void
+simple_heap_insert(Relation relation, HeapTuple tup)
+{
+	heap_insert(relation, tup, GetCurrentCommandId(true), 0, NULL);
+}
+
+/*
+ * Given infomask/infomask2, compute the bits that must be saved in the
+ * "infobits" field of xl_heap_delete, xl_heap_update, xl_heap_lock,
+ * xl_heap_lock_updated WAL records.
+ *
+ * See fix_infomask_from_infobits.
+ */
+static uint8
+compute_infobits(uint16 infomask, uint16 infomask2)
+{
+	return
+		((infomask & HEAP_XMAX_IS_MULTI) != 0 ? XLHL_XMAX_IS_MULTI : 0) |
+		((infomask & HEAP_XMAX_LOCK_ONLY) != 0 ? XLHL_XMAX_LOCK_ONLY : 0) |
+		((infomask & HEAP_XMAX_EXCL_LOCK) != 0 ? XLHL_XMAX_EXCL_LOCK : 0) |
+	/* note we ignore HEAP_XMAX_SHR_LOCK here */
+		((infomask & HEAP_XMAX_KEYSHR_LOCK) != 0 ? XLHL_XMAX_KEYSHR_LOCK : 0) |
+		((infomask2 & HEAP_KEYS_UPDATED) != 0 ?
+		 XLHL_KEYS_UPDATED : 0);
+}
+
+/*
+ * Given two versions of the same t_infomask for a tuple, compare them and
+ * return whether the relevant status for a tuple Xmax has changed.  This is
+ * used after a buffer lock has been released and reacquired: we want to ensure
+ * that the tuple state continues to be the same it was when we previously
+ * examined it.
+ *
+ * Note the Xmax field itself must be compared separately.
+ */
+static inline bool
+xmax_infomask_changed(uint16 new_infomask, uint16 old_infomask)
+{
+	const uint16 interesting =
+	HEAP_XMAX_IS_MULTI | HEAP_XMAX_LOCK_ONLY | HEAP_LOCK_MASK;
+
+	if ((new_infomask & interesting) != (old_infomask & interesting))
+		return true;
+
+	return false;
+}
+
+/*
+ *	heap_delete - delete a tuple
+ *
+ * See table_tuple_delete() for an explanation of the parameters, except that
+ * this routine directly takes a tuple rather than a slot.
+ *
+ * In the failure cases, the routine fills *tmfd with the tuple's t_ctid,
+ * t_xmax (resolving a possible MultiXact, if necessary), and t_cmax (the last
+ * only for TM_SelfModified, since we cannot obtain cmax from a combo CID
+ * generated by another transaction).
+ */
+TM_Result
+heap_delete(Relation relation, ItemPointer tid,
+			CommandId cid, Snapshot crosscheck, bool wait,
+			TM_FailureData *tmfd, bool changingPart)
+{
+	TM_Result	result;
+	TransactionId xid = GetCurrentTransactionId();
+	ItemId		lp;
+	HeapTupleData tp;
+	Page		page;
+	BlockNumber block;
+	Buffer		buffer;
+	Buffer		vmbuffer = InvalidBuffer;
+	TransactionId new_xmax;
+	uint16		new_infomask,
+				new_infomask2;
+	bool		have_tuple_lock = false;
+	bool		iscombo;
+	bool		all_visible_cleared = false;
+	HeapTuple	old_key_tuple = NULL;	/* replica identity of the tuple */
+	bool		old_key_copied = false;
+
+	Assert(ItemPointerIsValid(tid));
+
+	/*
+	 * Forbid this during a parallel operation, lest it allocate a combo CID.
+	 * Other workers might need that combo CID for visibility checks, and we
+	 * have no provision for broadcasting it to them.
+	 */
+	if (IsInParallelMode())
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
+				 errmsg("cannot delete tuples during a parallel operation")));
+
+	block = ItemPointerGetBlockNumber(tid);
+	buffer = ReadBuffer(relation, block);
+	page = BufferGetPage(buffer);
+
+	/*
+	 * Before locking the buffer, pin the visibility map page if it appears to
+	 * be necessary.  Since we haven't got the lock yet, someone else might be
+	 * in the middle of changing this, so we'll need to recheck after we have
+	 * the lock.
+	 */
+	if (PageIsAllVisible(page))
+		visibilitymap_pin(relation, block, &vmbuffer);
+
+	LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+
+	lp = PageGetItemId(page, ItemPointerGetOffsetNumber(tid));
+	Assert(ItemIdIsNormal(lp));
+
+	tp.t_tableOid = RelationGetRelid(relation);
+	tp.t_data = (HeapTupleHeader) PageGetItem(page, lp);
+	tp.t_len = ItemIdGetLength(lp);
+	tp.t_self = *tid;
+
+l1:
+	/*
+	 * If we didn't pin the visibility map page and the page has become all
+	 * visible while we were busy locking the buffer, we'll have to unlock and
+	 * re-lock, to avoid holding the buffer lock across an I/O.  That's a bit
+	 * unfortunate, but hopefully shouldn't happen often.
+	 */
+	if (vmbuffer == InvalidBuffer && PageIsAllVisible(page))
+	{
+		LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+		visibilitymap_pin(relation, block, &vmbuffer);
+		LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+	}
+
+	result = HeapTupleSatisfiesUpdate(&tp, cid, buffer);
+
+	if (result == TM_Invisible)
+	{
+		UnlockReleaseBuffer(buffer);
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("attempted to delete invisible tuple")));
+	}
+	else if (result == TM_BeingModified && wait)
+	{
+		TransactionId xwait;
+		uint16		infomask;
+
+		/* must copy state data before unlocking buffer */
+		xwait = HeapTupleHeaderGetRawXmax(tp.t_data);
+		infomask = tp.t_data->t_infomask;
+
+		/*
+		 * Sleep until concurrent transaction ends -- except when there's a
+		 * single locker and it's our own transaction.  Note we don't care
+		 * which lock mode the locker has, because we need the strongest one.
+		 *
+		 * Before sleeping, we need to acquire tuple lock to establish our
+		 * priority for the tuple (see heap_lock_tuple).  LockTuple will
+		 * release us when we are next-in-line for the tuple.
+		 *
+		 * If we are forced to "start over" below, we keep the tuple lock;
+		 * this arranges that we stay at the head of the line while rechecking
+		 * tuple state.
+		 */
+		if (infomask & HEAP_XMAX_IS_MULTI)
+		{
+			bool		current_is_member = false;
+
+			if (DoesMultiXactIdConflict((MultiXactId) xwait, infomask,
+										LockTupleExclusive, &current_is_member))
+			{
+				LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+
+				/*
+				 * Acquire the lock, if necessary (but skip it when we're
+				 * requesting a lock and already have one; avoids deadlock).
+				 */
+				if (!current_is_member)
+					heap_acquire_tuplock(relation, &(tp.t_self), LockTupleExclusive,
+										 LockWaitBlock, &have_tuple_lock);
+
+				/* wait for multixact */
+				MultiXactIdWait((MultiXactId) xwait, MultiXactStatusUpdate, infomask,
+								relation, &(tp.t_self), XLTW_Delete,
+								NULL);
+				LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+
+				/*
+				 * If xwait had just locked the tuple then some other xact
+				 * could update this tuple before we get to this point.  Check
+				 * for xmax change, and start over if so.
+				 *
+				 * We also must start over if we didn't pin the VM page, and
+				 * the page has become all visible.
+				 */
+				if ((vmbuffer == InvalidBuffer && PageIsAllVisible(page)) ||
+					xmax_infomask_changed(tp.t_data->t_infomask, infomask) ||
+					!TransactionIdEquals(HeapTupleHeaderGetRawXmax(tp.t_data),
+										 xwait))
+					goto l1;
+			}
+
+			/*
+			 * You might think the multixact is necessarily done here, but not
+			 * so: it could have surviving members, namely our own xact or
+			 * other subxacts of this backend.  It is legal for us to delete
+			 * the tuple in either case, however (the latter case is
+			 * essentially a situation of upgrading our former shared lock to
+			 * exclusive).  We don't bother changing the on-disk hint bits
+			 * since we are about to overwrite the xmax altogether.
+			 */
+		}
+		else if (!TransactionIdIsCurrentTransactionId(xwait))
+		{
+			/*
+			 * Wait for regular transaction to end; but first, acquire tuple
+			 * lock.
+			 */
+			LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+			heap_acquire_tuplock(relation, &(tp.t_self), LockTupleExclusive,
+								 LockWaitBlock, &have_tuple_lock);
+			XactLockTableWait(xwait, relation, &(tp.t_self), XLTW_Delete);
+			LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+
+			/*
+			 * xwait is done, but if xwait had just locked the tuple then some
+			 * other xact could update this tuple before we get to this point.
+			 * Check for xmax change, and start over if so.
+			 *
+			 * We also must start over if we didn't pin the VM page, and the
+			 * page has become all visible.
+			 */
+			if ((vmbuffer == InvalidBuffer && PageIsAllVisible(page)) ||
+				xmax_infomask_changed(tp.t_data->t_infomask, infomask) ||
+				!TransactionIdEquals(HeapTupleHeaderGetRawXmax(tp.t_data),
+									 xwait))
+				goto l1;
+
+			/* Otherwise check if it committed or aborted */
+			UpdateXmaxHintBits(tp.t_data, buffer, xwait);
+		}
+
+		/*
+		 * We may overwrite if previous xmax aborted, or if it committed but
+		 * only locked the tuple without updating it.
+		 */
+		if ((tp.t_data->t_infomask & HEAP_XMAX_INVALID) ||
+			HEAP_XMAX_IS_LOCKED_ONLY(tp.t_data->t_infomask) ||
+			HeapTupleHeaderIsOnlyLocked(tp.t_data))
+			result = TM_Ok;
+		else if (!ItemPointerEquals(&tp.t_self, &tp.t_data->t_ctid))
+			result = TM_Updated;
+		else
+			result = TM_Deleted;
+	}
+
+	if (crosscheck != InvalidSnapshot && result == TM_Ok)
+	{
+		/* Perform additional check for transaction-snapshot mode RI updates */
+		if (!HeapTupleSatisfiesVisibility(&tp, crosscheck, buffer))
+			result = TM_Updated;
+	}
+
+	if (result != TM_Ok)
+	{
+		Assert(result == TM_SelfModified ||
+			   result == TM_Updated ||
+			   result == TM_Deleted ||
+			   result == TM_BeingModified);
+		Assert(!(tp.t_data->t_infomask & HEAP_XMAX_INVALID));
+		Assert(result != TM_Updated ||
+			   !ItemPointerEquals(&tp.t_self, &tp.t_data->t_ctid));
+		tmfd->ctid = tp.t_data->t_ctid;
+		tmfd->xmax = HeapTupleHeaderGetUpdateXid(tp.t_data);
+		if (result == TM_SelfModified)
+			tmfd->cmax = HeapTupleHeaderGetCmax(tp.t_data);
+		else
+			tmfd->cmax = InvalidCommandId;
+		UnlockReleaseBuffer(buffer);
+		if (have_tuple_lock)
+			UnlockTupleTuplock(relation, &(tp.t_self), LockTupleExclusive);
+		if (vmbuffer != InvalidBuffer)
+			ReleaseBuffer(vmbuffer);
+		return result;
+	}
+
+	/*
+	 * We're about to do the actual delete -- check for conflict first, to
+	 * avoid possibly having to roll back work we've just done.
+	 *
+	 * This is safe without a recheck as long as there is no possibility of
+	 * another process scanning the page between this check and the delete
+	 * being visible to the scan (i.e., an exclusive buffer content lock is
+	 * continuously held from this point until the tuple delete is visible).
+	 */
+	CheckForSerializableConflictIn(relation, tid, BufferGetBlockNumber(buffer));
+
+	/* replace cid with a combo CID if necessary */
+	HeapTupleHeaderAdjustCmax(tp.t_data, &cid, &iscombo);
+
+	/*
+	 * Compute replica identity tuple before entering the critical section so
+	 * we don't PANIC upon a memory allocation failure.
+	 */
+	old_key_tuple = ExtractReplicaIdentity(relation, &tp, true, &old_key_copied);
+
+	/*
+	 * If this is the first possibly-multixact-able operation in the current
+	 * transaction, set my per-backend OldestMemberMXactId setting. We can be
+	 * certain that the transaction will never become a member of any older
+	 * MultiXactIds than that.  (We have to do this even if we end up just
+	 * using our own TransactionId below, since some other backend could
+	 * incorporate our XID into a MultiXact immediately afterwards.)
+	 */
+	MultiXactIdSetOldestMember();
+
+	compute_new_xmax_infomask(HeapTupleHeaderGetRawXmax(tp.t_data),
+							  tp.t_data->t_infomask, tp.t_data->t_infomask2,
+							  xid, LockTupleExclusive, true,
+							  &new_xmax, &new_infomask, &new_infomask2);
+
+	START_CRIT_SECTION();
+
+	/*
+	 * If this transaction commits, the tuple will become DEAD sooner or
+	 * later.  Set flag that this page is a candidate for pruning once our xid
+	 * falls below the OldestXmin horizon.  If the transaction finally aborts,
+	 * the subsequent page pruning will be a no-op and the hint will be
+	 * cleared.
+	 */
+	PageSetPrunable(page, xid);
+
+	if (PageIsAllVisible(page))
+	{
+		all_visible_cleared = true;
+		PageClearAllVisible(page);
+		visibilitymap_clear(relation, BufferGetBlockNumber(buffer),
+							vmbuffer, VISIBILITYMAP_VALID_BITS);
+	}
+
+	/* store transaction information of xact deleting the tuple */
+	tp.t_data->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED);
+	tp.t_data->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+	tp.t_data->t_infomask |= new_infomask;
+	tp.t_data->t_infomask2 |= new_infomask2;
+	HeapTupleHeaderClearHotUpdated(tp.t_data);
+	HeapTupleHeaderSetXmax(tp.t_data, new_xmax);
+	HeapTupleHeaderSetCmax(tp.t_data, cid, iscombo);
+	/* Make sure there is no forward chain link in t_ctid */
+	tp.t_data->t_ctid = tp.t_self;
+
+	/* Signal that this is actually a move into another partition */
+	if (changingPart)
+		HeapTupleHeaderSetMovedPartitions(tp.t_data);
+
+	MarkBufferDirty(buffer);
+
+	/*
+	 * XLOG stuff
+	 *
+	 * NB: heap_abort_speculative() uses the same xlog record and replay
+	 * routines.
+	 */
+	if (RelationNeedsWAL(relation))
+	{
+		xl_heap_delete xlrec;
+		xl_heap_header xlhdr;
+		XLogRecPtr	recptr;
+
+		/*
+		 * For logical decode we need combo CIDs to properly decode the
+		 * catalog
+		 */
+		if (RelationIsAccessibleInLogicalDecoding(relation))
+			log_heap_new_cid(relation, &tp);
+
+		xlrec.flags = 0;
+		if (all_visible_cleared)
+			xlrec.flags |= XLH_DELETE_ALL_VISIBLE_CLEARED;
+		if (changingPart)
+			xlrec.flags |= XLH_DELETE_IS_PARTITION_MOVE;
+		xlrec.infobits_set = compute_infobits(tp.t_data->t_infomask,
+											  tp.t_data->t_infomask2);
+		xlrec.offnum = ItemPointerGetOffsetNumber(&tp.t_self);
+		xlrec.xmax = new_xmax;
+
+		if (old_key_tuple != NULL)
+		{
+			if (relation->rd_rel->relreplident == REPLICA_IDENTITY_FULL)
+				xlrec.flags |= XLH_DELETE_CONTAINS_OLD_TUPLE;
+			else
+				xlrec.flags |= XLH_DELETE_CONTAINS_OLD_KEY;
+		}
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, SizeOfHeapDelete);
+
+		XLogRegisterBuffer(0, buffer, REGBUF_STANDARD);
+
+		/*
+		 * Log replica identity of the deleted tuple if there is one
+		 */
+		if (old_key_tuple != NULL)
+		{
+			xlhdr.t_infomask2 = old_key_tuple->t_data->t_infomask2;
+			xlhdr.t_infomask = old_key_tuple->t_data->t_infomask;
+			xlhdr.t_hoff = old_key_tuple->t_data->t_hoff;
+
+			XLogRegisterData((char *) &xlhdr, SizeOfHeapHeader);
+			XLogRegisterData((char *) old_key_tuple->t_data
+							 + SizeofHeapTupleHeader,
+							 old_key_tuple->t_len
+							 - SizeofHeapTupleHeader);
+		}
+
+		/* filtering by origin on a row level is much more efficient */
+		XLogSetRecordFlags(XLOG_INCLUDE_ORIGIN);
+
+		recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_DELETE);
+
+		PageSetLSN(page, recptr);
+	}
+
+	END_CRIT_SECTION();
+
+	LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+
+	if (vmbuffer != InvalidBuffer)
+		ReleaseBuffer(vmbuffer);
+
+	/*
+	 * If the tuple has toasted out-of-line attributes, we need to delete
+	 * those items too.  We have to do this before releasing the buffer
+	 * because we need to look at the contents of the tuple, but it's OK to
+	 * release the content lock on the buffer first.
+	 */
+	if (relation->rd_rel->relkind != RELKIND_RELATION &&
+		relation->rd_rel->relkind != RELKIND_MATVIEW)
+	{
+		/* toast table entries should never be recursively toasted */
+		Assert(!HeapTupleHasExternal(&tp));
+	}
+	else if (HeapTupleHasExternal(&tp))
+		heap_toast_delete(relation, &tp, false);
+
+	/*
+	 * Mark tuple for invalidation from system caches at next command
+	 * boundary. We have to do this before releasing the buffer because we
+	 * need to look at the contents of the tuple.
+	 */
+	CacheInvalidateHeapTuple(relation, &tp, NULL);
+
+	/* Now we can release the buffer */
+	ReleaseBuffer(buffer);
+
+	/*
+	 * Release the lmgr tuple lock, if we had it.
+	 */
+	if (have_tuple_lock)
+		UnlockTupleTuplock(relation, &(tp.t_self), LockTupleExclusive);
+
+	pgstat_count_heap_delete(relation);
+
+	if (old_key_tuple != NULL && old_key_copied)
+		heap_freetuple(old_key_tuple);
+
+	return TM_Ok;
+}
+
+/*
+ *	simple_heap_delete - delete a tuple
+ *
+ * This routine may be used to delete a tuple when concurrent updates of
+ * the target tuple are not expected (for example, because we have a lock
+ * on the relation associated with the tuple).  Any failure is reported
+ * via ereport().
+ */
+void
+simple_heap_delete(Relation relation, ItemPointer tid)
+{
+	TM_Result	result;
+	TM_FailureData tmfd;
+
+	result = heap_delete(relation, tid,
+						 GetCurrentCommandId(true), InvalidSnapshot,
+						 true /* wait for commit */ ,
+						 &tmfd, false /* changingPart */ );
+	switch (result)
+	{
+		case TM_SelfModified:
+			/* Tuple was already updated in current command? */
+			elog(ERROR, "tuple already updated by self");
+			break;
+
+		case TM_Ok:
+			/* done successfully */
+			break;
+
+		case TM_Updated:
+			elog(ERROR, "tuple concurrently updated");
+			break;
+
+		case TM_Deleted:
+			elog(ERROR, "tuple concurrently deleted");
+			break;
+
+		default:
+			elog(ERROR, "unrecognized heap_delete status: %u", result);
+			break;
+	}
+}
+
+/*
+ *	heap_update - replace a tuple
+ *
+ * See table_tuple_update() for an explanation of the parameters, except that
+ * this routine directly takes a tuple rather than a slot.
+ *
+ * In the failure cases, the routine fills *tmfd with the tuple's t_ctid,
+ * t_xmax (resolving a possible MultiXact, if necessary), and t_cmax (the last
+ * only for TM_SelfModified, since we cannot obtain cmax from a combo CID
+ * generated by another transaction).
+ */
+TM_Result
+heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
+			CommandId cid, Snapshot crosscheck, bool wait,
+			TM_FailureData *tmfd, LockTupleMode *lockmode)
+{
+	TM_Result	result;
+	TransactionId xid = GetCurrentTransactionId();
+	Bitmapset  *hot_attrs;
+	Bitmapset  *key_attrs;
+	Bitmapset  *id_attrs;
+	Bitmapset  *interesting_attrs;
+	Bitmapset  *modified_attrs;
+	ItemId		lp;
+	HeapTupleData oldtup;
+	HeapTuple	heaptup;
+	HeapTuple	old_key_tuple = NULL;
+	bool		old_key_copied = false;
+	Page		page;
+	BlockNumber block;
+	MultiXactStatus mxact_status;
+	Buffer		buffer,
+				newbuf,
+				vmbuffer = InvalidBuffer,
+				vmbuffer_new = InvalidBuffer;
+	bool		need_toast;
+	Size		newtupsize,
+				pagefree;
+	bool		have_tuple_lock = false;
+	bool		iscombo;
+	bool		use_hot_update = false;
+	bool		key_intact;
+	bool		all_visible_cleared = false;
+	bool		all_visible_cleared_new = false;
+	bool		checked_lockers;
+	bool		locker_remains;
+	bool		id_has_external = false;
+	TransactionId xmax_new_tuple,
+				xmax_old_tuple;
+	uint16		infomask_old_tuple,
+				infomask2_old_tuple,
+				infomask_new_tuple,
+				infomask2_new_tuple;
+
+	Assert(ItemPointerIsValid(otid));
+
+	/* Cheap, simplistic check that the tuple matches the rel's rowtype. */
+	Assert(HeapTupleHeaderGetNatts(newtup->t_data) <=
+		   RelationGetNumberOfAttributes(relation));
+
+	/*
+	 * Forbid this during a parallel operation, lest it allocate a combo CID.
+	 * Other workers might need that combo CID for visibility checks, and we
+	 * have no provision for broadcasting it to them.
+	 */
+	if (IsInParallelMode())
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
+				 errmsg("cannot update tuples during a parallel operation")));
+
+	/*
+	 * Fetch the list of attributes to be checked for various operations.
+	 *
+	 * For HOT considerations, this is wasted effort if we fail to update or
+	 * have to put the new tuple on a different page.  But we must compute the
+	 * list before obtaining buffer lock --- in the worst case, if we are
+	 * doing an update on one of the relevant system catalogs, we could
+	 * deadlock if we try to fetch the list later.  In any case, the relcache
+	 * caches the data so this is usually pretty cheap.
+	 *
+	 * We also need columns used by the replica identity and columns that are
+	 * considered the "key" of rows in the table.
+	 *
+	 * Note that we get copies of each bitmap, so we need not worry about
+	 * relcache flush happening midway through.
+	 */
+	hot_attrs = RelationGetIndexAttrBitmap(relation, INDEX_ATTR_BITMAP_ALL);
+	key_attrs = RelationGetIndexAttrBitmap(relation, INDEX_ATTR_BITMAP_KEY);
+	id_attrs = RelationGetIndexAttrBitmap(relation,
+										  INDEX_ATTR_BITMAP_IDENTITY_KEY);
+	interesting_attrs = NULL;
+	interesting_attrs = bms_add_members(interesting_attrs, hot_attrs);
+	interesting_attrs = bms_add_members(interesting_attrs, key_attrs);
+	interesting_attrs = bms_add_members(interesting_attrs, id_attrs);
+
+	block = ItemPointerGetBlockNumber(otid);
+	buffer = ReadBuffer(relation, block);
+	page = BufferGetPage(buffer);
+
+	/*
+	 * Before locking the buffer, pin the visibility map page if it appears to
+	 * be necessary.  Since we haven't got the lock yet, someone else might be
+	 * in the middle of changing this, so we'll need to recheck after we have
+	 * the lock.
+	 */
+	if (PageIsAllVisible(page))
+		visibilitymap_pin(relation, block, &vmbuffer);
+
+	LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+
+	lp = PageGetItemId(page, ItemPointerGetOffsetNumber(otid));
+	Assert(ItemIdIsNormal(lp));
+
+	/*
+	 * Fill in enough data in oldtup for HeapDetermineColumnsInfo to work
+	 * properly.
+	 */
+	oldtup.t_tableOid = RelationGetRelid(relation);
+	oldtup.t_data = (HeapTupleHeader) PageGetItem(page, lp);
+	oldtup.t_len = ItemIdGetLength(lp);
+	oldtup.t_self = *otid;
+
+	/* the new tuple is ready, except for this: */
+	newtup->t_tableOid = RelationGetRelid(relation);
+
+	/*
+	 * Determine columns modified by the update.  Additionally, identify
+	 * whether any of the unmodified replica identity key attributes in the
+	 * old tuple is externally stored or not.  This is required because for
+	 * such attributes the flattened value won't be WAL logged as part of the
+	 * new tuple so we must include it as part of the old_key_tuple.  See
+	 * ExtractReplicaIdentity.
+	 */
+	modified_attrs = HeapDetermineColumnsInfo(relation, interesting_attrs,
+											  id_attrs, &oldtup,
+											  newtup, &id_has_external);
+
+	/*
+	 * If we're not updating any "key" column, we can grab a weaker lock type.
+	 * This allows for more concurrency when we are running simultaneously
+	 * with foreign key checks.
+	 *
+	 * Note that if a column gets detoasted while executing the update, but
+	 * the value ends up being the same, this test will fail and we will use
+	 * the stronger lock.  This is acceptable; the important case to optimize
+	 * is updates that don't manipulate key columns, not those that
+	 * serendipitously arrive at the same key values.
+	 */
+	if (!bms_overlap(modified_attrs, key_attrs))
+	{
+		*lockmode = LockTupleNoKeyExclusive;
+		mxact_status = MultiXactStatusNoKeyUpdate;
+		key_intact = true;
+
+		/*
+		 * If this is the first possibly-multixact-able operation in the
+		 * current transaction, set my per-backend OldestMemberMXactId
+		 * setting. We can be certain that the transaction will never become a
+		 * member of any older MultiXactIds than that.  (We have to do this
+		 * even if we end up just using our own TransactionId below, since
+		 * some other backend could incorporate our XID into a MultiXact
+		 * immediately afterwards.)
+		 */
+		MultiXactIdSetOldestMember();
+	}
+	else
+	{
+		*lockmode = LockTupleExclusive;
+		mxact_status = MultiXactStatusUpdate;
+		key_intact = false;
+	}
+
+	/*
+	 * Note: beyond this point, use oldtup not otid to refer to old tuple.
+	 * otid may very well point at newtup->t_self, which we will overwrite
+	 * with the new tuple's location, so there's great risk of confusion if we
+	 * use otid anymore.
+	 */
+
+l2:
+	checked_lockers = false;
+	locker_remains = false;
+	result = HeapTupleSatisfiesUpdate(&oldtup, cid, buffer);
+
+	/* see below about the "no wait" case */
+	Assert(result != TM_BeingModified || wait);
+
+	if (result == TM_Invisible)
+	{
+		UnlockReleaseBuffer(buffer);
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("attempted to update invisible tuple")));
+	}
+	else if (result == TM_BeingModified && wait)
+	{
+		TransactionId xwait;
+		uint16		infomask;
+		bool		can_continue = false;
+
+		/*
+		 * XXX note that we don't consider the "no wait" case here.  This
+		 * isn't a problem currently because no caller uses that case, but it
+		 * should be fixed if such a caller is introduced.  It wasn't a
+		 * problem previously because this code would always wait, but now
+		 * that some tuple locks do not conflict with one of the lock modes we
+		 * use, it is possible that this case is interesting to handle
+		 * specially.
+		 *
+		 * This may cause failures with third-party code that calls
+		 * heap_update directly.
+		 */
+
+		/* must copy state data before unlocking buffer */
+		xwait = HeapTupleHeaderGetRawXmax(oldtup.t_data);
+		infomask = oldtup.t_data->t_infomask;
+
+		/*
+		 * Now we have to do something about the existing locker.  If it's a
+		 * multi, sleep on it; we might be awakened before it is completely
+		 * gone (or even not sleep at all in some cases); we need to preserve
+		 * it as locker, unless it is gone completely.
+		 *
+		 * If it's not a multi, we need to check for sleeping conditions
+		 * before actually going to sleep.  If the update doesn't conflict
+		 * with the locks, we just continue without sleeping (but making sure
+		 * it is preserved).
+		 *
+		 * Before sleeping, we need to acquire tuple lock to establish our
+		 * priority for the tuple (see heap_lock_tuple).  LockTuple will
+		 * release us when we are next-in-line for the tuple.  Note we must
+		 * not acquire the tuple lock until we're sure we're going to sleep;
+		 * otherwise we're open for race conditions with other transactions
+		 * holding the tuple lock which sleep on us.
+		 *
+		 * If we are forced to "start over" below, we keep the tuple lock;
+		 * this arranges that we stay at the head of the line while rechecking
+		 * tuple state.
+		 */
+		if (infomask & HEAP_XMAX_IS_MULTI)
+		{
+			TransactionId update_xact;
+			int			remain;
+			bool		current_is_member = false;
+
+			if (DoesMultiXactIdConflict((MultiXactId) xwait, infomask,
+										*lockmode, &current_is_member))
+			{
+				LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+
+				/*
+				 * Acquire the lock, if necessary (but skip it when we're
+				 * requesting a lock and already have one; avoids deadlock).
+				 */
+				if (!current_is_member)
+					heap_acquire_tuplock(relation, &(oldtup.t_self), *lockmode,
+										 LockWaitBlock, &have_tuple_lock);
+
+				/* wait for multixact */
+				MultiXactIdWait((MultiXactId) xwait, mxact_status, infomask,
+								relation, &oldtup.t_self, XLTW_Update,
+								&remain);
+				checked_lockers = true;
+				locker_remains = remain != 0;
+				LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+
+				/*
+				 * If xwait had just locked the tuple then some other xact
+				 * could update this tuple before we get to this point.  Check
+				 * for xmax change, and start over if so.
+				 */
+				if (xmax_infomask_changed(oldtup.t_data->t_infomask,
+										  infomask) ||
+					!TransactionIdEquals(HeapTupleHeaderGetRawXmax(oldtup.t_data),
+										 xwait))
+					goto l2;
+			}
+
+			/*
+			 * Note that the multixact may not be done by now.  It could have
+			 * surviving members; our own xact or other subxacts of this
+			 * backend, and also any other concurrent transaction that locked
+			 * the tuple with LockTupleKeyShare if we only got
+			 * LockTupleNoKeyExclusive.  If this is the case, we have to be
+			 * careful to mark the updated tuple with the surviving members in
+			 * Xmax.
+			 *
+			 * Note that there could have been another update in the
+			 * MultiXact. In that case, we need to check whether it committed
+			 * or aborted. If it aborted we are safe to update it again;
+			 * otherwise there is an update conflict, and we have to return
+			 * TableTuple{Deleted, Updated} below.
+			 *
+			 * In the LockTupleExclusive case, we still need to preserve the
+			 * surviving members: those would include the tuple locks we had
+			 * before this one, which are important to keep in case this
+			 * subxact aborts.
+			 */
+			if (!HEAP_XMAX_IS_LOCKED_ONLY(oldtup.t_data->t_infomask))
+				update_xact = HeapTupleGetUpdateXid(oldtup.t_data);
+			else
+				update_xact = InvalidTransactionId;
+
+			/*
+			 * There was no UPDATE in the MultiXact; or it aborted. No
+			 * TransactionIdIsInProgress() call needed here, since we called
+			 * MultiXactIdWait() above.
+			 */
+			if (!TransactionIdIsValid(update_xact) ||
+				TransactionIdDidAbort(update_xact))
+				can_continue = true;
+		}
+		else if (TransactionIdIsCurrentTransactionId(xwait))
+		{
+			/*
+			 * The only locker is ourselves; we can avoid grabbing the tuple
+			 * lock here, but must preserve our locking information.
+			 */
+			checked_lockers = true;
+			locker_remains = true;
+			can_continue = true;
+		}
+		else if (HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) && key_intact)
+		{
+			/*
+			 * If it's just a key-share locker, and we're not changing the key
+			 * columns, we don't need to wait for it to end; but we need to
+			 * preserve it as locker.
+			 */
+			checked_lockers = true;
+			locker_remains = true;
+			can_continue = true;
+		}
+		else
+		{
+			/*
+			 * Wait for regular transaction to end; but first, acquire tuple
+			 * lock.
+			 */
+			LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+			heap_acquire_tuplock(relation, &(oldtup.t_self), *lockmode,
+								 LockWaitBlock, &have_tuple_lock);
+			XactLockTableWait(xwait, relation, &oldtup.t_self,
+							  XLTW_Update);
+			checked_lockers = true;
+			LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+
+			/*
+			 * xwait is done, but if xwait had just locked the tuple then some
+			 * other xact could update this tuple before we get to this point.
+			 * Check for xmax change, and start over if so.
+			 */
+			if (xmax_infomask_changed(oldtup.t_data->t_infomask, infomask) ||
+				!TransactionIdEquals(xwait,
+									 HeapTupleHeaderGetRawXmax(oldtup.t_data)))
+				goto l2;
+
+			/* Otherwise check if it committed or aborted */
+			UpdateXmaxHintBits(oldtup.t_data, buffer, xwait);
+			if (oldtup.t_data->t_infomask & HEAP_XMAX_INVALID)
+				can_continue = true;
+		}
+
+		if (can_continue)
+			result = TM_Ok;
+		else if (!ItemPointerEquals(&oldtup.t_self, &oldtup.t_data->t_ctid))
+			result = TM_Updated;
+		else
+			result = TM_Deleted;
+	}
+
+	if (crosscheck != InvalidSnapshot && result == TM_Ok)
+	{
+		/* Perform additional check for transaction-snapshot mode RI updates */
+		if (!HeapTupleSatisfiesVisibility(&oldtup, crosscheck, buffer))
+		{
+			result = TM_Updated;
+			Assert(!ItemPointerEquals(&oldtup.t_self, &oldtup.t_data->t_ctid));
+		}
+	}
+
+	if (result != TM_Ok)
+	{
+		Assert(result == TM_SelfModified ||
+			   result == TM_Updated ||
+			   result == TM_Deleted ||
+			   result == TM_BeingModified);
+		Assert(!(oldtup.t_data->t_infomask & HEAP_XMAX_INVALID));
+		Assert(result != TM_Updated ||
+			   !ItemPointerEquals(&oldtup.t_self, &oldtup.t_data->t_ctid));
+		tmfd->ctid = oldtup.t_data->t_ctid;
+		tmfd->xmax = HeapTupleHeaderGetUpdateXid(oldtup.t_data);
+		if (result == TM_SelfModified)
+			tmfd->cmax = HeapTupleHeaderGetCmax(oldtup.t_data);
+		else
+			tmfd->cmax = InvalidCommandId;
+		UnlockReleaseBuffer(buffer);
+		if (have_tuple_lock)
+			UnlockTupleTuplock(relation, &(oldtup.t_self), *lockmode);
+		if (vmbuffer != InvalidBuffer)
+			ReleaseBuffer(vmbuffer);
+		bms_free(hot_attrs);
+		bms_free(key_attrs);
+		bms_free(id_attrs);
+		bms_free(modified_attrs);
+		bms_free(interesting_attrs);
+		return result;
+	}
+
+	/*
+	 * If we didn't pin the visibility map page and the page has become all
+	 * visible while we were busy locking the buffer, or during some
+	 * subsequent window during which we had it unlocked, we'll have to unlock
+	 * and re-lock, to avoid holding the buffer lock across an I/O.  That's a
+	 * bit unfortunate, especially since we'll now have to recheck whether the
+	 * tuple has been locked or updated under us, but hopefully it won't
+	 * happen very often.
+	 */
+	if (vmbuffer == InvalidBuffer && PageIsAllVisible(page))
+	{
+		LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+		visibilitymap_pin(relation, block, &vmbuffer);
+		LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+		goto l2;
+	}
+
+	/* Fill in transaction status data */
+
+	/*
+	 * If the tuple we're updating is locked, we need to preserve the locking
+	 * info in the old tuple's Xmax.  Prepare a new Xmax value for this.
+	 */
+	compute_new_xmax_infomask(HeapTupleHeaderGetRawXmax(oldtup.t_data),
+							  oldtup.t_data->t_infomask,
+							  oldtup.t_data->t_infomask2,
+							  xid, *lockmode, true,
+							  &xmax_old_tuple, &infomask_old_tuple,
+							  &infomask2_old_tuple);
+
+	/*
+	 * And also prepare an Xmax value for the new copy of the tuple.  If there
+	 * was no xmax previously, or there was one but all lockers are now gone,
+	 * then use InvalidTransactionId; otherwise, get the xmax from the old
+	 * tuple.  (In rare cases that might also be InvalidTransactionId and yet
+	 * not have the HEAP_XMAX_INVALID bit set; that's fine.)
+	 */
+	if ((oldtup.t_data->t_infomask & HEAP_XMAX_INVALID) ||
+		HEAP_LOCKED_UPGRADED(oldtup.t_data->t_infomask) ||
+		(checked_lockers && !locker_remains))
+		xmax_new_tuple = InvalidTransactionId;
+	else
+		xmax_new_tuple = HeapTupleHeaderGetRawXmax(oldtup.t_data);
+
+	if (!TransactionIdIsValid(xmax_new_tuple))
+	{
+		infomask_new_tuple = HEAP_XMAX_INVALID;
+		infomask2_new_tuple = 0;
+	}
+	else
+	{
+		/*
+		 * If we found a valid Xmax for the new tuple, then the infomask bits
+		 * to use on the new tuple depend on what was there on the old one.
+		 * Note that since we're doing an update, the only possibility is that
+		 * the lockers had FOR KEY SHARE lock.
+		 */
+		if (oldtup.t_data->t_infomask & HEAP_XMAX_IS_MULTI)
+		{
+			GetMultiXactIdHintBits(xmax_new_tuple, &infomask_new_tuple,
+								   &infomask2_new_tuple);
+		}
+		else
+		{
+			infomask_new_tuple = HEAP_XMAX_KEYSHR_LOCK | HEAP_XMAX_LOCK_ONLY;
+			infomask2_new_tuple = 0;
+		}
+	}
+
+	/*
+	 * Prepare the new tuple with the appropriate initial values of Xmin and
+	 * Xmax, as well as initial infomask bits as computed above.
+	 */
+	newtup->t_data->t_infomask &= ~(HEAP_XACT_MASK);
+	newtup->t_data->t_infomask2 &= ~(HEAP2_XACT_MASK);
+	HeapTupleHeaderSetXmin(newtup->t_data, xid);
+	HeapTupleHeaderSetCmin(newtup->t_data, cid);
+	newtup->t_data->t_infomask |= HEAP_UPDATED | infomask_new_tuple;
+	newtup->t_data->t_infomask2 |= infomask2_new_tuple;
+	HeapTupleHeaderSetXmax(newtup->t_data, xmax_new_tuple);
+
+	/*
+	 * Replace cid with a combo CID if necessary.  Note that we already put
+	 * the plain cid into the new tuple.
+	 */
+	HeapTupleHeaderAdjustCmax(oldtup.t_data, &cid, &iscombo);
+
+	/*
+	 * If the toaster needs to be activated, OR if the new tuple will not fit
+	 * on the same page as the old, then we need to release the content lock
+	 * (but not the pin!) on the old tuple's buffer while we are off doing
+	 * TOAST and/or table-file-extension work.  We must mark the old tuple to
+	 * show that it's locked, else other processes may try to update it
+	 * themselves.
+	 *
+	 * We need to invoke the toaster if there are already any out-of-line
+	 * toasted values present, or if the new tuple is over-threshold.
+	 */
+	if (relation->rd_rel->relkind != RELKIND_RELATION &&
+		relation->rd_rel->relkind != RELKIND_MATVIEW)
+	{
+		/* toast table entries should never be recursively toasted */
+		Assert(!HeapTupleHasExternal(&oldtup));
+		Assert(!HeapTupleHasExternal(newtup));
+		need_toast = false;
+	}
+	else
+		need_toast = (HeapTupleHasExternal(&oldtup) ||
+					  HeapTupleHasExternal(newtup) ||
+					  newtup->t_len > TOAST_TUPLE_THRESHOLD);
+
+	pagefree = PageGetHeapFreeSpace(page);
+
+	newtupsize = MAXALIGN(newtup->t_len);
+
+	if (need_toast || newtupsize > pagefree)
+	{
+		TransactionId xmax_lock_old_tuple;
+		uint16		infomask_lock_old_tuple,
+					infomask2_lock_old_tuple;
+		bool		cleared_all_frozen = false;
+
+		/*
+		 * To prevent concurrent sessions from updating the tuple, we have to
+		 * temporarily mark it locked, while we release the page-level lock.
+		 *
+		 * To satisfy the rule that any xid potentially appearing in a buffer
+		 * written out to disk, we unfortunately have to WAL log this
+		 * temporary modification.  We can reuse xl_heap_lock for this
+		 * purpose.  If we crash/error before following through with the
+		 * actual update, xmax will be of an aborted transaction, allowing
+		 * other sessions to proceed.
+		 */
+
+		/*
+		 * Compute xmax / infomask appropriate for locking the tuple. This has
+		 * to be done separately from the combo that's going to be used for
+		 * updating, because the potentially created multixact would otherwise
+		 * be wrong.
+		 */
+		compute_new_xmax_infomask(HeapTupleHeaderGetRawXmax(oldtup.t_data),
+								  oldtup.t_data->t_infomask,
+								  oldtup.t_data->t_infomask2,
+								  xid, *lockmode, false,
+								  &xmax_lock_old_tuple, &infomask_lock_old_tuple,
+								  &infomask2_lock_old_tuple);
+
+		Assert(HEAP_XMAX_IS_LOCKED_ONLY(infomask_lock_old_tuple));
+
+		START_CRIT_SECTION();
+
+		/* Clear obsolete visibility flags ... */
+		oldtup.t_data->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED);
+		oldtup.t_data->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+		HeapTupleClearHotUpdated(&oldtup);
+		/* ... and store info about transaction updating this tuple */
+		Assert(TransactionIdIsValid(xmax_lock_old_tuple));
+		HeapTupleHeaderSetXmax(oldtup.t_data, xmax_lock_old_tuple);
+		oldtup.t_data->t_infomask |= infomask_lock_old_tuple;
+		oldtup.t_data->t_infomask2 |= infomask2_lock_old_tuple;
+		HeapTupleHeaderSetCmax(oldtup.t_data, cid, iscombo);
+
+		/* temporarily make it look not-updated, but locked */
+		oldtup.t_data->t_ctid = oldtup.t_self;
+
+		/*
+		 * Clear all-frozen bit on visibility map if needed. We could
+		 * immediately reset ALL_VISIBLE, but given that the WAL logging
+		 * overhead would be unchanged, that doesn't seem necessarily
+		 * worthwhile.
+		 */
+		if (PageIsAllVisible(page) &&
+			visibilitymap_clear(relation, block, vmbuffer,
+								VISIBILITYMAP_ALL_FROZEN))
+			cleared_all_frozen = true;
+
+		MarkBufferDirty(buffer);
+
+		if (RelationNeedsWAL(relation))
+		{
+			xl_heap_lock xlrec;
+			XLogRecPtr	recptr;
+
+			XLogBeginInsert();
+			XLogRegisterBuffer(0, buffer, REGBUF_STANDARD);
+
+			xlrec.offnum = ItemPointerGetOffsetNumber(&oldtup.t_self);
+			xlrec.locking_xid = xmax_lock_old_tuple;
+			xlrec.infobits_set = compute_infobits(oldtup.t_data->t_infomask,
+												  oldtup.t_data->t_infomask2);
+			xlrec.flags =
+				cleared_all_frozen ? XLH_LOCK_ALL_FROZEN_CLEARED : 0;
+			XLogRegisterData((char *) &xlrec, SizeOfHeapLock);
+			recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_LOCK);
+			PageSetLSN(page, recptr);
+		}
+
+		END_CRIT_SECTION();
+
+		LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+
+		/*
+		 * Let the toaster do its thing, if needed.
+		 *
+		 * Note: below this point, heaptup is the data we actually intend to
+		 * store into the relation; newtup is the caller's original untoasted
+		 * data.
+		 */
+		if (need_toast)
+		{
+			/* Note we always use WAL and FSM during updates */
+			heaptup = heap_toast_insert_or_update(relation, newtup, &oldtup, 0);
+			newtupsize = MAXALIGN(heaptup->t_len);
+		}
+		else
+			heaptup = newtup;
+
+		/*
+		 * Now, do we need a new page for the tuple, or not?  This is a bit
+		 * tricky since someone else could have added tuples to the page while
+		 * we weren't looking.  We have to recheck the available space after
+		 * reacquiring the buffer lock.  But don't bother to do that if the
+		 * former amount of free space is still not enough; it's unlikely
+		 * there's more free now than before.
+		 *
+		 * What's more, if we need to get a new page, we will need to acquire
+		 * buffer locks on both old and new pages.  To avoid deadlock against
+		 * some other backend trying to get the same two locks in the other
+		 * order, we must be consistent about the order we get the locks in.
+		 * We use the rule "lock the lower-numbered page of the relation
+		 * first".  To implement this, we must do RelationGetBufferForTuple
+		 * while not holding the lock on the old page, and we must rely on it
+		 * to get the locks on both pages in the correct order.
+		 *
+		 * Another consideration is that we need visibility map page pin(s) if
+		 * we will have to clear the all-visible flag on either page.  If we
+		 * call RelationGetBufferForTuple, we rely on it to acquire any such
+		 * pins; but if we don't, we have to handle that here.  Hence we need
+		 * a loop.
+		 */
+		for (;;)
+		{
+			if (newtupsize > pagefree)
+			{
+				/* It doesn't fit, must use RelationGetBufferForTuple. */
+				newbuf = RelationGetBufferForTuple(relation, heaptup->t_len,
+												   buffer, 0, NULL,
+												   &vmbuffer_new, &vmbuffer);
+				/* We're all done. */
+				break;
+			}
+			/* Acquire VM page pin if needed and we don't have it. */
+			if (vmbuffer == InvalidBuffer && PageIsAllVisible(page))
+				visibilitymap_pin(relation, block, &vmbuffer);
+			/* Re-acquire the lock on the old tuple's page. */
+			LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+			/* Re-check using the up-to-date free space */
+			pagefree = PageGetHeapFreeSpace(page);
+			if (newtupsize > pagefree ||
+				(vmbuffer == InvalidBuffer && PageIsAllVisible(page)))
+			{
+				/*
+				 * Rats, it doesn't fit anymore, or somebody just now set the
+				 * all-visible flag.  We must now unlock and loop to avoid
+				 * deadlock.  Fortunately, this path should seldom be taken.
+				 */
+				LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+			}
+			else
+			{
+				/* We're all done. */
+				newbuf = buffer;
+				break;
+			}
+		}
+	}
+	else
+	{
+		/* No TOAST work needed, and it'll fit on same page */
+		newbuf = buffer;
+		heaptup = newtup;
+	}
+
+	/*
+	 * We're about to do the actual update -- check for conflict first, to
+	 * avoid possibly having to roll back work we've just done.
+	 *
+	 * This is safe without a recheck as long as there is no possibility of
+	 * another process scanning the pages between this check and the update
+	 * being visible to the scan (i.e., exclusive buffer content lock(s) are
+	 * continuously held from this point until the tuple update is visible).
+	 *
+	 * For the new tuple the only check needed is at the relation level, but
+	 * since both tuples are in the same relation and the check for oldtup
+	 * will include checking the relation level, there is no benefit to a
+	 * separate check for the new tuple.
+	 */
+	CheckForSerializableConflictIn(relation, &oldtup.t_self,
+								   BufferGetBlockNumber(buffer));
+
+	/*
+	 * At this point newbuf and buffer are both pinned and locked, and newbuf
+	 * has enough space for the new tuple.  If they are the same buffer, only
+	 * one pin is held.
+	 */
+
+	if (newbuf == buffer)
+	{
+		/*
+		 * Since the new tuple is going into the same page, we might be able
+		 * to do a HOT update.  Check if any of the index columns have been
+		 * changed.
+		 */
+		if (!bms_overlap(modified_attrs, hot_attrs))
+			use_hot_update = true;
+	}
+	else
+	{
+		/* Set a hint that the old page could use prune/defrag */
+		PageSetFull(page);
+	}
+
+	/*
+	 * Compute replica identity tuple before entering the critical section so
+	 * we don't PANIC upon a memory allocation failure.
+	 * ExtractReplicaIdentity() will return NULL if nothing needs to be
+	 * logged.  Pass old key required as true only if the replica identity key
+	 * columns are modified or it has external data.
+	 */
+	old_key_tuple = ExtractReplicaIdentity(relation, &oldtup,
+										   bms_overlap(modified_attrs, id_attrs) ||
+										   id_has_external,
+										   &old_key_copied);
+
+	/* NO EREPORT(ERROR) from here till changes are logged */
+	START_CRIT_SECTION();
+
+	/*
+	 * If this transaction commits, the old tuple will become DEAD sooner or
+	 * later.  Set flag that this page is a candidate for pruning once our xid
+	 * falls below the OldestXmin horizon.  If the transaction finally aborts,
+	 * the subsequent page pruning will be a no-op and the hint will be
+	 * cleared.
+	 *
+	 * XXX Should we set hint on newbuf as well?  If the transaction aborts,
+	 * there would be a prunable tuple in the newbuf; but for now we choose
+	 * not to optimize for aborts.  Note that heap_xlog_update must be kept in
+	 * sync if this decision changes.
+	 */
+	PageSetPrunable(page, xid);
+
+	if (use_hot_update)
+	{
+		/* Mark the old tuple as HOT-updated */
+		HeapTupleSetHotUpdated(&oldtup);
+		/* And mark the new tuple as heap-only */
+		HeapTupleSetHeapOnly(heaptup);
+		/* Mark the caller's copy too, in case different from heaptup */
+		HeapTupleSetHeapOnly(newtup);
+	}
+	else
+	{
+		/* Make sure tuples are correctly marked as not-HOT */
+		HeapTupleClearHotUpdated(&oldtup);
+		HeapTupleClearHeapOnly(heaptup);
+		HeapTupleClearHeapOnly(newtup);
+	}
+
+	RelationPutHeapTuple(relation, newbuf, heaptup, false); /* insert new tuple */
+
+
+	/* Clear obsolete visibility flags, possibly set by ourselves above... */
+	oldtup.t_data->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED);
+	oldtup.t_data->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+	/* ... and store info about transaction updating this tuple */
+	Assert(TransactionIdIsValid(xmax_old_tuple));
+	HeapTupleHeaderSetXmax(oldtup.t_data, xmax_old_tuple);
+	oldtup.t_data->t_infomask |= infomask_old_tuple;
+	oldtup.t_data->t_infomask2 |= infomask2_old_tuple;
+	HeapTupleHeaderSetCmax(oldtup.t_data, cid, iscombo);
+
+	/* record address of new tuple in t_ctid of old one */
+	oldtup.t_data->t_ctid = heaptup->t_self;
+
+	/* clear PD_ALL_VISIBLE flags, reset all visibilitymap bits */
+	if (PageIsAllVisible(BufferGetPage(buffer)))
+	{
+		all_visible_cleared = true;
+		PageClearAllVisible(BufferGetPage(buffer));
+		visibilitymap_clear(relation, BufferGetBlockNumber(buffer),
+							vmbuffer, VISIBILITYMAP_VALID_BITS);
+	}
+	if (newbuf != buffer && PageIsAllVisible(BufferGetPage(newbuf)))
+	{
+		all_visible_cleared_new = true;
+		PageClearAllVisible(BufferGetPage(newbuf));
+		visibilitymap_clear(relation, BufferGetBlockNumber(newbuf),
+							vmbuffer_new, VISIBILITYMAP_VALID_BITS);
+	}
+
+	if (newbuf != buffer)
+		MarkBufferDirty(newbuf);
+	MarkBufferDirty(buffer);
+
+	/* XLOG stuff */
+	if (RelationNeedsWAL(relation))
+	{
+		XLogRecPtr	recptr;
+
+		/*
+		 * For logical decoding we need combo CIDs to properly decode the
+		 * catalog.
+		 */
+		if (RelationIsAccessibleInLogicalDecoding(relation))
+		{
+			log_heap_new_cid(relation, &oldtup);
+			log_heap_new_cid(relation, heaptup);
+		}
+
+		recptr = log_heap_update(relation, buffer,
+								 newbuf, &oldtup, heaptup,
+								 old_key_tuple,
+								 all_visible_cleared,
+								 all_visible_cleared_new);
+		if (newbuf != buffer)
+		{
+			PageSetLSN(BufferGetPage(newbuf), recptr);
+		}
+		PageSetLSN(BufferGetPage(buffer), recptr);
+	}
+
+	END_CRIT_SECTION();
+
+	if (newbuf != buffer)
+		LockBuffer(newbuf, BUFFER_LOCK_UNLOCK);
+	LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+
+	/*
+	 * Mark old tuple for invalidation from system caches at next command
+	 * boundary, and mark the new tuple for invalidation in case we abort. We
+	 * have to do this before releasing the buffer because oldtup is in the
+	 * buffer.  (heaptup is all in local memory, but it's necessary to process
+	 * both tuple versions in one call to inval.c so we can avoid redundant
+	 * sinval messages.)
+	 */
+	CacheInvalidateHeapTuple(relation, &oldtup, heaptup);
+
+	/* Now we can release the buffer(s) */
+	if (newbuf != buffer)
+		ReleaseBuffer(newbuf);
+	ReleaseBuffer(buffer);
+	if (BufferIsValid(vmbuffer_new))
+		ReleaseBuffer(vmbuffer_new);
+	if (BufferIsValid(vmbuffer))
+		ReleaseBuffer(vmbuffer);
+
+	/*
+	 * Release the lmgr tuple lock, if we had it.
+	 */
+	if (have_tuple_lock)
+		UnlockTupleTuplock(relation, &(oldtup.t_self), *lockmode);
+
+	pgstat_count_heap_update(relation, use_hot_update);
+
+	/*
+	 * If heaptup is a private copy, release it.  Don't forget to copy t_self
+	 * back to the caller's image, too.
+	 */
+	if (heaptup != newtup)
+	{
+		newtup->t_self = heaptup->t_self;
+		heap_freetuple(heaptup);
+	}
+
+	if (old_key_tuple != NULL && old_key_copied)
+		heap_freetuple(old_key_tuple);
+
+	bms_free(hot_attrs);
+	bms_free(key_attrs);
+	bms_free(id_attrs);
+	bms_free(modified_attrs);
+	bms_free(interesting_attrs);
+
+	return TM_Ok;
+}
+
+/*
+ * Check if the specified attribute's values are the same.  Subroutine for
+ * HeapDetermineColumnsInfo.
+ */
+static bool
+heap_attr_equals(TupleDesc tupdesc, int attrnum, Datum value1, Datum value2,
+				 bool isnull1, bool isnull2)
+{
+	Form_pg_attribute att;
+
+	/*
+	 * If one value is NULL and other is not, then they are certainly not
+	 * equal
+	 */
+	if (isnull1 != isnull2)
+		return false;
+
+	/*
+	 * If both are NULL, they can be considered equal.
+	 */
+	if (isnull1)
+		return true;
+
+	/*
+	 * We do simple binary comparison of the two datums.  This may be overly
+	 * strict because there can be multiple binary representations for the
+	 * same logical value.  But we should be OK as long as there are no false
+	 * positives.  Using a type-specific equality operator is messy because
+	 * there could be multiple notions of equality in different operator
+	 * classes; furthermore, we cannot safely invoke user-defined functions
+	 * while holding exclusive buffer lock.
+	 */
+	if (attrnum <= 0)
+	{
+		/* The only allowed system columns are OIDs, so do this */
+		return (DatumGetObjectId(value1) == DatumGetObjectId(value2));
+	}
+	else
+	{
+		Assert(attrnum <= tupdesc->natts);
+		att = TupleDescAttr(tupdesc, attrnum - 1);
+		return datumIsEqual(value1, value2, att->attbyval, att->attlen);
+	}
+}
+
+/*
+ * Check which columns are being updated.
+ *
+ * Given an updated tuple, determine (and return into the output bitmapset),
+ * from those listed as interesting, the set of columns that changed.
+ *
+ * has_external indicates if any of the unmodified attributes (from those
+ * listed as interesting) of the old tuple is a member of external_cols and is
+ * stored externally.
+ *
+ * The input interesting_cols bitmapset is destructively modified; that is OK
+ * since this is invoked at most once in heap_update.
+ */
+static Bitmapset *
+HeapDetermineColumnsInfo(Relation relation,
+						 Bitmapset *interesting_cols,
+						 Bitmapset *external_cols,
+						 HeapTuple oldtup, HeapTuple newtup,
+						 bool *has_external)
+{
+	int			attrnum;
+	Bitmapset  *modified = NULL;
+	TupleDesc	tupdesc = RelationGetDescr(relation);
+
+	while ((attrnum = bms_first_member(interesting_cols)) >= 0)
+	{
+		Datum		value1,
+					value2;
+		bool		isnull1,
+					isnull2;
+
+		attrnum += FirstLowInvalidHeapAttributeNumber;
+
+		/*
+		 * If it's a whole-tuple reference, say "not equal".  It's not really
+		 * worth supporting this case, since it could only succeed after a
+		 * no-op update, which is hardly a case worth optimizing for.
+		 */
+		if (attrnum == 0)
+		{
+			modified = bms_add_member(modified,
+									  attrnum -
+									  FirstLowInvalidHeapAttributeNumber);
+			continue;
+		}
+
+		/*
+		 * Likewise, automatically say "not equal" for any system attribute
+		 * other than tableOID; we cannot expect these to be consistent in a
+		 * HOT chain, or even to be set correctly yet in the new tuple.
+		 */
+		if (attrnum < 0)
+		{
+			if (attrnum != TableOidAttributeNumber)
+			{
+				modified = bms_add_member(modified,
+										  attrnum -
+										  FirstLowInvalidHeapAttributeNumber);
+				continue;
+			}
+		}
+
+		/*
+		 * Extract the corresponding values.  XXX this is pretty inefficient
+		 * if there are many indexed columns.  Should we do a single
+		 * heap_deform_tuple call on each tuple, instead?	But that doesn't
+		 * work for system columns ...
+		 */
+		value1 = heap_getattr(oldtup, attrnum, tupdesc, &isnull1);
+		value2 = heap_getattr(newtup, attrnum, tupdesc, &isnull2);
+
+		if (!heap_attr_equals(tupdesc, attrnum, value1,
+							  value2, isnull1, isnull2))
+		{
+			modified = bms_add_member(modified,
+									  attrnum -
+									  FirstLowInvalidHeapAttributeNumber);
+			continue;
+		}
+
+		/*
+		 * No need to check attributes that can't be stored externally. Note
+		 * that system attributes can't be stored externally.
+		 */
+		if (attrnum < 0 || isnull1 ||
+			TupleDescAttr(tupdesc, attrnum - 1)->attlen != -1)
+			continue;
+
+		/*
+		 * Check if the old tuple's attribute is stored externally and is a
+		 * member of external_cols.
+		 */
+		if (VARATT_IS_EXTERNAL((struct varlena *) DatumGetPointer(value1)) &&
+			bms_is_member(attrnum - FirstLowInvalidHeapAttributeNumber,
+						  external_cols))
+			*has_external = true;
+	}
+
+	return modified;
+}
+
+/*
+ *	simple_heap_update - replace a tuple
+ *
+ * This routine may be used to update a tuple when concurrent updates of
+ * the target tuple are not expected (for example, because we have a lock
+ * on the relation associated with the tuple).  Any failure is reported
+ * via ereport().
+ */
+void
+simple_heap_update(Relation relation, ItemPointer otid, HeapTuple tup)
+{
+	TM_Result	result;
+	TM_FailureData tmfd;
+	LockTupleMode lockmode;
+
+	result = heap_update(relation, otid, tup,
+						 GetCurrentCommandId(true), InvalidSnapshot,
+						 true /* wait for commit */ ,
+						 &tmfd, &lockmode);
+	switch (result)
+	{
+		case TM_SelfModified:
+			/* Tuple was already updated in current command? */
+			elog(ERROR, "tuple already updated by self");
+			break;
+
+		case TM_Ok:
+			/* done successfully */
+			break;
+
+		case TM_Updated:
+			elog(ERROR, "tuple concurrently updated");
+			break;
+
+		case TM_Deleted:
+			elog(ERROR, "tuple concurrently deleted");
+			break;
+
+		default:
+			elog(ERROR, "unrecognized heap_update status: %u", result);
+			break;
+	}
+}
+
+
+/*
+ * Return the MultiXactStatus corresponding to the given tuple lock mode.
+ */
+static MultiXactStatus
+get_mxact_status_for_lock(LockTupleMode mode, bool is_update)
+{
+	int			retval;
+
+	if (is_update)
+		retval = tupleLockExtraInfo[mode].updstatus;
+	else
+		retval = tupleLockExtraInfo[mode].lockstatus;
+
+	if (retval == -1)
+		elog(ERROR, "invalid lock tuple mode %d/%s", mode,
+			 is_update ? "true" : "false");
+
+	return (MultiXactStatus) retval;
+}
+
+/*
+ *	heap_lock_tuple - lock a tuple in shared or exclusive mode
+ *
+ * Note that this acquires a buffer pin, which the caller must release.
+ *
+ * Input parameters:
+ *	relation: relation containing tuple (caller must hold suitable lock)
+ *	tid: TID of tuple to lock
+ *	cid: current command ID (used for visibility test, and stored into
+ *		tuple's cmax if lock is successful)
+ *	mode: indicates if shared or exclusive tuple lock is desired
+ *	wait_policy: what to do if tuple lock is not available
+ *	follow_updates: if true, follow the update chain to also lock descendant
+ *		tuples.
+ *
+ * Output parameters:
+ *	*tuple: all fields filled in
+ *	*buffer: set to buffer holding tuple (pinned but not locked at exit)
+ *	*tmfd: filled in failure cases (see below)
+ *
+ * Function results are the same as the ones for table_tuple_lock().
+ *
+ * In the failure cases other than TM_Invisible, the routine fills
+ * *tmfd with the tuple's t_ctid, t_xmax (resolving a possible MultiXact,
+ * if necessary), and t_cmax (the last only for TM_SelfModified,
+ * since we cannot obtain cmax from a combo CID generated by another
+ * transaction).
+ * See comments for struct TM_FailureData for additional info.
+ *
+ * See README.tuplock for a thorough explanation of this mechanism.
+ */
+TM_Result
+heap_lock_tuple(Relation relation, HeapTuple tuple,
+				CommandId cid, LockTupleMode mode, LockWaitPolicy wait_policy,
+				bool follow_updates,
+				Buffer *buffer, TM_FailureData *tmfd)
+{
+	TM_Result	result;
+	ItemPointer tid = &(tuple->t_self);
+	ItemId		lp;
+	Page		page;
+	Buffer		vmbuffer = InvalidBuffer;
+	BlockNumber block;
+	TransactionId xid,
+				xmax;
+	uint16		old_infomask,
+				new_infomask,
+				new_infomask2;
+	bool		first_time = true;
+	bool		skip_tuple_lock = false;
+	bool		have_tuple_lock = false;
+	bool		cleared_all_frozen = false;
+
+	*buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));
+	block = ItemPointerGetBlockNumber(tid);
+
+	/*
+	 * Before locking the buffer, pin the visibility map page if it appears to
+	 * be necessary.  Since we haven't got the lock yet, someone else might be
+	 * in the middle of changing this, so we'll need to recheck after we have
+	 * the lock.
+	 */
+	if (PageIsAllVisible(BufferGetPage(*buffer)))
+		visibilitymap_pin(relation, block, &vmbuffer);
+
+	LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+
+	page = BufferGetPage(*buffer);
+	lp = PageGetItemId(page, ItemPointerGetOffsetNumber(tid));
+	Assert(ItemIdIsNormal(lp));
+
+	tuple->t_data = (HeapTupleHeader) PageGetItem(page, lp);
+	tuple->t_len = ItemIdGetLength(lp);
+	tuple->t_tableOid = RelationGetRelid(relation);
+
+l3:
+	result = HeapTupleSatisfiesUpdate(tuple, cid, *buffer);
+
+	if (result == TM_Invisible)
+	{
+		/*
+		 * This is possible, but only when locking a tuple for ON CONFLICT
+		 * UPDATE.  We return this value here rather than throwing an error in
+		 * order to give that case the opportunity to throw a more specific
+		 * error.
+		 */
+		result = TM_Invisible;
+		goto out_locked;
+	}
+	else if (result == TM_BeingModified ||
+			 result == TM_Updated ||
+			 result == TM_Deleted)
+	{
+		TransactionId xwait;
+		uint16		infomask;
+		uint16		infomask2;
+		bool		require_sleep;
+		ItemPointerData t_ctid;
+
+		/* must copy state data before unlocking buffer */
+		xwait = HeapTupleHeaderGetRawXmax(tuple->t_data);
+		infomask = tuple->t_data->t_infomask;
+		infomask2 = tuple->t_data->t_infomask2;
+		ItemPointerCopy(&tuple->t_data->t_ctid, &t_ctid);
+
+		LockBuffer(*buffer, BUFFER_LOCK_UNLOCK);
+
+		/*
+		 * If any subtransaction of the current top transaction already holds
+		 * a lock as strong as or stronger than what we're requesting, we
+		 * effectively hold the desired lock already.  We *must* succeed
+		 * without trying to take the tuple lock, else we will deadlock
+		 * against anyone wanting to acquire a stronger lock.
+		 *
+		 * Note we only do this the first time we loop on the HTSU result;
+		 * there is no point in testing in subsequent passes, because
+		 * evidently our own transaction cannot have acquired a new lock after
+		 * the first time we checked.
+		 */
+		if (first_time)
+		{
+			first_time = false;
+
+			if (infomask & HEAP_XMAX_IS_MULTI)
+			{
+				int			i;
+				int			nmembers;
+				MultiXactMember *members;
+
+				/*
+				 * We don't need to allow old multixacts here; if that had
+				 * been the case, HeapTupleSatisfiesUpdate would have returned
+				 * MayBeUpdated and we wouldn't be here.
+				 */
+				nmembers =
+					GetMultiXactIdMembers(xwait, &members, false,
+										  HEAP_XMAX_IS_LOCKED_ONLY(infomask));
+
+				for (i = 0; i < nmembers; i++)
+				{
+					/* only consider members of our own transaction */
+					if (!TransactionIdIsCurrentTransactionId(members[i].xid))
+						continue;
+
+					if (TUPLOCK_from_mxstatus(members[i].status) >= mode)
+					{
+						pfree(members);
+						result = TM_Ok;
+						goto out_unlocked;
+					}
+					else
+					{
+						/*
+						 * Disable acquisition of the heavyweight tuple lock.
+						 * Otherwise, when promoting a weaker lock, we might
+						 * deadlock with another locker that has acquired the
+						 * heavyweight tuple lock and is waiting for our
+						 * transaction to finish.
+						 *
+						 * Note that in this case we still need to wait for
+						 * the multixact if required, to avoid acquiring
+						 * conflicting locks.
+						 */
+						skip_tuple_lock = true;
+					}
+				}
+
+				if (members)
+					pfree(members);
+			}
+			else if (TransactionIdIsCurrentTransactionId(xwait))
+			{
+				switch (mode)
+				{
+					case LockTupleKeyShare:
+						Assert(HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) ||
+							   HEAP_XMAX_IS_SHR_LOCKED(infomask) ||
+							   HEAP_XMAX_IS_EXCL_LOCKED(infomask));
+						result = TM_Ok;
+						goto out_unlocked;
+					case LockTupleShare:
+						if (HEAP_XMAX_IS_SHR_LOCKED(infomask) ||
+							HEAP_XMAX_IS_EXCL_LOCKED(infomask))
+						{
+							result = TM_Ok;
+							goto out_unlocked;
+						}
+						break;
+					case LockTupleNoKeyExclusive:
+						if (HEAP_XMAX_IS_EXCL_LOCKED(infomask))
+						{
+							result = TM_Ok;
+							goto out_unlocked;
+						}
+						break;
+					case LockTupleExclusive:
+						if (HEAP_XMAX_IS_EXCL_LOCKED(infomask) &&
+							infomask2 & HEAP_KEYS_UPDATED)
+						{
+							result = TM_Ok;
+							goto out_unlocked;
+						}
+						break;
+				}
+			}
+		}
+
+		/*
+		 * Initially assume that we will have to wait for the locking
+		 * transaction(s) to finish.  We check various cases below in which
+		 * this can be turned off.
+		 */
+		require_sleep = true;
+		if (mode == LockTupleKeyShare)
+		{
+			/*
+			 * If we're requesting KeyShare, and there's no update present, we
+			 * don't need to wait.  Even if there is an update, we can still
+			 * continue if the key hasn't been modified.
+			 *
+			 * However, if there are updates, we need to walk the update chain
+			 * to mark future versions of the row as locked, too.  That way,
+			 * if somebody deletes that future version, we're protected
+			 * against the key going away.  This locking of future versions
+			 * could block momentarily, if a concurrent transaction is
+			 * deleting a key; or it could return a value to the effect that
+			 * the transaction deleting the key has already committed.  So we
+			 * do this before re-locking the buffer; otherwise this would be
+			 * prone to deadlocks.
+			 *
+			 * Note that the TID we're locking was grabbed before we unlocked
+			 * the buffer.  For it to change while we're not looking, the
+			 * other properties we're testing for below after re-locking the
+			 * buffer would also change, in which case we would restart this
+			 * loop above.
+			 */
+			if (!(infomask2 & HEAP_KEYS_UPDATED))
+			{
+				bool		updated;
+
+				updated = !HEAP_XMAX_IS_LOCKED_ONLY(infomask);
+
+				/*
+				 * If there are updates, follow the update chain; bail out if
+				 * that cannot be done.
+				 */
+				if (follow_updates && updated)
+				{
+					TM_Result	res;
+
+					res = heap_lock_updated_tuple(relation, tuple, &t_ctid,
+												  GetCurrentTransactionId(),
+												  mode);
+					if (res != TM_Ok)
+					{
+						result = res;
+						/* recovery code expects to have buffer lock held */
+						LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+						goto failed;
+					}
+				}
+
+				LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+
+				/*
+				 * Make sure it's still an appropriate lock, else start over.
+				 * Also, if it wasn't updated before we released the lock, but
+				 * is updated now, we start over too; the reason is that we
+				 * now need to follow the update chain to lock the new
+				 * versions.
+				 */
+				if (!HeapTupleHeaderIsOnlyLocked(tuple->t_data) &&
+					((tuple->t_data->t_infomask2 & HEAP_KEYS_UPDATED) ||
+					 !updated))
+					goto l3;
+
+				/* Things look okay, so we can skip sleeping */
+				require_sleep = false;
+
+				/*
+				 * Note we allow Xmax to change here; other updaters/lockers
+				 * could have modified it before we grabbed the buffer lock.
+				 * However, this is not a problem, because with the recheck we
+				 * just did we ensure that they still don't conflict with the
+				 * lock we want.
+				 */
+			}
+		}
+		else if (mode == LockTupleShare)
+		{
+			/*
+			 * If we're requesting Share, we can similarly avoid sleeping if
+			 * there's no update and no exclusive lock present.
+			 */
+			if (HEAP_XMAX_IS_LOCKED_ONLY(infomask) &&
+				!HEAP_XMAX_IS_EXCL_LOCKED(infomask))
+			{
+				LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+
+				/*
+				 * Make sure it's still an appropriate lock, else start over.
+				 * See above about allowing xmax to change.
+				 */
+				if (!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_data->t_infomask) ||
+					HEAP_XMAX_IS_EXCL_LOCKED(tuple->t_data->t_infomask))
+					goto l3;
+				require_sleep = false;
+			}
+		}
+		else if (mode == LockTupleNoKeyExclusive)
+		{
+			/*
+			 * If we're requesting NoKeyExclusive, we might also be able to
+			 * avoid sleeping; just ensure that there no conflicting lock
+			 * already acquired.
+			 */
+			if (infomask & HEAP_XMAX_IS_MULTI)
+			{
+				if (!DoesMultiXactIdConflict((MultiXactId) xwait, infomask,
+											 mode, NULL))
+				{
+					/*
+					 * No conflict, but if the xmax changed under us in the
+					 * meantime, start over.
+					 */
+					LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+					if (xmax_infomask_changed(tuple->t_data->t_infomask, infomask) ||
+						!TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple->t_data),
+											 xwait))
+						goto l3;
+
+					/* otherwise, we're good */
+					require_sleep = false;
+				}
+			}
+			else if (HEAP_XMAX_IS_KEYSHR_LOCKED(infomask))
+			{
+				LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+
+				/* if the xmax changed in the meantime, start over */
+				if (xmax_infomask_changed(tuple->t_data->t_infomask, infomask) ||
+					!TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple->t_data),
+										 xwait))
+					goto l3;
+				/* otherwise, we're good */
+				require_sleep = false;
+			}
+		}
+
+		/*
+		 * As a check independent from those above, we can also avoid sleeping
+		 * if the current transaction is the sole locker of the tuple.  Note
+		 * that the strength of the lock already held is irrelevant; this is
+		 * not about recording the lock in Xmax (which will be done regardless
+		 * of this optimization, below).  Also, note that the cases where we
+		 * hold a lock stronger than we are requesting are already handled
+		 * above by not doing anything.
+		 *
+		 * Note we only deal with the non-multixact case here; MultiXactIdWait
+		 * is well equipped to deal with this situation on its own.
+		 */
+		if (require_sleep && !(infomask & HEAP_XMAX_IS_MULTI) &&
+			TransactionIdIsCurrentTransactionId(xwait))
+		{
+			/* ... but if the xmax changed in the meantime, start over */
+			LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+			if (xmax_infomask_changed(tuple->t_data->t_infomask, infomask) ||
+				!TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple->t_data),
+									 xwait))
+				goto l3;
+			Assert(HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_data->t_infomask));
+			require_sleep = false;
+		}
+
+		/*
+		 * Time to sleep on the other transaction/multixact, if necessary.
+		 *
+		 * If the other transaction is an update/delete that's already
+		 * committed, then sleeping cannot possibly do any good: if we're
+		 * required to sleep, get out to raise an error instead.
+		 *
+		 * By here, we either have already acquired the buffer exclusive lock,
+		 * or we must wait for the locking transaction or multixact; so below
+		 * we ensure that we grab buffer lock after the sleep.
+		 */
+		if (require_sleep && (result == TM_Updated || result == TM_Deleted))
+		{
+			LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+			goto failed;
+		}
+		else if (require_sleep)
+		{
+			/*
+			 * Acquire tuple lock to establish our priority for the tuple, or
+			 * die trying.  LockTuple will release us when we are next-in-line
+			 * for the tuple.  We must do this even if we are share-locking,
+			 * but not if we already have a weaker lock on the tuple.
+			 *
+			 * If we are forced to "start over" below, we keep the tuple lock;
+			 * this arranges that we stay at the head of the line while
+			 * rechecking tuple state.
+			 */
+			if (!skip_tuple_lock &&
+				!heap_acquire_tuplock(relation, tid, mode, wait_policy,
+									  &have_tuple_lock))
+			{
+				/*
+				 * This can only happen if wait_policy is Skip and the lock
+				 * couldn't be obtained.
+				 */
+				result = TM_WouldBlock;
+				/* recovery code expects to have buffer lock held */
+				LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+				goto failed;
+			}
+
+			if (infomask & HEAP_XMAX_IS_MULTI)
+			{
+				MultiXactStatus status = get_mxact_status_for_lock(mode, false);
+
+				/* We only ever lock tuples, never update them */
+				if (status >= MultiXactStatusNoKeyUpdate)
+					elog(ERROR, "invalid lock mode in heap_lock_tuple");
+
+				/* wait for multixact to end, or die trying  */
+				switch (wait_policy)
+				{
+					case LockWaitBlock:
+						MultiXactIdWait((MultiXactId) xwait, status, infomask,
+										relation, &tuple->t_self, XLTW_Lock, NULL);
+						break;
+					case LockWaitSkip:
+						if (!ConditionalMultiXactIdWait((MultiXactId) xwait,
+														status, infomask, relation,
+														NULL))
+						{
+							result = TM_WouldBlock;
+							/* recovery code expects to have buffer lock held */
+							LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+							goto failed;
+						}
+						break;
+					case LockWaitError:
+						if (!ConditionalMultiXactIdWait((MultiXactId) xwait,
+														status, infomask, relation,
+														NULL))
+							ereport(ERROR,
+									(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
+									 errmsg("could not obtain lock on row in relation \"%s\"",
+											RelationGetRelationName(relation))));
+
+						break;
+				}
+
+				/*
+				 * Of course, the multixact might not be done here: if we're
+				 * requesting a light lock mode, other transactions with light
+				 * locks could still be alive, as well as locks owned by our
+				 * own xact or other subxacts of this backend.  We need to
+				 * preserve the surviving MultiXact members.  Note that it
+				 * isn't absolutely necessary in the latter case, but doing so
+				 * is simpler.
+				 */
+			}
+			else
+			{
+				/* wait for regular transaction to end, or die trying */
+				switch (wait_policy)
+				{
+					case LockWaitBlock:
+						XactLockTableWait(xwait, relation, &tuple->t_self,
+										  XLTW_Lock);
+						break;
+					case LockWaitSkip:
+						if (!ConditionalXactLockTableWait(xwait))
+						{
+							result = TM_WouldBlock;
+							/* recovery code expects to have buffer lock held */
+							LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+							goto failed;
+						}
+						break;
+					case LockWaitError:
+						if (!ConditionalXactLockTableWait(xwait))
+							ereport(ERROR,
+									(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
+									 errmsg("could not obtain lock on row in relation \"%s\"",
+											RelationGetRelationName(relation))));
+						break;
+				}
+			}
+
+			/* if there are updates, follow the update chain */
+			if (follow_updates && !HEAP_XMAX_IS_LOCKED_ONLY(infomask))
+			{
+				TM_Result	res;
+
+				res = heap_lock_updated_tuple(relation, tuple, &t_ctid,
+											  GetCurrentTransactionId(),
+											  mode);
+				if (res != TM_Ok)
+				{
+					result = res;
+					/* recovery code expects to have buffer lock held */
+					LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+					goto failed;
+				}
+			}
+
+			LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+
+			/*
+			 * xwait is done, but if xwait had just locked the tuple then some
+			 * other xact could update this tuple before we get to this point.
+			 * Check for xmax change, and start over if so.
+			 */
+			if (xmax_infomask_changed(tuple->t_data->t_infomask, infomask) ||
+				!TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple->t_data),
+									 xwait))
+				goto l3;
+
+			if (!(infomask & HEAP_XMAX_IS_MULTI))
+			{
+				/*
+				 * Otherwise check if it committed or aborted.  Note we cannot
+				 * be here if the tuple was only locked by somebody who didn't
+				 * conflict with us; that would have been handled above.  So
+				 * that transaction must necessarily be gone by now.  But
+				 * don't check for this in the multixact case, because some
+				 * locker transactions might still be running.
+				 */
+				UpdateXmaxHintBits(tuple->t_data, *buffer, xwait);
+			}
+		}
+
+		/* By here, we're certain that we hold buffer exclusive lock again */
+
+		/*
+		 * We may lock if previous xmax aborted, or if it committed but only
+		 * locked the tuple without updating it; or if we didn't have to wait
+		 * at all for whatever reason.
+		 */
+		if (!require_sleep ||
+			(tuple->t_data->t_infomask & HEAP_XMAX_INVALID) ||
+			HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_data->t_infomask) ||
+			HeapTupleHeaderIsOnlyLocked(tuple->t_data))
+			result = TM_Ok;
+		else if (!ItemPointerEquals(&tuple->t_self, &tuple->t_data->t_ctid))
+			result = TM_Updated;
+		else
+			result = TM_Deleted;
+	}
+
+failed:
+	if (result != TM_Ok)
+	{
+		Assert(result == TM_SelfModified || result == TM_Updated ||
+			   result == TM_Deleted || result == TM_WouldBlock);
+
+		/*
+		 * When locking a tuple under LockWaitSkip semantics and we fail with
+		 * TM_WouldBlock above, it's possible for concurrent transactions to
+		 * release the lock and set HEAP_XMAX_INVALID in the meantime.  So
+		 * this assert is slightly different from the equivalent one in
+		 * heap_delete and heap_update.
+		 */
+		Assert((result == TM_WouldBlock) ||
+			   !(tuple->t_data->t_infomask & HEAP_XMAX_INVALID));
+		Assert(result != TM_Updated ||
+			   !ItemPointerEquals(&tuple->t_self, &tuple->t_data->t_ctid));
+		tmfd->ctid = tuple->t_data->t_ctid;
+		tmfd->xmax = HeapTupleHeaderGetUpdateXid(tuple->t_data);
+		if (result == TM_SelfModified)
+			tmfd->cmax = HeapTupleHeaderGetCmax(tuple->t_data);
+		else
+			tmfd->cmax = InvalidCommandId;
+		goto out_locked;
+	}
+
+	/*
+	 * If we didn't pin the visibility map page and the page has become all
+	 * visible while we were busy locking the buffer, or during some
+	 * subsequent window during which we had it unlocked, we'll have to unlock
+	 * and re-lock, to avoid holding the buffer lock across I/O.  That's a bit
+	 * unfortunate, especially since we'll now have to recheck whether the
+	 * tuple has been locked or updated under us, but hopefully it won't
+	 * happen very often.
+	 */
+	if (vmbuffer == InvalidBuffer && PageIsAllVisible(page))
+	{
+		LockBuffer(*buffer, BUFFER_LOCK_UNLOCK);
+		visibilitymap_pin(relation, block, &vmbuffer);
+		LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+		goto l3;
+	}
+
+	xmax = HeapTupleHeaderGetRawXmax(tuple->t_data);
+	old_infomask = tuple->t_data->t_infomask;
+
+	/*
+	 * If this is the first possibly-multixact-able operation in the current
+	 * transaction, set my per-backend OldestMemberMXactId setting. We can be
+	 * certain that the transaction will never become a member of any older
+	 * MultiXactIds than that.  (We have to do this even if we end up just
+	 * using our own TransactionId below, since some other backend could
+	 * incorporate our XID into a MultiXact immediately afterwards.)
+	 */
+	MultiXactIdSetOldestMember();
+
+	/*
+	 * Compute the new xmax and infomask to store into the tuple.  Note we do
+	 * not modify the tuple just yet, because that would leave it in the wrong
+	 * state if multixact.c elogs.
+	 */
+	compute_new_xmax_infomask(xmax, old_infomask, tuple->t_data->t_infomask2,
+							  GetCurrentTransactionId(), mode, false,
+							  &xid, &new_infomask, &new_infomask2);
+
+	START_CRIT_SECTION();
+
+	/*
+	 * Store transaction information of xact locking the tuple.
+	 *
+	 * Note: Cmax is meaningless in this context, so don't set it; this avoids
+	 * possibly generating a useless combo CID.  Moreover, if we're locking a
+	 * previously updated tuple, it's important to preserve the Cmax.
+	 *
+	 * Also reset the HOT UPDATE bit, but only if there's no update; otherwise
+	 * we would break the HOT chain.
+	 */
+	tuple->t_data->t_infomask &= ~HEAP_XMAX_BITS;
+	tuple->t_data->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+	tuple->t_data->t_infomask |= new_infomask;
+	tuple->t_data->t_infomask2 |= new_infomask2;
+	if (HEAP_XMAX_IS_LOCKED_ONLY(new_infomask))
+		HeapTupleHeaderClearHotUpdated(tuple->t_data);
+	HeapTupleHeaderSetXmax(tuple->t_data, xid);
+
+	/*
+	 * Make sure there is no forward chain link in t_ctid.  Note that in the
+	 * cases where the tuple has been updated, we must not overwrite t_ctid,
+	 * because it was set by the updater.  Moreover, if the tuple has been
+	 * updated, we need to follow the update chain to lock the new versions of
+	 * the tuple as well.
+	 */
+	if (HEAP_XMAX_IS_LOCKED_ONLY(new_infomask))
+		tuple->t_data->t_ctid = *tid;
+
+	/* Clear only the all-frozen bit on visibility map if needed */
+	if (PageIsAllVisible(page) &&
+		visibilitymap_clear(relation, block, vmbuffer,
+							VISIBILITYMAP_ALL_FROZEN))
+		cleared_all_frozen = true;
+
+
+	MarkBufferDirty(*buffer);
+
+	/*
+	 * XLOG stuff.  You might think that we don't need an XLOG record because
+	 * there is no state change worth restoring after a crash.  You would be
+	 * wrong however: we have just written either a TransactionId or a
+	 * MultiXactId that may never have been seen on disk before, and we need
+	 * to make sure that there are XLOG entries covering those ID numbers.
+	 * Else the same IDs might be re-used after a crash, which would be
+	 * disastrous if this page made it to disk before the crash.  Essentially
+	 * we have to enforce the WAL log-before-data rule even in this case.
+	 * (Also, in a PITR log-shipping or 2PC environment, we have to have XLOG
+	 * entries for everything anyway.)
+	 */
+	if (RelationNeedsWAL(relation))
+	{
+		xl_heap_lock xlrec;
+		XLogRecPtr	recptr;
+
+		XLogBeginInsert();
+		XLogRegisterBuffer(0, *buffer, REGBUF_STANDARD);
+
+		xlrec.offnum = ItemPointerGetOffsetNumber(&tuple->t_self);
+		xlrec.locking_xid = xid;
+		xlrec.infobits_set = compute_infobits(new_infomask,
+											  tuple->t_data->t_infomask2);
+		xlrec.flags = cleared_all_frozen ? XLH_LOCK_ALL_FROZEN_CLEARED : 0;
+		XLogRegisterData((char *) &xlrec, SizeOfHeapLock);
+
+		/* we don't decode row locks atm, so no need to log the origin */
+
+		recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_LOCK);
+
+		PageSetLSN(page, recptr);
+	}
+
+	END_CRIT_SECTION();
+
+	result = TM_Ok;
+
+out_locked:
+	LockBuffer(*buffer, BUFFER_LOCK_UNLOCK);
+
+out_unlocked:
+	if (BufferIsValid(vmbuffer))
+		ReleaseBuffer(vmbuffer);
+
+	/*
+	 * Don't update the visibility map here. Locking a tuple doesn't change
+	 * visibility info.
+	 */
+
+	/*
+	 * Now that we have successfully marked the tuple as locked, we can
+	 * release the lmgr tuple lock, if we had it.
+	 */
+	if (have_tuple_lock)
+		UnlockTupleTuplock(relation, tid, mode);
+
+	return result;
+}
+
+/*
+ * Acquire heavyweight lock on the given tuple, in preparation for acquiring
+ * its normal, Xmax-based tuple lock.
+ *
+ * have_tuple_lock is an input and output parameter: on input, it indicates
+ * whether the lock has previously been acquired (and this function does
+ * nothing in that case).  If this function returns success, have_tuple_lock
+ * has been flipped to true.
+ *
+ * Returns false if it was unable to obtain the lock; this can only happen if
+ * wait_policy is Skip.
+ */
+static bool
+heap_acquire_tuplock(Relation relation, ItemPointer tid, LockTupleMode mode,
+					 LockWaitPolicy wait_policy, bool *have_tuple_lock)
+{
+	if (*have_tuple_lock)
+		return true;
+
+	switch (wait_policy)
+	{
+		case LockWaitBlock:
+			LockTupleTuplock(relation, tid, mode);
+			break;
+
+		case LockWaitSkip:
+			if (!ConditionalLockTupleTuplock(relation, tid, mode))
+				return false;
+			break;
+
+		case LockWaitError:
+			if (!ConditionalLockTupleTuplock(relation, tid, mode))
+				ereport(ERROR,
+						(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
+						 errmsg("could not obtain lock on row in relation \"%s\"",
+								RelationGetRelationName(relation))));
+			break;
+	}
+	*have_tuple_lock = true;
+
+	return true;
+}
+
+/*
+ * Given an original set of Xmax and infomask, and a transaction (identified by
+ * add_to_xmax) acquiring a new lock of some mode, compute the new Xmax and
+ * corresponding infomasks to use on the tuple.
+ *
+ * Note that this might have side effects such as creating a new MultiXactId.
+ *
+ * Most callers will have called HeapTupleSatisfiesUpdate before this function;
+ * that will have set the HEAP_XMAX_INVALID bit if the xmax was a MultiXactId
+ * but it was not running anymore. There is a race condition, which is that the
+ * MultiXactId may have finished since then, but that uncommon case is handled
+ * either here, or within MultiXactIdExpand.
+ *
+ * There is a similar race condition possible when the old xmax was a regular
+ * TransactionId.  We test TransactionIdIsInProgress again just to narrow the
+ * window, but it's still possible to end up creating an unnecessary
+ * MultiXactId.  Fortunately this is harmless.
+ */
+static void
+compute_new_xmax_infomask(TransactionId xmax, uint16 old_infomask,
+						  uint16 old_infomask2, TransactionId add_to_xmax,
+						  LockTupleMode mode, bool is_update,
+						  TransactionId *result_xmax, uint16 *result_infomask,
+						  uint16 *result_infomask2)
+{
+	TransactionId new_xmax;
+	uint16		new_infomask,
+				new_infomask2;
+
+	Assert(TransactionIdIsCurrentTransactionId(add_to_xmax));
+
+l5:
+	new_infomask = 0;
+	new_infomask2 = 0;
+	if (old_infomask & HEAP_XMAX_INVALID)
+	{
+		/*
+		 * No previous locker; we just insert our own TransactionId.
+		 *
+		 * Note that it's critical that this case be the first one checked,
+		 * because there are several blocks below that come back to this one
+		 * to implement certain optimizations; old_infomask might contain
+		 * other dirty bits in those cases, but we don't really care.
+		 */
+		if (is_update)
+		{
+			new_xmax = add_to_xmax;
+			if (mode == LockTupleExclusive)
+				new_infomask2 |= HEAP_KEYS_UPDATED;
+		}
+		else
+		{
+			new_infomask |= HEAP_XMAX_LOCK_ONLY;
+			switch (mode)
+			{
+				case LockTupleKeyShare:
+					new_xmax = add_to_xmax;
+					new_infomask |= HEAP_XMAX_KEYSHR_LOCK;
+					break;
+				case LockTupleShare:
+					new_xmax = add_to_xmax;
+					new_infomask |= HEAP_XMAX_SHR_LOCK;
+					break;
+				case LockTupleNoKeyExclusive:
+					new_xmax = add_to_xmax;
+					new_infomask |= HEAP_XMAX_EXCL_LOCK;
+					break;
+				case LockTupleExclusive:
+					new_xmax = add_to_xmax;
+					new_infomask |= HEAP_XMAX_EXCL_LOCK;
+					new_infomask2 |= HEAP_KEYS_UPDATED;
+					break;
+				default:
+					new_xmax = InvalidTransactionId;	/* silence compiler */
+					elog(ERROR, "invalid lock mode");
+			}
+		}
+	}
+	else if (old_infomask & HEAP_XMAX_IS_MULTI)
+	{
+		MultiXactStatus new_status;
+
+		/*
+		 * Currently we don't allow XMAX_COMMITTED to be set for multis, so
+		 * cross-check.
+		 */
+		Assert(!(old_infomask & HEAP_XMAX_COMMITTED));
+
+		/*
+		 * A multixact together with LOCK_ONLY set but neither lock bit set
+		 * (i.e. a pg_upgraded share locked tuple) cannot possibly be running
+		 * anymore.  This check is critical for databases upgraded by
+		 * pg_upgrade; both MultiXactIdIsRunning and MultiXactIdExpand assume
+		 * that such multis are never passed.
+		 */
+		if (HEAP_LOCKED_UPGRADED(old_infomask))
+		{
+			old_infomask &= ~HEAP_XMAX_IS_MULTI;
+			old_infomask |= HEAP_XMAX_INVALID;
+			goto l5;
+		}
+
+		/*
+		 * If the XMAX is already a MultiXactId, then we need to expand it to
+		 * include add_to_xmax; but if all the members were lockers and are
+		 * all gone, we can do away with the IS_MULTI bit and just set
+		 * add_to_xmax as the only locker/updater.  If all lockers are gone
+		 * and we have an updater that aborted, we can also do without a
+		 * multi.
+		 *
+		 * The cost of doing GetMultiXactIdMembers would be paid by
+		 * MultiXactIdExpand if we weren't to do this, so this check is not
+		 * incurring extra work anyhow.
+		 */
+		if (!MultiXactIdIsRunning(xmax, HEAP_XMAX_IS_LOCKED_ONLY(old_infomask)))
+		{
+			if (HEAP_XMAX_IS_LOCKED_ONLY(old_infomask) ||
+				!TransactionIdDidCommit(MultiXactIdGetUpdateXid(xmax,
+																old_infomask)))
+			{
+				/*
+				 * Reset these bits and restart; otherwise fall through to
+				 * create a new multi below.
+				 */
+				old_infomask &= ~HEAP_XMAX_IS_MULTI;
+				old_infomask |= HEAP_XMAX_INVALID;
+				goto l5;
+			}
+		}
+
+		new_status = get_mxact_status_for_lock(mode, is_update);
+
+		new_xmax = MultiXactIdExpand((MultiXactId) xmax, add_to_xmax,
+									 new_status);
+		GetMultiXactIdHintBits(new_xmax, &new_infomask, &new_infomask2);
+	}
+	else if (old_infomask & HEAP_XMAX_COMMITTED)
+	{
+		/*
+		 * It's a committed update, so we need to preserve him as updater of
+		 * the tuple.
+		 */
+		MultiXactStatus status;
+		MultiXactStatus new_status;
+
+		if (old_infomask2 & HEAP_KEYS_UPDATED)
+			status = MultiXactStatusUpdate;
+		else
+			status = MultiXactStatusNoKeyUpdate;
+
+		new_status = get_mxact_status_for_lock(mode, is_update);
+
+		/*
+		 * since it's not running, it's obviously impossible for the old
+		 * updater to be identical to the current one, so we need not check
+		 * for that case as we do in the block above.
+		 */
+		new_xmax = MultiXactIdCreate(xmax, status, add_to_xmax, new_status);
+		GetMultiXactIdHintBits(new_xmax, &new_infomask, &new_infomask2);
+	}
+	else if (TransactionIdIsInProgress(xmax))
+	{
+		/*
+		 * If the XMAX is a valid, in-progress TransactionId, then we need to
+		 * create a new MultiXactId that includes both the old locker or
+		 * updater and our own TransactionId.
+		 */
+		MultiXactStatus new_status;
+		MultiXactStatus old_status;
+		LockTupleMode old_mode;
+
+		if (HEAP_XMAX_IS_LOCKED_ONLY(old_infomask))
+		{
+			if (HEAP_XMAX_IS_KEYSHR_LOCKED(old_infomask))
+				old_status = MultiXactStatusForKeyShare;
+			else if (HEAP_XMAX_IS_SHR_LOCKED(old_infomask))
+				old_status = MultiXactStatusForShare;
+			else if (HEAP_XMAX_IS_EXCL_LOCKED(old_infomask))
+			{
+				if (old_infomask2 & HEAP_KEYS_UPDATED)
+					old_status = MultiXactStatusForUpdate;
+				else
+					old_status = MultiXactStatusForNoKeyUpdate;
+			}
+			else
+			{
+				/*
+				 * LOCK_ONLY can be present alone only when a page has been
+				 * upgraded by pg_upgrade.  But in that case,
+				 * TransactionIdIsInProgress() should have returned false.  We
+				 * assume it's no longer locked in this case.
+				 */
+				elog(WARNING, "LOCK_ONLY found for Xid in progress %u", xmax);
+				old_infomask |= HEAP_XMAX_INVALID;
+				old_infomask &= ~HEAP_XMAX_LOCK_ONLY;
+				goto l5;
+			}
+		}
+		else
+		{
+			/* it's an update, but which kind? */
+			if (old_infomask2 & HEAP_KEYS_UPDATED)
+				old_status = MultiXactStatusUpdate;
+			else
+				old_status = MultiXactStatusNoKeyUpdate;
+		}
+
+		old_mode = TUPLOCK_from_mxstatus(old_status);
+
+		/*
+		 * If the lock to be acquired is for the same TransactionId as the
+		 * existing lock, there's an optimization possible: consider only the
+		 * strongest of both locks as the only one present, and restart.
+		 */
+		if (xmax == add_to_xmax)
+		{
+			/*
+			 * Note that it's not possible for the original tuple to be
+			 * updated: we wouldn't be here because the tuple would have been
+			 * invisible and we wouldn't try to update it.  As a subtlety,
+			 * this code can also run when traversing an update chain to lock
+			 * future versions of a tuple.  But we wouldn't be here either,
+			 * because the add_to_xmax would be different from the original
+			 * updater.
+			 */
+			Assert(HEAP_XMAX_IS_LOCKED_ONLY(old_infomask));
+
+			/* acquire the strongest of both */
+			if (mode < old_mode)
+				mode = old_mode;
+			/* mustn't touch is_update */
+
+			old_infomask |= HEAP_XMAX_INVALID;
+			goto l5;
+		}
+
+		/* otherwise, just fall back to creating a new multixact */
+		new_status = get_mxact_status_for_lock(mode, is_update);
+		new_xmax = MultiXactIdCreate(xmax, old_status,
+									 add_to_xmax, new_status);
+		GetMultiXactIdHintBits(new_xmax, &new_infomask, &new_infomask2);
+	}
+	else if (!HEAP_XMAX_IS_LOCKED_ONLY(old_infomask) &&
+			 TransactionIdDidCommit(xmax))
+	{
+		/*
+		 * It's a committed update, so we gotta preserve him as updater of the
+		 * tuple.
+		 */
+		MultiXactStatus status;
+		MultiXactStatus new_status;
+
+		if (old_infomask2 & HEAP_KEYS_UPDATED)
+			status = MultiXactStatusUpdate;
+		else
+			status = MultiXactStatusNoKeyUpdate;
+
+		new_status = get_mxact_status_for_lock(mode, is_update);
+
+		/*
+		 * since it's not running, it's obviously impossible for the old
+		 * updater to be identical to the current one, so we need not check
+		 * for that case as we do in the block above.
+		 */
+		new_xmax = MultiXactIdCreate(xmax, status, add_to_xmax, new_status);
+		GetMultiXactIdHintBits(new_xmax, &new_infomask, &new_infomask2);
+	}
+	else
+	{
+		/*
+		 * Can get here iff the locking/updating transaction was running when
+		 * the infomask was extracted from the tuple, but finished before
+		 * TransactionIdIsInProgress got to run.  Deal with it as if there was
+		 * no locker at all in the first place.
+		 */
+		old_infomask |= HEAP_XMAX_INVALID;
+		goto l5;
+	}
+
+	*result_infomask = new_infomask;
+	*result_infomask2 = new_infomask2;
+	*result_xmax = new_xmax;
+}
+
+/*
+ * Subroutine for heap_lock_updated_tuple_rec.
+ *
+ * Given a hypothetical multixact status held by the transaction identified
+ * with the given xid, does the current transaction need to wait, fail, or can
+ * it continue if it wanted to acquire a lock of the given mode?  "needwait"
+ * is set to true if waiting is necessary; if it can continue, then TM_Ok is
+ * returned.  If the lock is already held by the current transaction, return
+ * TM_SelfModified.  In case of a conflict with another transaction, a
+ * different HeapTupleSatisfiesUpdate return code is returned.
+ *
+ * The held status is said to be hypothetical because it might correspond to a
+ * lock held by a single Xid, i.e. not a real MultiXactId; we express it this
+ * way for simplicity of API.
+ */
+static TM_Result
+test_lockmode_for_conflict(MultiXactStatus status, TransactionId xid,
+						   LockTupleMode mode, HeapTuple tup,
+						   bool *needwait)
+{
+	MultiXactStatus wantedstatus;
+
+	*needwait = false;
+	wantedstatus = get_mxact_status_for_lock(mode, false);
+
+	/*
+	 * Note: we *must* check TransactionIdIsInProgress before
+	 * TransactionIdDidAbort/Commit; see comment at top of heapam_visibility.c
+	 * for an explanation.
+	 */
+	if (TransactionIdIsCurrentTransactionId(xid))
+	{
+		/*
+		 * The tuple has already been locked by our own transaction.  This is
+		 * very rare but can happen if multiple transactions are trying to
+		 * lock an ancient version of the same tuple.
+		 */
+		return TM_SelfModified;
+	}
+	else if (TransactionIdIsInProgress(xid))
+	{
+		/*
+		 * If the locking transaction is running, what we do depends on
+		 * whether the lock modes conflict: if they do, then we must wait for
+		 * it to finish; otherwise we can fall through to lock this tuple
+		 * version without waiting.
+		 */
+		if (DoLockModesConflict(LOCKMODE_from_mxstatus(status),
+								LOCKMODE_from_mxstatus(wantedstatus)))
+		{
+			*needwait = true;
+		}
+
+		/*
+		 * If we set needwait above, then this value doesn't matter;
+		 * otherwise, this value signals to caller that it's okay to proceed.
+		 */
+		return TM_Ok;
+	}
+	else if (TransactionIdDidAbort(xid))
+		return TM_Ok;
+	else if (TransactionIdDidCommit(xid))
+	{
+		/*
+		 * The other transaction committed.  If it was only a locker, then the
+		 * lock is completely gone now and we can return success; but if it
+		 * was an update, then what we do depends on whether the two lock
+		 * modes conflict.  If they conflict, then we must report error to
+		 * caller. But if they don't, we can fall through to allow the current
+		 * transaction to lock the tuple.
+		 *
+		 * Note: the reason we worry about ISUPDATE here is because as soon as
+		 * a transaction ends, all its locks are gone and meaningless, and
+		 * thus we can ignore them; whereas its updates persist.  In the
+		 * TransactionIdIsInProgress case, above, we don't need to check
+		 * because we know the lock is still "alive" and thus a conflict needs
+		 * always be checked.
+		 */
+		if (!ISUPDATE_from_mxstatus(status))
+			return TM_Ok;
+
+		if (DoLockModesConflict(LOCKMODE_from_mxstatus(status),
+								LOCKMODE_from_mxstatus(wantedstatus)))
+		{
+			/* bummer */
+			if (!ItemPointerEquals(&tup->t_self, &tup->t_data->t_ctid))
+				return TM_Updated;
+			else
+				return TM_Deleted;
+		}
+
+		return TM_Ok;
+	}
+
+	/* Not in progress, not aborted, not committed -- must have crashed */
+	return TM_Ok;
+}
+
+
+/*
+ * Recursive part of heap_lock_updated_tuple
+ *
+ * Fetch the tuple pointed to by tid in rel, and mark it as locked by the given
+ * xid with the given mode; if this tuple is updated, recurse to lock the new
+ * version as well.
+ */
+static TM_Result
+heap_lock_updated_tuple_rec(Relation rel, ItemPointer tid, TransactionId xid,
+							LockTupleMode mode)
+{
+	TM_Result	result;
+	ItemPointerData tupid;
+	HeapTupleData mytup;
+	Buffer		buf;
+	uint16		new_infomask,
+				new_infomask2,
+				old_infomask,
+				old_infomask2;
+	TransactionId xmax,
+				new_xmax;
+	TransactionId priorXmax = InvalidTransactionId;
+	bool		cleared_all_frozen = false;
+	bool		pinned_desired_page;
+	Buffer		vmbuffer = InvalidBuffer;
+	BlockNumber block;
+
+	ItemPointerCopy(tid, &tupid);
+
+	for (;;)
+	{
+		new_infomask = 0;
+		new_xmax = InvalidTransactionId;
+		block = ItemPointerGetBlockNumber(&tupid);
+		ItemPointerCopy(&tupid, &(mytup.t_self));
+
+		if (!heap_fetch(rel, SnapshotAny, &mytup, &buf, false))
+		{
+			/*
+			 * if we fail to find the updated version of the tuple, it's
+			 * because it was vacuumed/pruned away after its creator
+			 * transaction aborted.  So behave as if we got to the end of the
+			 * chain, and there's no further tuple to lock: return success to
+			 * caller.
+			 */
+			result = TM_Ok;
+			goto out_unlocked;
+		}
+
+l4:
+		CHECK_FOR_INTERRUPTS();
+
+		/*
+		 * Before locking the buffer, pin the visibility map page if it
+		 * appears to be necessary.  Since we haven't got the lock yet,
+		 * someone else might be in the middle of changing this, so we'll need
+		 * to recheck after we have the lock.
+		 */
+		if (PageIsAllVisible(BufferGetPage(buf)))
+		{
+			visibilitymap_pin(rel, block, &vmbuffer);
+			pinned_desired_page = true;
+		}
+		else
+			pinned_desired_page = false;
+
+		LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
+
+		/*
+		 * If we didn't pin the visibility map page and the page has become
+		 * all visible while we were busy locking the buffer, we'll have to
+		 * unlock and re-lock, to avoid holding the buffer lock across I/O.
+		 * That's a bit unfortunate, but hopefully shouldn't happen often.
+		 *
+		 * Note: in some paths through this function, we will reach here
+		 * holding a pin on a vm page that may or may not be the one matching
+		 * this page.  If this page isn't all-visible, we won't use the vm
+		 * page, but we hold onto such a pin till the end of the function.
+		 */
+		if (!pinned_desired_page && PageIsAllVisible(BufferGetPage(buf)))
+		{
+			LockBuffer(buf, BUFFER_LOCK_UNLOCK);
+			visibilitymap_pin(rel, block, &vmbuffer);
+			LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
+		}
+
+		/*
+		 * Check the tuple XMIN against prior XMAX, if any.  If we reached the
+		 * end of the chain, we're done, so return success.
+		 */
+		if (TransactionIdIsValid(priorXmax) &&
+			!TransactionIdEquals(HeapTupleHeaderGetXmin(mytup.t_data),
+								 priorXmax))
+		{
+			result = TM_Ok;
+			goto out_locked;
+		}
+
+		/*
+		 * Also check Xmin: if this tuple was created by an aborted
+		 * (sub)transaction, then we already locked the last live one in the
+		 * chain, thus we're done, so return success.
+		 */
+		if (TransactionIdDidAbort(HeapTupleHeaderGetXmin(mytup.t_data)))
+		{
+			result = TM_Ok;
+			goto out_locked;
+		}
+
+		old_infomask = mytup.t_data->t_infomask;
+		old_infomask2 = mytup.t_data->t_infomask2;
+		xmax = HeapTupleHeaderGetRawXmax(mytup.t_data);
+
+		/*
+		 * If this tuple version has been updated or locked by some concurrent
+		 * transaction(s), what we do depends on whether our lock mode
+		 * conflicts with what those other transactions hold, and also on the
+		 * status of them.
+		 */
+		if (!(old_infomask & HEAP_XMAX_INVALID))
+		{
+			TransactionId rawxmax;
+			bool		needwait;
+
+			rawxmax = HeapTupleHeaderGetRawXmax(mytup.t_data);
+			if (old_infomask & HEAP_XMAX_IS_MULTI)
+			{
+				int			nmembers;
+				int			i;
+				MultiXactMember *members;
+
+				/*
+				 * We don't need a test for pg_upgrade'd tuples: this is only
+				 * applied to tuples after the first in an update chain.  Said
+				 * first tuple in the chain may well be locked-in-9.2-and-
+				 * pg_upgraded, but that one was already locked by our caller,
+				 * not us; and any subsequent ones cannot be because our
+				 * caller must necessarily have obtained a snapshot later than
+				 * the pg_upgrade itself.
+				 */
+				Assert(!HEAP_LOCKED_UPGRADED(mytup.t_data->t_infomask));
+
+				nmembers = GetMultiXactIdMembers(rawxmax, &members, false,
+												 HEAP_XMAX_IS_LOCKED_ONLY(old_infomask));
+				for (i = 0; i < nmembers; i++)
+				{
+					result = test_lockmode_for_conflict(members[i].status,
+														members[i].xid,
+														mode,
+														&mytup,
+														&needwait);
+
+					/*
+					 * If the tuple was already locked by ourselves in a
+					 * previous iteration of this (say heap_lock_tuple was
+					 * forced to restart the locking loop because of a change
+					 * in xmax), then we hold the lock already on this tuple
+					 * version and we don't need to do anything; and this is
+					 * not an error condition either.  We just need to skip
+					 * this tuple and continue locking the next version in the
+					 * update chain.
+					 */
+					if (result == TM_SelfModified)
+					{
+						pfree(members);
+						goto next;
+					}
+
+					if (needwait)
+					{
+						LockBuffer(buf, BUFFER_LOCK_UNLOCK);
+						XactLockTableWait(members[i].xid, rel,
+										  &mytup.t_self,
+										  XLTW_LockUpdated);
+						pfree(members);
+						goto l4;
+					}
+					if (result != TM_Ok)
+					{
+						pfree(members);
+						goto out_locked;
+					}
+				}
+				if (members)
+					pfree(members);
+			}
+			else
+			{
+				MultiXactStatus status;
+
+				/*
+				 * For a non-multi Xmax, we first need to compute the
+				 * corresponding MultiXactStatus by using the infomask bits.
+				 */
+				if (HEAP_XMAX_IS_LOCKED_ONLY(old_infomask))
+				{
+					if (HEAP_XMAX_IS_KEYSHR_LOCKED(old_infomask))
+						status = MultiXactStatusForKeyShare;
+					else if (HEAP_XMAX_IS_SHR_LOCKED(old_infomask))
+						status = MultiXactStatusForShare;
+					else if (HEAP_XMAX_IS_EXCL_LOCKED(old_infomask))
+					{
+						if (old_infomask2 & HEAP_KEYS_UPDATED)
+							status = MultiXactStatusForUpdate;
+						else
+							status = MultiXactStatusForNoKeyUpdate;
+					}
+					else
+					{
+						/*
+						 * LOCK_ONLY present alone (a pg_upgraded tuple marked
+						 * as share-locked in the old cluster) shouldn't be
+						 * seen in the middle of an update chain.
+						 */
+						elog(ERROR, "invalid lock status in tuple");
+					}
+				}
+				else
+				{
+					/* it's an update, but which kind? */
+					if (old_infomask2 & HEAP_KEYS_UPDATED)
+						status = MultiXactStatusUpdate;
+					else
+						status = MultiXactStatusNoKeyUpdate;
+				}
+
+				result = test_lockmode_for_conflict(status, rawxmax, mode,
+													&mytup, &needwait);
+
+				/*
+				 * If the tuple was already locked by ourselves in a previous
+				 * iteration of this (say heap_lock_tuple was forced to
+				 * restart the locking loop because of a change in xmax), then
+				 * we hold the lock already on this tuple version and we don't
+				 * need to do anything; and this is not an error condition
+				 * either.  We just need to skip this tuple and continue
+				 * locking the next version in the update chain.
+				 */
+				if (result == TM_SelfModified)
+					goto next;
+
+				if (needwait)
+				{
+					LockBuffer(buf, BUFFER_LOCK_UNLOCK);
+					XactLockTableWait(rawxmax, rel, &mytup.t_self,
+									  XLTW_LockUpdated);
+					goto l4;
+				}
+				if (result != TM_Ok)
+				{
+					goto out_locked;
+				}
+			}
+		}
+
+		/* compute the new Xmax and infomask values for the tuple ... */
+		compute_new_xmax_infomask(xmax, old_infomask, mytup.t_data->t_infomask2,
+								  xid, mode, false,
+								  &new_xmax, &new_infomask, &new_infomask2);
+
+		if (PageIsAllVisible(BufferGetPage(buf)) &&
+			visibilitymap_clear(rel, block, vmbuffer,
+								VISIBILITYMAP_ALL_FROZEN))
+			cleared_all_frozen = true;
+
+		START_CRIT_SECTION();
+
+		/* ... and set them */
+		HeapTupleHeaderSetXmax(mytup.t_data, new_xmax);
+		mytup.t_data->t_infomask &= ~HEAP_XMAX_BITS;
+		mytup.t_data->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+		mytup.t_data->t_infomask |= new_infomask;
+		mytup.t_data->t_infomask2 |= new_infomask2;
+
+		MarkBufferDirty(buf);
+
+		/* XLOG stuff */
+		if (RelationNeedsWAL(rel))
+		{
+			xl_heap_lock_updated xlrec;
+			XLogRecPtr	recptr;
+			Page		page = BufferGetPage(buf);
+
+			XLogBeginInsert();
+			XLogRegisterBuffer(0, buf, REGBUF_STANDARD);
+
+			xlrec.offnum = ItemPointerGetOffsetNumber(&mytup.t_self);
+			xlrec.xmax = new_xmax;
+			xlrec.infobits_set = compute_infobits(new_infomask, new_infomask2);
+			xlrec.flags =
+				cleared_all_frozen ? XLH_LOCK_ALL_FROZEN_CLEARED : 0;
+
+			XLogRegisterData((char *) &xlrec, SizeOfHeapLockUpdated);
+
+			recptr = XLogInsert(RM_HEAP2_ID, XLOG_HEAP2_LOCK_UPDATED);
+
+			PageSetLSN(page, recptr);
+		}
+
+		END_CRIT_SECTION();
+
+next:
+		/* if we find the end of update chain, we're done. */
+		if (mytup.t_data->t_infomask & HEAP_XMAX_INVALID ||
+			HeapTupleHeaderIndicatesMovedPartitions(mytup.t_data) ||
+			ItemPointerEquals(&mytup.t_self, &mytup.t_data->t_ctid) ||
+			HeapTupleHeaderIsOnlyLocked(mytup.t_data))
+		{
+			result = TM_Ok;
+			goto out_locked;
+		}
+
+		/* tail recursion */
+		priorXmax = HeapTupleHeaderGetUpdateXid(mytup.t_data);
+		ItemPointerCopy(&(mytup.t_data->t_ctid), &tupid);
+		UnlockReleaseBuffer(buf);
+	}
+
+	result = TM_Ok;
+
+out_locked:
+	UnlockReleaseBuffer(buf);
+
+out_unlocked:
+	if (vmbuffer != InvalidBuffer)
+		ReleaseBuffer(vmbuffer);
+
+	return result;
+}
+
+/*
+ * heap_lock_updated_tuple
+ *		Follow update chain when locking an updated tuple, acquiring locks (row
+ *		marks) on the updated versions.
+ *
+ * The initial tuple is assumed to be already locked.
+ *
+ * This function doesn't check visibility, it just unconditionally marks the
+ * tuple(s) as locked.  If any tuple in the updated chain is being deleted
+ * concurrently (or updated with the key being modified), sleep until the
+ * transaction doing it is finished.
+ *
+ * Note that we don't acquire heavyweight tuple locks on the tuples we walk
+ * when we have to wait for other transactions to release them, as opposed to
+ * what heap_lock_tuple does.  The reason is that having more than one
+ * transaction walking the chain is probably uncommon enough that risk of
+ * starvation is not likely: one of the preconditions for being here is that
+ * the snapshot in use predates the update that created this tuple (because we
+ * started at an earlier version of the tuple), but at the same time such a
+ * transaction cannot be using repeatable read or serializable isolation
+ * levels, because that would lead to a serializability failure.
+ */
+static TM_Result
+heap_lock_updated_tuple(Relation rel, HeapTuple tuple, ItemPointer ctid,
+						TransactionId xid, LockTupleMode mode)
+{
+	/*
+	 * If the tuple has not been updated, or has moved into another partition
+	 * (effectively a delete) stop here.
+	 */
+	if (!HeapTupleHeaderIndicatesMovedPartitions(tuple->t_data) &&
+		!ItemPointerEquals(&tuple->t_self, ctid))
+	{
+		/*
+		 * If this is the first possibly-multixact-able operation in the
+		 * current transaction, set my per-backend OldestMemberMXactId
+		 * setting. We can be certain that the transaction will never become a
+		 * member of any older MultiXactIds than that.  (We have to do this
+		 * even if we end up just using our own TransactionId below, since
+		 * some other backend could incorporate our XID into a MultiXact
+		 * immediately afterwards.)
+		 */
+		MultiXactIdSetOldestMember();
+
+		return heap_lock_updated_tuple_rec(rel, ctid, xid, mode);
+	}
+
+	/* nothing to lock */
+	return TM_Ok;
+}
+
+/*
+ *	heap_finish_speculative - mark speculative insertion as successful
+ *
+ * To successfully finish a speculative insertion we have to clear speculative
+ * token from tuple.  To do so the t_ctid field, which will contain a
+ * speculative token value, is modified in place to point to the tuple itself,
+ * which is characteristic of a newly inserted ordinary tuple.
+ *
+ * NB: It is not ok to commit without either finishing or aborting a
+ * speculative insertion.  We could treat speculative tuples of committed
+ * transactions implicitly as completed, but then we would have to be prepared
+ * to deal with speculative tokens on committed tuples.  That wouldn't be
+ * difficult - no-one looks at the ctid field of a tuple with invalid xmax -
+ * but clearing the token at completion isn't very expensive either.
+ * An explicit confirmation WAL record also makes logical decoding simpler.
+ */
+void
+heap_finish_speculative(Relation relation, ItemPointer tid)
+{
+	Buffer		buffer;
+	Page		page;
+	OffsetNumber offnum;
+	ItemId		lp = NULL;
+	HeapTupleHeader htup;
+
+	buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));
+	LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+	page = (Page) BufferGetPage(buffer);
+
+	offnum = ItemPointerGetOffsetNumber(tid);
+	if (PageGetMaxOffsetNumber(page) >= offnum)
+		lp = PageGetItemId(page, offnum);
+
+	if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp))
+		elog(ERROR, "invalid lp");
+
+	htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+	/* SpecTokenOffsetNumber should be distinguishable from any real offset */
+	StaticAssertStmt(MaxOffsetNumber < SpecTokenOffsetNumber,
+					 "invalid speculative token constant");
+
+	/* NO EREPORT(ERROR) from here till changes are logged */
+	START_CRIT_SECTION();
+
+	Assert(HeapTupleHeaderIsSpeculative(htup));
+
+	MarkBufferDirty(buffer);
+
+	/*
+	 * Replace the speculative insertion token with a real t_ctid, pointing to
+	 * itself like it does on regular tuples.
+	 */
+	htup->t_ctid = *tid;
+
+	/* XLOG stuff */
+	if (RelationNeedsWAL(relation))
+	{
+		xl_heap_confirm xlrec;
+		XLogRecPtr	recptr;
+
+		xlrec.offnum = ItemPointerGetOffsetNumber(tid);
+
+		XLogBeginInsert();
+
+		/* We want the same filtering on this as on a plain insert */
+		XLogSetRecordFlags(XLOG_INCLUDE_ORIGIN);
+
+		XLogRegisterData((char *) &xlrec, SizeOfHeapConfirm);
+		XLogRegisterBuffer(0, buffer, REGBUF_STANDARD);
+
+		recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_CONFIRM);
+
+		PageSetLSN(page, recptr);
+	}
+
+	END_CRIT_SECTION();
+
+	UnlockReleaseBuffer(buffer);
+}
+
+/*
+ *	heap_abort_speculative - kill a speculatively inserted tuple
+ *
+ * Marks a tuple that was speculatively inserted in the same command as dead,
+ * by setting its xmin as invalid.  That makes it immediately appear as dead
+ * to all transactions, including our own.  In particular, it makes
+ * HeapTupleSatisfiesDirty() regard the tuple as dead, so that another backend
+ * inserting a duplicate key value won't unnecessarily wait for our whole
+ * transaction to finish (it'll just wait for our speculative insertion to
+ * finish).
+ *
+ * Killing the tuple prevents "unprincipled deadlocks", which are deadlocks
+ * that arise due to a mutual dependency that is not user visible.  By
+ * definition, unprincipled deadlocks cannot be prevented by the user
+ * reordering lock acquisition in client code, because the implementation level
+ * lock acquisitions are not under the user's direct control.  If speculative
+ * inserters did not take this precaution, then under high concurrency they
+ * could deadlock with each other, which would not be acceptable.
+ *
+ * This is somewhat redundant with heap_delete, but we prefer to have a
+ * dedicated routine with stripped down requirements.  Note that this is also
+ * used to delete the TOAST tuples created during speculative insertion.
+ *
+ * This routine does not affect logical decoding as it only looks at
+ * confirmation records.
+ */
+void
+heap_abort_speculative(Relation relation, ItemPointer tid)
+{
+	TransactionId xid = GetCurrentTransactionId();
+	ItemId		lp;
+	HeapTupleData tp;
+	Page		page;
+	BlockNumber block;
+	Buffer		buffer;
+	TransactionId prune_xid;
+
+	Assert(ItemPointerIsValid(tid));
+
+	block = ItemPointerGetBlockNumber(tid);
+	buffer = ReadBuffer(relation, block);
+	page = BufferGetPage(buffer);
+
+	LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+
+	/*
+	 * Page can't be all visible, we just inserted into it, and are still
+	 * running.
+	 */
+	Assert(!PageIsAllVisible(page));
+
+	lp = PageGetItemId(page, ItemPointerGetOffsetNumber(tid));
+	Assert(ItemIdIsNormal(lp));
+
+	tp.t_tableOid = RelationGetRelid(relation);
+	tp.t_data = (HeapTupleHeader) PageGetItem(page, lp);
+	tp.t_len = ItemIdGetLength(lp);
+	tp.t_self = *tid;
+
+	/*
+	 * Sanity check that the tuple really is a speculatively inserted tuple,
+	 * inserted by us.
+	 */
+	if (tp.t_data->t_choice.t_heap.t_xmin != xid)
+		elog(ERROR, "attempted to kill a tuple inserted by another transaction");
+	if (!(IsToastRelation(relation) || HeapTupleHeaderIsSpeculative(tp.t_data)))
+		elog(ERROR, "attempted to kill a non-speculative tuple");
+	Assert(!HeapTupleHeaderIsHeapOnly(tp.t_data));
+
+	/*
+	 * No need to check for serializable conflicts here.  There is never a
+	 * need for a combo CID, either.  No need to extract replica identity, or
+	 * do anything special with infomask bits.
+	 */
+
+	START_CRIT_SECTION();
+
+	/*
+	 * The tuple will become DEAD immediately.  Flag that this page is a
+	 * candidate for pruning by setting xmin to TransactionXmin. While not
+	 * immediately prunable, it is the oldest xid we can cheaply determine
+	 * that's safe against wraparound / being older than the table's
+	 * relfrozenxid.  To defend against the unlikely case of a new relation
+	 * having a newer relfrozenxid than our TransactionXmin, use relfrozenxid
+	 * if so (vacuum can't subsequently move relfrozenxid to beyond
+	 * TransactionXmin, so there's no race here).
+	 */
+	Assert(TransactionIdIsValid(TransactionXmin));
+	if (TransactionIdPrecedes(TransactionXmin, relation->rd_rel->relfrozenxid))
+		prune_xid = relation->rd_rel->relfrozenxid;
+	else
+		prune_xid = TransactionXmin;
+	PageSetPrunable(page, prune_xid);
+
+	/* store transaction information of xact deleting the tuple */
+	tp.t_data->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED);
+	tp.t_data->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+
+	/*
+	 * Set the tuple header xmin to InvalidTransactionId.  This makes the
+	 * tuple immediately invisible everyone.  (In particular, to any
+	 * transactions waiting on the speculative token, woken up later.)
+	 */
+	HeapTupleHeaderSetXmin(tp.t_data, InvalidTransactionId);
+
+	/* Clear the speculative insertion token too */
+	tp.t_data->t_ctid = tp.t_self;
+
+	MarkBufferDirty(buffer);
+
+	/*
+	 * XLOG stuff
+	 *
+	 * The WAL records generated here match heap_delete().  The same recovery
+	 * routines are used.
+	 */
+	if (RelationNeedsWAL(relation))
+	{
+		xl_heap_delete xlrec;
+		XLogRecPtr	recptr;
+
+		xlrec.flags = XLH_DELETE_IS_SUPER;
+		xlrec.infobits_set = compute_infobits(tp.t_data->t_infomask,
+											  tp.t_data->t_infomask2);
+		xlrec.offnum = ItemPointerGetOffsetNumber(&tp.t_self);
+		xlrec.xmax = xid;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, SizeOfHeapDelete);
+		XLogRegisterBuffer(0, buffer, REGBUF_STANDARD);
+
+		/* No replica identity & replication origin logged */
+
+		recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_DELETE);
+
+		PageSetLSN(page, recptr);
+	}
+
+	END_CRIT_SECTION();
+
+	LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+
+	if (HeapTupleHasExternal(&tp))
+	{
+		Assert(!IsToastRelation(relation));
+		heap_toast_delete(relation, &tp, true);
+	}
+
+	/*
+	 * Never need to mark tuple for invalidation, since catalogs don't support
+	 * speculative insertion
+	 */
+
+	/* Now we can release the buffer */
+	ReleaseBuffer(buffer);
+
+	/* count deletion, as we counted the insertion too */
+	pgstat_count_heap_delete(relation);
+}
+
+/*
+ * heap_inplace_update - update a tuple "in place" (ie, overwrite it)
+ *
+ * Overwriting violates both MVCC and transactional safety, so the uses
+ * of this function in Postgres are extremely limited.  Nonetheless we
+ * find some places to use it.
+ *
+ * The tuple cannot change size, and therefore it's reasonable to assume
+ * that its null bitmap (if any) doesn't change either.  So we just
+ * overwrite the data portion of the tuple without touching the null
+ * bitmap or any of the header fields.
+ *
+ * tuple is an in-memory tuple structure containing the data to be written
+ * over the target tuple.  Also, tuple->t_self identifies the target tuple.
+ *
+ * Note that the tuple updated here had better not come directly from the
+ * syscache if the relation has a toast relation as this tuple could
+ * include toast values that have been expanded, causing a failure here.
+ */
+void
+heap_inplace_update(Relation relation, HeapTuple tuple)
+{
+	Buffer		buffer;
+	Page		page;
+	OffsetNumber offnum;
+	ItemId		lp = NULL;
+	HeapTupleHeader htup;
+	uint32		oldlen;
+	uint32		newlen;
+
+	/*
+	 * For now, we don't allow parallel updates.  Unlike a regular update,
+	 * this should never create a combo CID, so it might be possible to relax
+	 * this restriction, but not without more thought and testing.  It's not
+	 * clear that it would be useful, anyway.
+	 */
+	if (IsInParallelMode())
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
+				 errmsg("cannot update tuples during a parallel operation")));
+
+	buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(&(tuple->t_self)));
+	LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+	page = (Page) BufferGetPage(buffer);
+
+	offnum = ItemPointerGetOffsetNumber(&(tuple->t_self));
+	if (PageGetMaxOffsetNumber(page) >= offnum)
+		lp = PageGetItemId(page, offnum);
+
+	if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp))
+		elog(ERROR, "invalid lp");
+
+	htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+	oldlen = ItemIdGetLength(lp) - htup->t_hoff;
+	newlen = tuple->t_len - tuple->t_data->t_hoff;
+	if (oldlen != newlen || htup->t_hoff != tuple->t_data->t_hoff)
+		elog(ERROR, "wrong tuple length");
+
+	/* NO EREPORT(ERROR) from here till changes are logged */
+	START_CRIT_SECTION();
+
+	memcpy((char *) htup + htup->t_hoff,
+		   (char *) tuple->t_data + tuple->t_data->t_hoff,
+		   newlen);
+
+	MarkBufferDirty(buffer);
+
+	/* XLOG stuff */
+	if (RelationNeedsWAL(relation))
+	{
+		xl_heap_inplace xlrec;
+		XLogRecPtr	recptr;
+
+		xlrec.offnum = ItemPointerGetOffsetNumber(&tuple->t_self);
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, SizeOfHeapInplace);
+
+		XLogRegisterBuffer(0, buffer, REGBUF_STANDARD);
+		XLogRegisterBufData(0, (char *) htup + htup->t_hoff, newlen);
+
+		/* inplace updates aren't decoded atm, don't log the origin */
+
+		recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_INPLACE);
+
+		PageSetLSN(page, recptr);
+	}
+
+	END_CRIT_SECTION();
+
+	UnlockReleaseBuffer(buffer);
+
+	/*
+	 * Send out shared cache inval if necessary.  Note that because we only
+	 * pass the new version of the tuple, this mustn't be used for any
+	 * operations that could change catcache lookup keys.  But we aren't
+	 * bothering with index updates either, so that's true a fortiori.
+	 */
+	if (!IsBootstrapProcessingMode())
+		CacheInvalidateHeapTuple(relation, tuple, NULL);
+}
+
+#define		FRM_NOOP				0x0001
+#define		FRM_INVALIDATE_XMAX		0x0002
+#define		FRM_RETURN_IS_XID		0x0004
+#define		FRM_RETURN_IS_MULTI		0x0008
+#define		FRM_MARK_COMMITTED		0x0010
+
+/*
+ * FreezeMultiXactId
+ *		Determine what to do during freezing when a tuple is marked by a
+ *		MultiXactId.
+ *
+ * "flags" is an output value; it's used to tell caller what to do on return.
+ *
+ * "mxid_oldest_xid_out" is an output value; it's used to track the oldest
+ * extant Xid within any Multixact that will remain after freezing executes.
+ *
+ * Possible values that we can set in "flags":
+ * FRM_NOOP
+ *		don't do anything -- keep existing Xmax
+ * FRM_INVALIDATE_XMAX
+ *		mark Xmax as InvalidTransactionId and set XMAX_INVALID flag.
+ * FRM_RETURN_IS_XID
+ *		The Xid return value is a single update Xid to set as xmax.
+ * FRM_MARK_COMMITTED
+ *		Xmax can be marked as HEAP_XMAX_COMMITTED
+ * FRM_RETURN_IS_MULTI
+ *		The return value is a new MultiXactId to set as new Xmax.
+ *		(caller must obtain proper infomask bits using GetMultiXactIdHintBits)
+ *
+ * "mxid_oldest_xid_out" is only set when "flags" contains either FRM_NOOP or
+ * FRM_RETURN_IS_MULTI, since we only leave behind a MultiXactId for these.
+ *
+ * NB: Creates a _new_ MultiXactId when FRM_RETURN_IS_MULTI is set in "flags".
+ */
+static TransactionId
+FreezeMultiXactId(MultiXactId multi, uint16 t_infomask,
+				  TransactionId relfrozenxid, TransactionId relminmxid,
+				  TransactionId cutoff_xid, MultiXactId cutoff_multi,
+				  uint16 *flags, TransactionId *mxid_oldest_xid_out)
+{
+	TransactionId xid = InvalidTransactionId;
+	int			i;
+	MultiXactMember *members;
+	int			nmembers;
+	bool		need_replace;
+	int			nnewmembers;
+	MultiXactMember *newmembers;
+	bool		has_lockers;
+	TransactionId update_xid;
+	bool		update_committed;
+	TransactionId temp_xid_out;
+
+	*flags = 0;
+
+	/* We should only be called in Multis */
+	Assert(t_infomask & HEAP_XMAX_IS_MULTI);
+
+	if (!MultiXactIdIsValid(multi) ||
+		HEAP_LOCKED_UPGRADED(t_infomask))
+	{
+		/* Ensure infomask bits are appropriately set/reset */
+		*flags |= FRM_INVALIDATE_XMAX;
+		return InvalidTransactionId;
+	}
+	else if (MultiXactIdPrecedes(multi, relminmxid))
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg_internal("found multixact %u from before relminmxid %u",
+								 multi, relminmxid)));
+	else if (MultiXactIdPrecedes(multi, cutoff_multi))
+	{
+		/*
+		 * This old multi cannot possibly have members still running, but
+		 * verify just in case.  If it was a locker only, it can be removed
+		 * without any further consideration; but if it contained an update,
+		 * we might need to preserve it.
+		 */
+		if (MultiXactIdIsRunning(multi,
+								 HEAP_XMAX_IS_LOCKED_ONLY(t_infomask)))
+			ereport(ERROR,
+					(errcode(ERRCODE_DATA_CORRUPTED),
+					 errmsg_internal("multixact %u from before cutoff %u found to be still running",
+									 multi, cutoff_multi)));
+
+		if (HEAP_XMAX_IS_LOCKED_ONLY(t_infomask))
+		{
+			*flags |= FRM_INVALIDATE_XMAX;
+			xid = InvalidTransactionId;
+		}
+		else
+		{
+			/* replace multi by update xid */
+			xid = MultiXactIdGetUpdateXid(multi, t_infomask);
+
+			/* wasn't only a lock, xid needs to be valid */
+			Assert(TransactionIdIsValid(xid));
+
+			if (TransactionIdPrecedes(xid, relfrozenxid))
+				ereport(ERROR,
+						(errcode(ERRCODE_DATA_CORRUPTED),
+						 errmsg_internal("found update xid %u from before relfrozenxid %u",
+										 xid, relfrozenxid)));
+
+			/*
+			 * If the xid is older than the cutoff, it has to have aborted,
+			 * otherwise the tuple would have gotten pruned away.
+			 */
+			if (TransactionIdPrecedes(xid, cutoff_xid))
+			{
+				if (TransactionIdDidCommit(xid))
+					ereport(ERROR,
+							(errcode(ERRCODE_DATA_CORRUPTED),
+							 errmsg_internal("cannot freeze committed update xid %u", xid)));
+				*flags |= FRM_INVALIDATE_XMAX;
+				xid = InvalidTransactionId;
+			}
+			else
+			{
+				*flags |= FRM_RETURN_IS_XID;
+			}
+		}
+
+		/*
+		 * Don't push back mxid_oldest_xid_out using FRM_RETURN_IS_XID Xid, or
+		 * when no Xids will remain
+		 */
+		return xid;
+	}
+
+	/*
+	 * This multixact might have or might not have members still running, but
+	 * we know it's valid and is newer than the cutoff point for multis.
+	 * However, some member(s) of it may be below the cutoff for Xids, so we
+	 * need to walk the whole members array to figure out what to do, if
+	 * anything.
+	 */
+
+	nmembers =
+		GetMultiXactIdMembers(multi, &members, false,
+							  HEAP_XMAX_IS_LOCKED_ONLY(t_infomask));
+	if (nmembers <= 0)
+	{
+		/* Nothing worth keeping */
+		*flags |= FRM_INVALIDATE_XMAX;
+		return InvalidTransactionId;
+	}
+
+	/* is there anything older than the cutoff? */
+	need_replace = false;
+	temp_xid_out = *mxid_oldest_xid_out;	/* init for FRM_NOOP */
+	for (i = 0; i < nmembers; i++)
+	{
+		if (TransactionIdPrecedes(members[i].xid, cutoff_xid))
+		{
+			need_replace = true;
+			break;
+		}
+		if (TransactionIdPrecedes(members[i].xid, temp_xid_out))
+			temp_xid_out = members[i].xid;
+	}
+
+	/*
+	 * In the simplest case, there is no member older than the cutoff; we can
+	 * keep the existing MultiXactId as-is, avoiding a more expensive second
+	 * pass over the multi
+	 */
+	if (!need_replace)
+	{
+		/*
+		 * When mxid_oldest_xid_out gets pushed back here it's likely that the
+		 * update Xid was the oldest member, but we don't rely on that
+		 */
+		*flags |= FRM_NOOP;
+		*mxid_oldest_xid_out = temp_xid_out;
+		pfree(members);
+		return multi;
+	}
+
+	/*
+	 * Do a more thorough second pass over the multi to figure out which
+	 * member XIDs actually need to be kept.  Checking the precise status of
+	 * individual members might even show that we don't need to keep anything.
+	 */
+	nnewmembers = 0;
+	newmembers = palloc(sizeof(MultiXactMember) * nmembers);
+	has_lockers = false;
+	update_xid = InvalidTransactionId;
+	update_committed = false;
+	temp_xid_out = *mxid_oldest_xid_out;	/* init for FRM_RETURN_IS_MULTI */
+
+	for (i = 0; i < nmembers; i++)
+	{
+		/*
+		 * Determine whether to keep this member or ignore it.
+		 */
+		if (ISUPDATE_from_mxstatus(members[i].status))
+		{
+			TransactionId xid = members[i].xid;
+
+			Assert(TransactionIdIsValid(xid));
+			if (TransactionIdPrecedes(xid, relfrozenxid))
+				ereport(ERROR,
+						(errcode(ERRCODE_DATA_CORRUPTED),
+						 errmsg_internal("found update xid %u from before relfrozenxid %u",
+										 xid, relfrozenxid)));
+
+			/*
+			 * It's an update; should we keep it?  If the transaction is known
+			 * aborted or crashed then it's okay to ignore it, otherwise not.
+			 * Note that an updater older than cutoff_xid cannot possibly be
+			 * committed, because HeapTupleSatisfiesVacuum would have returned
+			 * HEAPTUPLE_DEAD and we would not be trying to freeze the tuple.
+			 *
+			 * As with all tuple visibility routines, it's critical to test
+			 * TransactionIdIsInProgress before TransactionIdDidCommit,
+			 * because of race conditions explained in detail in
+			 * heapam_visibility.c.
+			 */
+			if (TransactionIdIsCurrentTransactionId(xid) ||
+				TransactionIdIsInProgress(xid))
+			{
+				Assert(!TransactionIdIsValid(update_xid));
+				update_xid = xid;
+			}
+			else if (TransactionIdDidCommit(xid))
+			{
+				/*
+				 * The transaction committed, so we can tell caller to set
+				 * HEAP_XMAX_COMMITTED.  (We can only do this because we know
+				 * the transaction is not running.)
+				 */
+				Assert(!TransactionIdIsValid(update_xid));
+				update_committed = true;
+				update_xid = xid;
+			}
+			else
+			{
+				/*
+				 * Not in progress, not committed -- must be aborted or
+				 * crashed; we can ignore it.
+				 */
+			}
+
+			/*
+			 * Since the tuple wasn't totally removed when vacuum pruned, the
+			 * update Xid cannot possibly be older than the xid cutoff. The
+			 * presence of such a tuple would cause corruption, so be paranoid
+			 * and check.
+			 */
+			if (TransactionIdIsValid(update_xid) &&
+				TransactionIdPrecedes(update_xid, cutoff_xid))
+				ereport(ERROR,
+						(errcode(ERRCODE_DATA_CORRUPTED),
+						 errmsg_internal("found update xid %u from before xid cutoff %u",
+										 update_xid, cutoff_xid)));
+
+			/*
+			 * We determined that this is an Xid corresponding to an update
+			 * that must be retained -- add it to new members list for later.
+			 *
+			 * Also consider pushing back temp_xid_out, which is needed when
+			 * we later conclude that a new multi is required (i.e. when we go
+			 * on to set FRM_RETURN_IS_MULTI for our caller because we also
+			 * need to retain a locker that's still running).
+			 */
+			if (TransactionIdIsValid(update_xid))
+			{
+				newmembers[nnewmembers++] = members[i];
+				if (TransactionIdPrecedes(members[i].xid, temp_xid_out))
+					temp_xid_out = members[i].xid;
+			}
+		}
+		else
+		{
+			/* We only keep lockers if they are still running */
+			if (TransactionIdIsCurrentTransactionId(members[i].xid) ||
+				TransactionIdIsInProgress(members[i].xid))
+			{
+				/*
+				 * Running locker cannot possibly be older than the cutoff.
+				 *
+				 * The cutoff is <= VACUUM's OldestXmin, which is also the
+				 * initial value used for top-level relfrozenxid_out tracking
+				 * state.  A running locker cannot be older than VACUUM's
+				 * OldestXmin, either, so we don't need a temp_xid_out step.
+				 */
+				Assert(TransactionIdIsNormal(members[i].xid));
+				Assert(!TransactionIdPrecedes(members[i].xid, cutoff_xid));
+				Assert(!TransactionIdPrecedes(members[i].xid,
+											  *mxid_oldest_xid_out));
+				newmembers[nnewmembers++] = members[i];
+				has_lockers = true;
+			}
+		}
+	}
+
+	pfree(members);
+
+	/*
+	 * Determine what to do with caller's multi based on information gathered
+	 * during our second pass
+	 */
+	if (nnewmembers == 0)
+	{
+		/* nothing worth keeping!? Tell caller to remove the whole thing */
+		*flags |= FRM_INVALIDATE_XMAX;
+		xid = InvalidTransactionId;
+		/* Don't push back mxid_oldest_xid_out -- no Xids will remain */
+	}
+	else if (TransactionIdIsValid(update_xid) && !has_lockers)
+	{
+		/*
+		 * If there's a single member and it's an update, pass it back alone
+		 * without creating a new Multi.  (XXX we could do this when there's a
+		 * single remaining locker, too, but that would complicate the API too
+		 * much; moreover, the case with the single updater is more
+		 * interesting, because those are longer-lived.)
+		 */
+		Assert(nnewmembers == 1);
+		*flags |= FRM_RETURN_IS_XID;
+		if (update_committed)
+			*flags |= FRM_MARK_COMMITTED;
+		xid = update_xid;
+		/* Don't push back mxid_oldest_xid_out using FRM_RETURN_IS_XID Xid */
+	}
+	else
+	{
+		/*
+		 * Create a new multixact with the surviving members of the previous
+		 * one, to set as new Xmax in the tuple.  The oldest surviving member
+		 * might push back mxid_oldest_xid_out.
+		 */
+		xid = MultiXactIdCreateFromMembers(nnewmembers, newmembers);
+		*flags |= FRM_RETURN_IS_MULTI;
+		*mxid_oldest_xid_out = temp_xid_out;
+	}
+
+	pfree(newmembers);
+
+	return xid;
+}
+
+/*
+ * heap_prepare_freeze_tuple
+ *
+ * Check to see whether any of the XID fields of a tuple (xmin, xmax, xvac)
+ * are older than the specified cutoff XID and cutoff MultiXactId.  If so,
+ * setup enough state (in the *frz output argument) to later execute and
+ * WAL-log what we would need to do, and return true.  Return false if nothing
+ * is to be changed.  In addition, set *totally_frozen to true if the tuple
+ * will be totally frozen after these operations are performed and false if
+ * more freezing will eventually be required.
+ *
+ * Caller must set frz->offset itself, before heap_execute_freeze_tuple call.
+ *
+ * It is assumed that the caller has checked the tuple with
+ * HeapTupleSatisfiesVacuum() and determined that it is not HEAPTUPLE_DEAD
+ * (else we should be removing the tuple, not freezing it).
+ *
+ * The *relfrozenxid_out and *relminmxid_out arguments are the current target
+ * relfrozenxid and relminmxid for VACUUM caller's heap rel.  Any and all
+ * unfrozen XIDs or MXIDs that remain in caller's rel after VACUUM finishes
+ * _must_ have values >= the final relfrozenxid/relminmxid values in pg_class.
+ * This includes XIDs that remain as MultiXact members from any tuple's xmax.
+ * Each call here pushes back *relfrozenxid_out and/or *relminmxid_out as
+ * needed to avoid unsafe final values in rel's authoritative pg_class tuple.
+ *
+ * NB: cutoff_xid *must* be <= VACUUM's OldestXmin, to ensure that any
+ * XID older than it could neither be running nor seen as running by any
+ * open transaction.  This ensures that the replacement will not change
+ * anyone's idea of the tuple state.
+ * Similarly, cutoff_multi must be <= VACUUM's OldestMxact.
+ *
+ * NB: This function has side effects: it might allocate a new MultiXactId.
+ * It will be set as tuple's new xmax when our *frz output is processed within
+ * heap_execute_freeze_tuple later on.  If the tuple is in a shared buffer
+ * then caller had better have an exclusive lock on it already.
+ *
+ * NB: It is not enough to set hint bits to indicate an XID committed/aborted.
+ * The *frz WAL record we output completely removes all old XIDs during REDO.
+ */
+bool
+heap_prepare_freeze_tuple(HeapTupleHeader tuple,
+						  TransactionId relfrozenxid, TransactionId relminmxid,
+						  TransactionId cutoff_xid, TransactionId cutoff_multi,
+						  xl_heap_freeze_tuple *frz, bool *totally_frozen,
+						  TransactionId *relfrozenxid_out,
+						  MultiXactId *relminmxid_out)
+{
+	bool		changed = false;
+	bool		xmax_already_frozen = false;
+	bool		xmin_frozen;
+	bool		freeze_xmax;
+	TransactionId xid;
+
+	frz->frzflags = 0;
+	frz->t_infomask2 = tuple->t_infomask2;
+	frz->t_infomask = tuple->t_infomask;
+	frz->xmax = HeapTupleHeaderGetRawXmax(tuple);
+
+	/*
+	 * Process xmin.  xmin_frozen has two slightly different meanings: in the
+	 * !XidIsNormal case, it means "the xmin doesn't need any freezing" (it's
+	 * already a permanent value), while in the block below it is set true to
+	 * mean "xmin won't need freezing after what we do to it here" (false
+	 * otherwise).  In both cases we're allowed to set totally_frozen, as far
+	 * as xmin is concerned.  Both cases also don't require relfrozenxid_out
+	 * handling, since either way the tuple's xmin will be a permanent value
+	 * once we're done with it.
+	 */
+	xid = HeapTupleHeaderGetXmin(tuple);
+	if (!TransactionIdIsNormal(xid))
+		xmin_frozen = true;
+	else
+	{
+		if (TransactionIdPrecedes(xid, relfrozenxid))
+			ereport(ERROR,
+					(errcode(ERRCODE_DATA_CORRUPTED),
+					 errmsg_internal("found xmin %u from before relfrozenxid %u",
+									 xid, relfrozenxid)));
+
+		xmin_frozen = TransactionIdPrecedes(xid, cutoff_xid);
+		if (xmin_frozen)
+		{
+			if (!TransactionIdDidCommit(xid))
+				ereport(ERROR,
+						(errcode(ERRCODE_DATA_CORRUPTED),
+						 errmsg_internal("uncommitted xmin %u from before xid cutoff %u needs to be frozen",
+										 xid, cutoff_xid)));
+
+			frz->t_infomask |= HEAP_XMIN_FROZEN;
+			changed = true;
+		}
+		else
+		{
+			/* xmin to remain unfrozen.  Could push back relfrozenxid_out. */
+			if (TransactionIdPrecedes(xid, *relfrozenxid_out))
+				*relfrozenxid_out = xid;
+		}
+	}
+
+	/*
+	 * Process xmax.  To thoroughly examine the current Xmax value we need to
+	 * resolve a MultiXactId to its member Xids, in case some of them are
+	 * below the given cutoff for Xids.  In that case, those values might need
+	 * freezing, too.  Also, if a multi needs freezing, we cannot simply take
+	 * it out --- if there's a live updater Xid, it needs to be kept.
+	 *
+	 * Make sure to keep heap_tuple_would_freeze in sync with this.
+	 */
+	xid = HeapTupleHeaderGetRawXmax(tuple);
+
+	if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
+	{
+		TransactionId newxmax;
+		uint16		flags;
+		TransactionId mxid_oldest_xid_out = *relfrozenxid_out;
+
+		newxmax = FreezeMultiXactId(xid, tuple->t_infomask,
+									relfrozenxid, relminmxid,
+									cutoff_xid, cutoff_multi,
+									&flags, &mxid_oldest_xid_out);
+
+		freeze_xmax = (flags & FRM_INVALIDATE_XMAX);
+
+		if (flags & FRM_RETURN_IS_XID)
+		{
+			/*
+			 * xmax will become an updater Xid (original MultiXact's updater
+			 * member Xid will be carried forward as a simple Xid in Xmax).
+			 * Might have to ratchet back relfrozenxid_out here, though never
+			 * relminmxid_out.
+			 */
+			Assert(!freeze_xmax);
+			Assert(TransactionIdIsValid(newxmax));
+			if (TransactionIdPrecedes(newxmax, *relfrozenxid_out))
+				*relfrozenxid_out = newxmax;
+
+			/*
+			 * NB -- some of these transformations are only valid because we
+			 * know the return Xid is a tuple updater (i.e. not merely a
+			 * locker.) Also note that the only reason we don't explicitly
+			 * worry about HEAP_KEYS_UPDATED is because it lives in
+			 * t_infomask2 rather than t_infomask.
+			 */
+			frz->t_infomask &= ~HEAP_XMAX_BITS;
+			frz->xmax = newxmax;
+			if (flags & FRM_MARK_COMMITTED)
+				frz->t_infomask |= HEAP_XMAX_COMMITTED;
+			changed = true;
+		}
+		else if (flags & FRM_RETURN_IS_MULTI)
+		{
+			uint16		newbits;
+			uint16		newbits2;
+
+			/*
+			 * xmax is an old MultiXactId that we have to replace with a new
+			 * MultiXactId, to carry forward two or more original member XIDs.
+			 * Might have to ratchet back relfrozenxid_out here, though never
+			 * relminmxid_out.
+			 */
+			Assert(!freeze_xmax);
+			Assert(MultiXactIdIsValid(newxmax));
+			Assert(!MultiXactIdPrecedes(newxmax, *relminmxid_out));
+			Assert(TransactionIdPrecedesOrEquals(mxid_oldest_xid_out,
+												 *relfrozenxid_out));
+			*relfrozenxid_out = mxid_oldest_xid_out;
+
+			/*
+			 * We can't use GetMultiXactIdHintBits directly on the new multi
+			 * here; that routine initializes the masks to all zeroes, which
+			 * would lose other bits we need.  Doing it this way ensures all
+			 * unrelated bits remain untouched.
+			 */
+			frz->t_infomask &= ~HEAP_XMAX_BITS;
+			frz->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+			GetMultiXactIdHintBits(newxmax, &newbits, &newbits2);
+			frz->t_infomask |= newbits;
+			frz->t_infomask2 |= newbits2;
+
+			frz->xmax = newxmax;
+
+			changed = true;
+		}
+		else if (flags & FRM_NOOP)
+		{
+			/*
+			 * xmax is a MultiXactId, and nothing about it changes for now.
+			 * Might have to ratchet back relminmxid_out, relfrozenxid_out, or
+			 * both together.
+			 */
+			Assert(!freeze_xmax);
+			Assert(MultiXactIdIsValid(newxmax) && xid == newxmax);
+			Assert(TransactionIdPrecedesOrEquals(mxid_oldest_xid_out,
+												 *relfrozenxid_out));
+			if (MultiXactIdPrecedes(xid, *relminmxid_out))
+				*relminmxid_out = xid;
+			*relfrozenxid_out = mxid_oldest_xid_out;
+		}
+		else
+		{
+			/*
+			 * Keeping nothing (neither an Xid nor a MultiXactId) in xmax.
+			 * Won't have to ratchet back relminmxid_out or relfrozenxid_out.
+			 */
+			Assert(freeze_xmax);
+			Assert(!TransactionIdIsValid(newxmax));
+		}
+	}
+	else if (TransactionIdIsNormal(xid))
+	{
+		if (TransactionIdPrecedes(xid, relfrozenxid))
+			ereport(ERROR,
+					(errcode(ERRCODE_DATA_CORRUPTED),
+					 errmsg_internal("found xmax %u from before relfrozenxid %u",
+									 xid, relfrozenxid)));
+
+		if (TransactionIdPrecedes(xid, cutoff_xid))
+		{
+			/*
+			 * If we freeze xmax, make absolutely sure that it's not an XID
+			 * that is important.  (Note, a lock-only xmax can be removed
+			 * independent of committedness, since a committed lock holder has
+			 * released the lock).
+			 */
+			if (!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask) &&
+				TransactionIdDidCommit(xid))
+				ereport(ERROR,
+						(errcode(ERRCODE_DATA_CORRUPTED),
+						 errmsg_internal("cannot freeze committed xmax %u",
+										 xid)));
+			freeze_xmax = true;
+			/* No need for relfrozenxid_out handling, since we'll freeze xmax */
+		}
+		else
+		{
+			freeze_xmax = false;
+			if (TransactionIdPrecedes(xid, *relfrozenxid_out))
+				*relfrozenxid_out = xid;
+		}
+	}
+	else if ((tuple->t_infomask & HEAP_XMAX_INVALID) ||
+			 !TransactionIdIsValid(HeapTupleHeaderGetRawXmax(tuple)))
+	{
+		freeze_xmax = false;
+		xmax_already_frozen = true;
+		/* No need for relfrozenxid_out handling for already-frozen xmax */
+	}
+	else
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg_internal("found xmax %u (infomask 0x%04x) not frozen, not multi, not normal",
+								 xid, tuple->t_infomask)));
+
+	if (freeze_xmax)
+	{
+		Assert(!xmax_already_frozen);
+
+		frz->xmax = InvalidTransactionId;
+
+		/*
+		 * The tuple might be marked either XMAX_INVALID or XMAX_COMMITTED +
+		 * LOCKED.  Normalize to INVALID just to be sure no one gets confused.
+		 * Also get rid of the HEAP_KEYS_UPDATED bit.
+		 */
+		frz->t_infomask &= ~HEAP_XMAX_BITS;
+		frz->t_infomask |= HEAP_XMAX_INVALID;
+		frz->t_infomask2 &= ~HEAP_HOT_UPDATED;
+		frz->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+		changed = true;
+	}
+
+	/*
+	 * Old-style VACUUM FULL is gone, but we have to keep this code as long as
+	 * we support having MOVED_OFF/MOVED_IN tuples in the database.
+	 */
+	if (tuple->t_infomask & HEAP_MOVED)
+	{
+		xid = HeapTupleHeaderGetXvac(tuple);
+
+		/*
+		 * For Xvac, we ignore the cutoff_xid and just always perform the
+		 * freeze operation.  The oldest release in which such a value can
+		 * actually be set is PostgreSQL 8.4, because old-style VACUUM FULL
+		 * was removed in PostgreSQL 9.0.  Note that if we were to respect
+		 * cutoff_xid here, we'd need to make surely to clear totally_frozen
+		 * when we skipped freezing on that basis.
+		 *
+		 * No need for relfrozenxid_out handling, since we always freeze xvac.
+		 */
+		if (TransactionIdIsNormal(xid))
+		{
+			/*
+			 * If a MOVED_OFF tuple is not dead, the xvac transaction must
+			 * have failed; whereas a non-dead MOVED_IN tuple must mean the
+			 * xvac transaction succeeded.
+			 */
+			if (tuple->t_infomask & HEAP_MOVED_OFF)
+				frz->frzflags |= XLH_INVALID_XVAC;
+			else
+				frz->frzflags |= XLH_FREEZE_XVAC;
+
+			/*
+			 * Might as well fix the hint bits too; usually XMIN_COMMITTED
+			 * will already be set here, but there's a small chance not.
+			 */
+			Assert(!(tuple->t_infomask & HEAP_XMIN_INVALID));
+			frz->t_infomask |= HEAP_XMIN_COMMITTED;
+			changed = true;
+		}
+	}
+
+	*totally_frozen = (xmin_frozen &&
+					   (freeze_xmax || xmax_already_frozen));
+	return changed;
+}
+
+/*
+ * heap_execute_freeze_tuple
+ *		Execute the prepared freezing of a tuple.
+ *
+ * Caller is responsible for ensuring that no other backend can access the
+ * storage underlying this tuple, either by holding an exclusive lock on the
+ * buffer containing it (which is what lazy VACUUM does), or by having it be
+ * in private storage (which is what CLUSTER and friends do).
+ *
+ * Note: it might seem we could make the changes without exclusive lock, since
+ * TransactionId read/write is assumed atomic anyway.  However there is a race
+ * condition: someone who just fetched an old XID that we overwrite here could
+ * conceivably not finish checking the XID against pg_xact before we finish
+ * the VACUUM and perhaps truncate off the part of pg_xact he needs.  Getting
+ * exclusive lock ensures no other backend is in process of checking the
+ * tuple status.  Also, getting exclusive lock makes it safe to adjust the
+ * infomask bits.
+ *
+ * NB: All code in here must be safe to execute during crash recovery!
+ */
+void
+heap_execute_freeze_tuple(HeapTupleHeader tuple, xl_heap_freeze_tuple *frz)
+{
+	HeapTupleHeaderSetXmax(tuple, frz->xmax);
+
+	if (frz->frzflags & XLH_FREEZE_XVAC)
+		HeapTupleHeaderSetXvac(tuple, FrozenTransactionId);
+
+	if (frz->frzflags & XLH_INVALID_XVAC)
+		HeapTupleHeaderSetXvac(tuple, InvalidTransactionId);
+
+	tuple->t_infomask = frz->t_infomask;
+	tuple->t_infomask2 = frz->t_infomask2;
+}
+
+/*
+ * heap_freeze_tuple
+ *		Freeze tuple in place, without WAL logging.
+ *
+ * Useful for callers like CLUSTER that perform their own WAL logging.
+ */
+bool
+heap_freeze_tuple(HeapTupleHeader tuple,
+				  TransactionId relfrozenxid, TransactionId relminmxid,
+				  TransactionId cutoff_xid, TransactionId cutoff_multi)
+{
+	xl_heap_freeze_tuple frz;
+	bool		do_freeze;
+	bool		tuple_totally_frozen;
+	TransactionId relfrozenxid_out = cutoff_xid;
+	MultiXactId relminmxid_out = cutoff_multi;
+
+	do_freeze = heap_prepare_freeze_tuple(tuple,
+										  relfrozenxid, relminmxid,
+										  cutoff_xid, cutoff_multi,
+										  &frz, &tuple_totally_frozen,
+										  &relfrozenxid_out, &relminmxid_out);
+
+	/*
+	 * Note that because this is not a WAL-logged operation, we don't need to
+	 * fill in the offset in the freeze record.
+	 */
+
+	if (do_freeze)
+		heap_execute_freeze_tuple(tuple, &frz);
+	return do_freeze;
+}
+
+/*
+ * For a given MultiXactId, return the hint bits that should be set in the
+ * tuple's infomask.
+ *
+ * Normally this should be called for a multixact that was just created, and
+ * so is on our local cache, so the GetMembers call is fast.
+ */
+static void
+GetMultiXactIdHintBits(MultiXactId multi, uint16 *new_infomask,
+					   uint16 *new_infomask2)
+{
+	int			nmembers;
+	MultiXactMember *members;
+	int			i;
+	uint16		bits = HEAP_XMAX_IS_MULTI;
+	uint16		bits2 = 0;
+	bool		has_update = false;
+	LockTupleMode strongest = LockTupleKeyShare;
+
+	/*
+	 * We only use this in multis we just created, so they cannot be values
+	 * pre-pg_upgrade.
+	 */
+	nmembers = GetMultiXactIdMembers(multi, &members, false, false);
+
+	for (i = 0; i < nmembers; i++)
+	{
+		LockTupleMode mode;
+
+		/*
+		 * Remember the strongest lock mode held by any member of the
+		 * multixact.
+		 */
+		mode = TUPLOCK_from_mxstatus(members[i].status);
+		if (mode > strongest)
+			strongest = mode;
+
+		/* See what other bits we need */
+		switch (members[i].status)
+		{
+			case MultiXactStatusForKeyShare:
+			case MultiXactStatusForShare:
+			case MultiXactStatusForNoKeyUpdate:
+				break;
+
+			case MultiXactStatusForUpdate:
+				bits2 |= HEAP_KEYS_UPDATED;
+				break;
+
+			case MultiXactStatusNoKeyUpdate:
+				has_update = true;
+				break;
+
+			case MultiXactStatusUpdate:
+				bits2 |= HEAP_KEYS_UPDATED;
+				has_update = true;
+				break;
+		}
+	}
+
+	if (strongest == LockTupleExclusive ||
+		strongest == LockTupleNoKeyExclusive)
+		bits |= HEAP_XMAX_EXCL_LOCK;
+	else if (strongest == LockTupleShare)
+		bits |= HEAP_XMAX_SHR_LOCK;
+	else if (strongest == LockTupleKeyShare)
+		bits |= HEAP_XMAX_KEYSHR_LOCK;
+
+	if (!has_update)
+		bits |= HEAP_XMAX_LOCK_ONLY;
+
+	if (nmembers > 0)
+		pfree(members);
+
+	*new_infomask = bits;
+	*new_infomask2 = bits2;
+}
+
+/*
+ * MultiXactIdGetUpdateXid
+ *
+ * Given a multixact Xmax and corresponding infomask, which does not have the
+ * HEAP_XMAX_LOCK_ONLY bit set, obtain and return the Xid of the updating
+ * transaction.
+ *
+ * Caller is expected to check the status of the updating transaction, if
+ * necessary.
+ */
+static TransactionId
+MultiXactIdGetUpdateXid(TransactionId xmax, uint16 t_infomask)
+{
+	TransactionId update_xact = InvalidTransactionId;
+	MultiXactMember *members;
+	int			nmembers;
+
+	Assert(!(t_infomask & HEAP_XMAX_LOCK_ONLY));
+	Assert(t_infomask & HEAP_XMAX_IS_MULTI);
+
+	/*
+	 * Since we know the LOCK_ONLY bit is not set, this cannot be a multi from
+	 * pre-pg_upgrade.
+	 */
+	nmembers = GetMultiXactIdMembers(xmax, &members, false, false);
+
+	if (nmembers > 0)
+	{
+		int			i;
+
+		for (i = 0; i < nmembers; i++)
+		{
+			/* Ignore lockers */
+			if (!ISUPDATE_from_mxstatus(members[i].status))
+				continue;
+
+			/* there can be at most one updater */
+			Assert(update_xact == InvalidTransactionId);
+			update_xact = members[i].xid;
+#ifndef USE_ASSERT_CHECKING
+
+			/*
+			 * in an assert-enabled build, walk the whole array to ensure
+			 * there's no other updater.
+			 */
+			break;
+#endif
+		}
+
+		pfree(members);
+	}
+
+	return update_xact;
+}
+
+/*
+ * HeapTupleGetUpdateXid
+ *		As above, but use a HeapTupleHeader
+ *
+ * See also HeapTupleHeaderGetUpdateXid, which can be used without previously
+ * checking the hint bits.
+ */
+TransactionId
+HeapTupleGetUpdateXid(HeapTupleHeader tuple)
+{
+	return MultiXactIdGetUpdateXid(HeapTupleHeaderGetRawXmax(tuple),
+								   tuple->t_infomask);
+}
+
+/*
+ * Does the given multixact conflict with the current transaction grabbing a
+ * tuple lock of the given strength?
+ *
+ * The passed infomask pairs up with the given multixact in the tuple header.
+ *
+ * If current_is_member is not NULL, it is set to 'true' if the current
+ * transaction is a member of the given multixact.
+ */
+static bool
+DoesMultiXactIdConflict(MultiXactId multi, uint16 infomask,
+						LockTupleMode lockmode, bool *current_is_member)
+{
+	int			nmembers;
+	MultiXactMember *members;
+	bool		result = false;
+	LOCKMODE	wanted = tupleLockExtraInfo[lockmode].hwlock;
+
+	if (HEAP_LOCKED_UPGRADED(infomask))
+		return false;
+
+	nmembers = GetMultiXactIdMembers(multi, &members, false,
+									 HEAP_XMAX_IS_LOCKED_ONLY(infomask));
+	if (nmembers >= 0)
+	{
+		int			i;
+
+		for (i = 0; i < nmembers; i++)
+		{
+			TransactionId memxid;
+			LOCKMODE	memlockmode;
+
+			if (result && (current_is_member == NULL || *current_is_member))
+				break;
+
+			memlockmode = LOCKMODE_from_mxstatus(members[i].status);
+
+			/* ignore members from current xact (but track their presence) */
+			memxid = members[i].xid;
+			if (TransactionIdIsCurrentTransactionId(memxid))
+			{
+				if (current_is_member != NULL)
+					*current_is_member = true;
+				continue;
+			}
+			else if (result)
+				continue;
+
+			/* ignore members that don't conflict with the lock we want */
+			if (!DoLockModesConflict(memlockmode, wanted))
+				continue;
+
+			if (ISUPDATE_from_mxstatus(members[i].status))
+			{
+				/* ignore aborted updaters */
+				if (TransactionIdDidAbort(memxid))
+					continue;
+			}
+			else
+			{
+				/* ignore lockers-only that are no longer in progress */
+				if (!TransactionIdIsInProgress(memxid))
+					continue;
+			}
+
+			/*
+			 * Whatever remains are either live lockers that conflict with our
+			 * wanted lock, and updaters that are not aborted.  Those conflict
+			 * with what we want.  Set up to return true, but keep going to
+			 * look for the current transaction among the multixact members,
+			 * if needed.
+			 */
+			result = true;
+		}
+		pfree(members);
+	}
+
+	return result;
+}
+
+/*
+ * Do_MultiXactIdWait
+ *		Actual implementation for the two functions below.
+ *
+ * 'multi', 'status' and 'infomask' indicate what to sleep on (the status is
+ * needed to ensure we only sleep on conflicting members, and the infomask is
+ * used to optimize multixact access in case it's a lock-only multi); 'nowait'
+ * indicates whether to use conditional lock acquisition, to allow callers to
+ * fail if lock is unavailable.  'rel', 'ctid' and 'oper' are used to set up
+ * context information for error messages.  'remaining', if not NULL, receives
+ * the number of members that are still running, including any (non-aborted)
+ * subtransactions of our own transaction.
+ *
+ * We do this by sleeping on each member using XactLockTableWait.  Any
+ * members that belong to the current backend are *not* waited for, however;
+ * this would not merely be useless but would lead to Assert failure inside
+ * XactLockTableWait.  By the time this returns, it is certain that all
+ * transactions *of other backends* that were members of the MultiXactId
+ * that conflict with the requested status are dead (and no new ones can have
+ * been added, since it is not legal to add members to an existing
+ * MultiXactId).
+ *
+ * But by the time we finish sleeping, someone else may have changed the Xmax
+ * of the containing tuple, so the caller needs to iterate on us somehow.
+ *
+ * Note that in case we return false, the number of remaining members is
+ * not to be trusted.
+ */
+static bool
+Do_MultiXactIdWait(MultiXactId multi, MultiXactStatus status,
+				   uint16 infomask, bool nowait,
+				   Relation rel, ItemPointer ctid, XLTW_Oper oper,
+				   int *remaining)
+{
+	bool		result = true;
+	MultiXactMember *members;
+	int			nmembers;
+	int			remain = 0;
+
+	/* for pre-pg_upgrade tuples, no need to sleep at all */
+	nmembers = HEAP_LOCKED_UPGRADED(infomask) ? -1 :
+		GetMultiXactIdMembers(multi, &members, false,
+							  HEAP_XMAX_IS_LOCKED_ONLY(infomask));
+
+	if (nmembers >= 0)
+	{
+		int			i;
+
+		for (i = 0; i < nmembers; i++)
+		{
+			TransactionId memxid = members[i].xid;
+			MultiXactStatus memstatus = members[i].status;
+
+			if (TransactionIdIsCurrentTransactionId(memxid))
+			{
+				remain++;
+				continue;
+			}
+
+			if (!DoLockModesConflict(LOCKMODE_from_mxstatus(memstatus),
+									 LOCKMODE_from_mxstatus(status)))
+			{
+				if (remaining && TransactionIdIsInProgress(memxid))
+					remain++;
+				continue;
+			}
+
+			/*
+			 * This member conflicts with our multi, so we have to sleep (or
+			 * return failure, if asked to avoid waiting.)
+			 *
+			 * Note that we don't set up an error context callback ourselves,
+			 * but instead we pass the info down to XactLockTableWait.  This
+			 * might seem a bit wasteful because the context is set up and
+			 * tore down for each member of the multixact, but in reality it
+			 * should be barely noticeable, and it avoids duplicate code.
+			 */
+			if (nowait)
+			{
+				result = ConditionalXactLockTableWait(memxid);
+				if (!result)
+					break;
+			}
+			else
+				XactLockTableWait(memxid, rel, ctid, oper);
+		}
+
+		pfree(members);
+	}
+
+	if (remaining)
+		*remaining = remain;
+
+	return result;
+}
+
+/*
+ * MultiXactIdWait
+ *		Sleep on a MultiXactId.
+ *
+ * By the time we finish sleeping, someone else may have changed the Xmax
+ * of the containing tuple, so the caller needs to iterate on us somehow.
+ *
+ * We return (in *remaining, if not NULL) the number of members that are still
+ * running, including any (non-aborted) subtransactions of our own transaction.
+ */
+static void
+MultiXactIdWait(MultiXactId multi, MultiXactStatus status, uint16 infomask,
+				Relation rel, ItemPointer ctid, XLTW_Oper oper,
+				int *remaining)
+{
+	(void) Do_MultiXactIdWait(multi, status, infomask, false,
+							  rel, ctid, oper, remaining);
+}
+
+/*
+ * ConditionalMultiXactIdWait
+ *		As above, but only lock if we can get the lock without blocking.
+ *
+ * By the time we finish sleeping, someone else may have changed the Xmax
+ * of the containing tuple, so the caller needs to iterate on us somehow.
+ *
+ * If the multixact is now all gone, return true.  Returns false if some
+ * transactions might still be running.
+ *
+ * We return (in *remaining, if not NULL) the number of members that are still
+ * running, including any (non-aborted) subtransactions of our own transaction.
+ */
+static bool
+ConditionalMultiXactIdWait(MultiXactId multi, MultiXactStatus status,
+						   uint16 infomask, Relation rel, int *remaining)
+{
+	return Do_MultiXactIdWait(multi, status, infomask, true,
+							  rel, NULL, XLTW_None, remaining);
+}
+
+/*
+ * heap_tuple_needs_eventual_freeze
+ *
+ * Check to see whether any of the XID fields of a tuple (xmin, xmax, xvac)
+ * will eventually require freezing (if tuple isn't removed by pruning first).
+ */
+bool
+heap_tuple_needs_eventual_freeze(HeapTupleHeader tuple)
+{
+	TransactionId xid;
+
+	/*
+	 * If xmin is a normal transaction ID, this tuple is definitely not
+	 * frozen.
+	 */
+	xid = HeapTupleHeaderGetXmin(tuple);
+	if (TransactionIdIsNormal(xid))
+		return true;
+
+	/*
+	 * If xmax is a valid xact or multixact, this tuple is also not frozen.
+	 */
+	if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
+	{
+		MultiXactId multi;
+
+		multi = HeapTupleHeaderGetRawXmax(tuple);
+		if (MultiXactIdIsValid(multi))
+			return true;
+	}
+	else
+	{
+		xid = HeapTupleHeaderGetRawXmax(tuple);
+		if (TransactionIdIsNormal(xid))
+			return true;
+	}
+
+	if (tuple->t_infomask & HEAP_MOVED)
+	{
+		xid = HeapTupleHeaderGetXvac(tuple);
+		if (TransactionIdIsNormal(xid))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * heap_tuple_would_freeze
+ *
+ * Return value indicates if heap_prepare_freeze_tuple sibling function would
+ * freeze any of the XID/XMID fields from the tuple, given the same cutoffs.
+ * We must also deal with dead tuples here, since (xmin, xmax, xvac) fields
+ * could be processed by pruning away the whole tuple instead of freezing.
+ *
+ * The *relfrozenxid_out and *relminmxid_out input/output arguments work just
+ * like the heap_prepare_freeze_tuple arguments that they're based on.  We
+ * never freeze here, which makes tracking the oldest extant XID/MXID simple.
+ */
+bool
+heap_tuple_would_freeze(HeapTupleHeader tuple, TransactionId cutoff_xid,
+						MultiXactId cutoff_multi,
+						TransactionId *relfrozenxid_out,
+						MultiXactId *relminmxid_out)
+{
+	TransactionId xid;
+	MultiXactId multi;
+	bool		would_freeze = false;
+
+	/* First deal with xmin */
+	xid = HeapTupleHeaderGetXmin(tuple);
+	if (TransactionIdIsNormal(xid))
+	{
+		if (TransactionIdPrecedes(xid, *relfrozenxid_out))
+			*relfrozenxid_out = xid;
+		if (TransactionIdPrecedes(xid, cutoff_xid))
+			would_freeze = true;
+	}
+
+	/* Now deal with xmax */
+	xid = InvalidTransactionId;
+	multi = InvalidMultiXactId;
+	if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
+		multi = HeapTupleHeaderGetRawXmax(tuple);
+	else
+		xid = HeapTupleHeaderGetRawXmax(tuple);
+
+	if (TransactionIdIsNormal(xid))
+	{
+		/* xmax is a non-permanent XID */
+		if (TransactionIdPrecedes(xid, *relfrozenxid_out))
+			*relfrozenxid_out = xid;
+		if (TransactionIdPrecedes(xid, cutoff_xid))
+			would_freeze = true;
+	}
+	else if (!MultiXactIdIsValid(multi))
+	{
+		/* xmax is a permanent XID or invalid MultiXactId/XID */
+	}
+	else if (HEAP_LOCKED_UPGRADED(tuple->t_infomask))
+	{
+		/* xmax is a pg_upgrade'd MultiXact, which can't have updater XID */
+		if (MultiXactIdPrecedes(multi, *relminmxid_out))
+			*relminmxid_out = multi;
+		/* heap_prepare_freeze_tuple always freezes pg_upgrade'd xmax */
+		would_freeze = true;
+	}
+	else
+	{
+		/* xmax is a MultiXactId that may have an updater XID */
+		MultiXactMember *members;
+		int			nmembers;
+
+		if (MultiXactIdPrecedes(multi, *relminmxid_out))
+			*relminmxid_out = multi;
+		if (MultiXactIdPrecedes(multi, cutoff_multi))
+			would_freeze = true;
+
+		/* need to check whether any member of the mxact is old */
+		nmembers = GetMultiXactIdMembers(multi, &members, false,
+										 HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask));
+
+		for (int i = 0; i < nmembers; i++)
+		{
+			xid = members[i].xid;
+			Assert(TransactionIdIsNormal(xid));
+			if (TransactionIdPrecedes(xid, *relfrozenxid_out))
+				*relfrozenxid_out = xid;
+			if (TransactionIdPrecedes(xid, cutoff_xid))
+				would_freeze = true;
+		}
+		if (nmembers > 0)
+			pfree(members);
+	}
+
+	if (tuple->t_infomask & HEAP_MOVED)
+	{
+		xid = HeapTupleHeaderGetXvac(tuple);
+		if (TransactionIdIsNormal(xid))
+		{
+			if (TransactionIdPrecedes(xid, *relfrozenxid_out))
+				*relfrozenxid_out = xid;
+			/* heap_prepare_freeze_tuple always freezes xvac */
+			would_freeze = true;
+		}
+	}
+
+	return would_freeze;
+}
+
+/*
+ * If 'tuple' contains any visible XID greater than latestRemovedXid,
+ * ratchet forwards latestRemovedXid to the greatest one found.
+ * This is used as the basis for generating Hot Standby conflicts, so
+ * if a tuple was never visible then removing it should not conflict
+ * with queries.
+ */
+void
+HeapTupleHeaderAdvanceLatestRemovedXid(HeapTupleHeader tuple,
+									   TransactionId *latestRemovedXid)
+{
+	TransactionId xmin = HeapTupleHeaderGetXmin(tuple);
+	TransactionId xmax = HeapTupleHeaderGetUpdateXid(tuple);
+	TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
+
+	if (tuple->t_infomask & HEAP_MOVED)
+	{
+		if (TransactionIdPrecedes(*latestRemovedXid, xvac))
+			*latestRemovedXid = xvac;
+	}
+
+	/*
+	 * Ignore tuples inserted by an aborted transaction or if the tuple was
+	 * updated/deleted by the inserting transaction.
+	 *
+	 * Look for a committed hint bit, or if no xmin bit is set, check clog.
+	 */
+	if (HeapTupleHeaderXminCommitted(tuple) ||
+		(!HeapTupleHeaderXminInvalid(tuple) && TransactionIdDidCommit(xmin)))
+	{
+		if (xmax != xmin &&
+			TransactionIdFollows(xmax, *latestRemovedXid))
+			*latestRemovedXid = xmax;
+	}
+
+	/* *latestRemovedXid may still be invalid at end */
+}
+
+#ifdef USE_PREFETCH
+/*
+ * Helper function for heap_index_delete_tuples.  Issues prefetch requests for
+ * prefetch_count buffers.  The prefetch_state keeps track of all the buffers
+ * we can prefetch, and which have already been prefetched; each call to this
+ * function picks up where the previous call left off.
+ *
+ * Note: we expect the deltids array to be sorted in an order that groups TIDs
+ * by heap block, with all TIDs for each block appearing together in exactly
+ * one group.
+ */
+static void
+index_delete_prefetch_buffer(Relation rel,
+							 IndexDeletePrefetchState *prefetch_state,
+							 int prefetch_count)
+{
+	BlockNumber cur_hblkno = prefetch_state->cur_hblkno;
+	int			count = 0;
+	int			i;
+	int			ndeltids = prefetch_state->ndeltids;
+	TM_IndexDelete *deltids = prefetch_state->deltids;
+
+	for (i = prefetch_state->next_item;
+		 i < ndeltids && count < prefetch_count;
+		 i++)
+	{
+		ItemPointer htid = &deltids[i].tid;
+
+		if (cur_hblkno == InvalidBlockNumber ||
+			ItemPointerGetBlockNumber(htid) != cur_hblkno)
+		{
+			cur_hblkno = ItemPointerGetBlockNumber(htid);
+			PrefetchBuffer(rel, MAIN_FORKNUM, cur_hblkno);
+			count++;
+		}
+	}
+
+	/*
+	 * Save the prefetch position so that next time we can continue from that
+	 * position.
+	 */
+	prefetch_state->next_item = i;
+	prefetch_state->cur_hblkno = cur_hblkno;
+}
+#endif
+
+/*
+ * Helper function for heap_index_delete_tuples.  Checks for index corruption
+ * involving an invalid TID in index AM caller's index page.
+ *
+ * This is an ideal place for these checks.  The index AM must hold a buffer
+ * lock on the index page containing the TIDs we examine here, so we don't
+ * have to worry about concurrent VACUUMs at all.  We can be sure that the
+ * index is corrupt when htid points directly to an LP_UNUSED item or
+ * heap-only tuple, which is not the case during standard index scans.
+ */
+static inline void
+index_delete_check_htid(TM_IndexDeleteOp *delstate,
+						Page page, OffsetNumber maxoff,
+						ItemPointer htid, TM_IndexStatus *istatus)
+{
+	OffsetNumber indexpagehoffnum = ItemPointerGetOffsetNumber(htid);
+	ItemId		iid;
+
+	Assert(OffsetNumberIsValid(istatus->idxoffnum));
+
+	if (unlikely(indexpagehoffnum > maxoff))
+		ereport(ERROR,
+				(errcode(ERRCODE_INDEX_CORRUPTED),
+				 errmsg_internal("heap tid from index tuple (%u,%u) points past end of heap page line pointer array at offset %u of block %u in index \"%s\"",
+								 ItemPointerGetBlockNumber(htid),
+								 indexpagehoffnum,
+								 istatus->idxoffnum, delstate->iblknum,
+								 RelationGetRelationName(delstate->irel))));
+
+	iid = PageGetItemId(page, indexpagehoffnum);
+	if (unlikely(!ItemIdIsUsed(iid)))
+		ereport(ERROR,
+				(errcode(ERRCODE_INDEX_CORRUPTED),
+				 errmsg_internal("heap tid from index tuple (%u,%u) points to unused heap page item at offset %u of block %u in index \"%s\"",
+								 ItemPointerGetBlockNumber(htid),
+								 indexpagehoffnum,
+								 istatus->idxoffnum, delstate->iblknum,
+								 RelationGetRelationName(delstate->irel))));
+
+	if (ItemIdHasStorage(iid))
+	{
+		HeapTupleHeader htup;
+
+		Assert(ItemIdIsNormal(iid));
+		htup = (HeapTupleHeader) PageGetItem(page, iid);
+
+		if (unlikely(HeapTupleHeaderIsHeapOnly(htup)))
+			ereport(ERROR,
+					(errcode(ERRCODE_INDEX_CORRUPTED),
+					 errmsg_internal("heap tid from index tuple (%u,%u) points to heap-only tuple at offset %u of block %u in index \"%s\"",
+									 ItemPointerGetBlockNumber(htid),
+									 indexpagehoffnum,
+									 istatus->idxoffnum, delstate->iblknum,
+									 RelationGetRelationName(delstate->irel))));
+	}
+}
+
+/*
+ * heapam implementation of tableam's index_delete_tuples interface.
+ *
+ * This helper function is called by index AMs during index tuple deletion.
+ * See tableam header comments for an explanation of the interface implemented
+ * here and a general theory of operation.  Note that each call here is either
+ * a simple index deletion call, or a bottom-up index deletion call.
+ *
+ * It's possible for this to generate a fair amount of I/O, since we may be
+ * deleting hundreds of tuples from a single index block.  To amortize that
+ * cost to some degree, this uses prefetching and combines repeat accesses to
+ * the same heap block.
+ */
+TransactionId
+heap_index_delete_tuples(Relation rel, TM_IndexDeleteOp *delstate)
+{
+	/* Initial assumption is that earlier pruning took care of conflict */
+	TransactionId latestRemovedXid = InvalidTransactionId;
+	BlockNumber blkno = InvalidBlockNumber;
+	Buffer		buf = InvalidBuffer;
+	Page		page = NULL;
+	OffsetNumber maxoff = InvalidOffsetNumber;
+	TransactionId priorXmax;
+#ifdef USE_PREFETCH
+	IndexDeletePrefetchState prefetch_state;
+	int			prefetch_distance;
+#endif
+	SnapshotData SnapshotNonVacuumable;
+	int			finalndeltids = 0,
+				nblocksaccessed = 0;
+
+	/* State that's only used in bottom-up index deletion case */
+	int			nblocksfavorable = 0;
+	int			curtargetfreespace = delstate->bottomupfreespace,
+				lastfreespace = 0,
+				actualfreespace = 0;
+	bool		bottomup_final_block = false;
+
+	InitNonVacuumableSnapshot(SnapshotNonVacuumable, GlobalVisTestFor(rel));
+
+	/* Sort caller's deltids array by TID for further processing */
+	index_delete_sort(delstate);
+
+	/*
+	 * Bottom-up case: resort deltids array in an order attuned to where the
+	 * greatest number of promising TIDs are to be found, and determine how
+	 * many blocks from the start of sorted array should be considered
+	 * favorable.  This will also shrink the deltids array in order to
+	 * eliminate completely unfavorable blocks up front.
+	 */
+	if (delstate->bottomup)
+		nblocksfavorable = bottomup_sort_and_shrink(delstate);
+
+#ifdef USE_PREFETCH
+	/* Initialize prefetch state. */
+	prefetch_state.cur_hblkno = InvalidBlockNumber;
+	prefetch_state.next_item = 0;
+	prefetch_state.ndeltids = delstate->ndeltids;
+	prefetch_state.deltids = delstate->deltids;
+
+	/*
+	 * Determine the prefetch distance that we will attempt to maintain.
+	 *
+	 * Since the caller holds a buffer lock somewhere in rel, we'd better make
+	 * sure that isn't a catalog relation before we call code that does
+	 * syscache lookups, to avoid risk of deadlock.
+	 */
+	if (IsCatalogRelation(rel))
+		prefetch_distance = maintenance_io_concurrency;
+	else
+		prefetch_distance =
+			get_tablespace_maintenance_io_concurrency(rel->rd_rel->reltablespace);
+
+	/* Cap initial prefetch distance for bottom-up deletion caller */
+	if (delstate->bottomup)
+	{
+		Assert(nblocksfavorable >= 1);
+		Assert(nblocksfavorable <= BOTTOMUP_MAX_NBLOCKS);
+		prefetch_distance = Min(prefetch_distance, nblocksfavorable);
+	}
+
+	/* Start prefetching. */
+	index_delete_prefetch_buffer(rel, &prefetch_state, prefetch_distance);
+#endif
+
+	/* Iterate over deltids, determine which to delete, check their horizon */
+	Assert(delstate->ndeltids > 0);
+	for (int i = 0; i < delstate->ndeltids; i++)
+	{
+		TM_IndexDelete *ideltid = &delstate->deltids[i];
+		TM_IndexStatus *istatus = delstate->status + ideltid->id;
+		ItemPointer htid = &ideltid->tid;
+		OffsetNumber offnum;
+
+		/*
+		 * Read buffer, and perform required extra steps each time a new block
+		 * is encountered.  Avoid refetching if it's the same block as the one
+		 * from the last htid.
+		 */
+		if (blkno == InvalidBlockNumber ||
+			ItemPointerGetBlockNumber(htid) != blkno)
+		{
+			/*
+			 * Consider giving up early for bottom-up index deletion caller
+			 * first. (Only prefetch next-next block afterwards, when it
+			 * becomes clear that we're at least going to access the next
+			 * block in line.)
+			 *
+			 * Sometimes the first block frees so much space for bottom-up
+			 * caller that the deletion process can end without accessing any
+			 * more blocks.  It is usually necessary to access 2 or 3 blocks
+			 * per bottom-up deletion operation, though.
+			 */
+			if (delstate->bottomup)
+			{
+				/*
+				 * We often allow caller to delete a few additional items
+				 * whose entries we reached after the point that space target
+				 * from caller was satisfied.  The cost of accessing the page
+				 * was already paid at that point, so it made sense to finish
+				 * it off.  When that happened, we finalize everything here
+				 * (by finishing off the whole bottom-up deletion operation
+				 * without needlessly paying the cost of accessing any more
+				 * blocks).
+				 */
+				if (bottomup_final_block)
+					break;
+
+				/*
+				 * Give up when we didn't enable our caller to free any
+				 * additional space as a result of processing the page that we
+				 * just finished up with.  This rule is the main way in which
+				 * we keep the cost of bottom-up deletion under control.
+				 */
+				if (nblocksaccessed >= 1 && actualfreespace == lastfreespace)
+					break;
+				lastfreespace = actualfreespace;	/* for next time */
+
+				/*
+				 * Deletion operation (which is bottom-up) will definitely
+				 * access the next block in line.  Prepare for that now.
+				 *
+				 * Decay target free space so that we don't hang on for too
+				 * long with a marginal case. (Space target is only truly
+				 * helpful when it allows us to recognize that we don't need
+				 * to access more than 1 or 2 blocks to satisfy caller due to
+				 * agreeable workload characteristics.)
+				 *
+				 * We are a bit more patient when we encounter contiguous
+				 * blocks, though: these are treated as favorable blocks.  The
+				 * decay process is only applied when the next block in line
+				 * is not a favorable/contiguous block.  This is not an
+				 * exception to the general rule; we still insist on finding
+				 * at least one deletable item per block accessed.  See
+				 * bottomup_nblocksfavorable() for full details of the theory
+				 * behind favorable blocks and heap block locality in general.
+				 *
+				 * Note: The first block in line is always treated as a
+				 * favorable block, so the earliest possible point that the
+				 * decay can be applied is just before we access the second
+				 * block in line.  The Assert() verifies this for us.
+				 */
+				Assert(nblocksaccessed > 0 || nblocksfavorable > 0);
+				if (nblocksfavorable > 0)
+					nblocksfavorable--;
+				else
+					curtargetfreespace /= 2;
+			}
+
+			/* release old buffer */
+			if (BufferIsValid(buf))
+				UnlockReleaseBuffer(buf);
+
+			blkno = ItemPointerGetBlockNumber(htid);
+			buf = ReadBuffer(rel, blkno);
+			nblocksaccessed++;
+			Assert(!delstate->bottomup ||
+				   nblocksaccessed <= BOTTOMUP_MAX_NBLOCKS);
+
+#ifdef USE_PREFETCH
+
+			/*
+			 * To maintain the prefetch distance, prefetch one more page for
+			 * each page we read.
+			 */
+			index_delete_prefetch_buffer(rel, &prefetch_state, 1);
+#endif
+
+			LockBuffer(buf, BUFFER_LOCK_SHARE);
+
+			page = BufferGetPage(buf);
+			maxoff = PageGetMaxOffsetNumber(page);
+		}
+
+		/*
+		 * In passing, detect index corruption involving an index page with a
+		 * TID that points to a location in the heap that couldn't possibly be
+		 * correct.  We only do this with actual TIDs from caller's index page
+		 * (not items reached by traversing through a HOT chain).
+		 */
+		index_delete_check_htid(delstate, page, maxoff, htid, istatus);
+
+		if (istatus->knowndeletable)
+			Assert(!delstate->bottomup && !istatus->promising);
+		else
+		{
+			ItemPointerData tmp = *htid;
+			HeapTupleData heapTuple;
+
+			/* Are any tuples from this HOT chain non-vacuumable? */
+			if (heap_hot_search_buffer(&tmp, rel, buf, &SnapshotNonVacuumable,
+									   &heapTuple, NULL, true))
+				continue;		/* can't delete entry */
+
+			/* Caller will delete, since whole HOT chain is vacuumable */
+			istatus->knowndeletable = true;
+
+			/* Maintain index free space info for bottom-up deletion case */
+			if (delstate->bottomup)
+			{
+				Assert(istatus->freespace > 0);
+				actualfreespace += istatus->freespace;
+				if (actualfreespace >= curtargetfreespace)
+					bottomup_final_block = true;
+			}
+		}
+
+		/*
+		 * Maintain latestRemovedXid value for deletion operation as a whole
+		 * by advancing current value using heap tuple headers.  This is
+		 * loosely based on the logic for pruning a HOT chain.
+		 */
+		offnum = ItemPointerGetOffsetNumber(htid);
+		priorXmax = InvalidTransactionId;	/* cannot check first XMIN */
+		for (;;)
+		{
+			ItemId		lp;
+			HeapTupleHeader htup;
+
+			/* Sanity check (pure paranoia) */
+			if (offnum < FirstOffsetNumber)
+				break;
+
+			/*
+			 * An offset past the end of page's line pointer array is possible
+			 * when the array was truncated
+			 */
+			if (offnum > maxoff)
+				break;
+
+			lp = PageGetItemId(page, offnum);
+			if (ItemIdIsRedirected(lp))
+			{
+				offnum = ItemIdGetRedirect(lp);
+				continue;
+			}
+
+			/*
+			 * We'll often encounter LP_DEAD line pointers (especially with an
+			 * entry marked knowndeletable by our caller up front).  No heap
+			 * tuple headers get examined for an htid that leads us to an
+			 * LP_DEAD item.  This is okay because the earlier pruning
+			 * operation that made the line pointer LP_DEAD in the first place
+			 * must have considered the original tuple header as part of
+			 * generating its own latestRemovedXid value.
+			 *
+			 * Relying on XLOG_HEAP2_PRUNE records like this is the same
+			 * strategy that index vacuuming uses in all cases.  Index VACUUM
+			 * WAL records don't even have a latestRemovedXid field of their
+			 * own for this reason.
+			 */
+			if (!ItemIdIsNormal(lp))
+				break;
+
+			htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+			/*
+			 * Check the tuple XMIN against prior XMAX, if any
+			 */
+			if (TransactionIdIsValid(priorXmax) &&
+				!TransactionIdEquals(HeapTupleHeaderGetXmin(htup), priorXmax))
+				break;
+
+			HeapTupleHeaderAdvanceLatestRemovedXid(htup, &latestRemovedXid);
+
+			/*
+			 * If the tuple is not HOT-updated, then we are at the end of this
+			 * HOT-chain.  No need to visit later tuples from the same update
+			 * chain (they get their own index entries) -- just move on to
+			 * next htid from index AM caller.
+			 */
+			if (!HeapTupleHeaderIsHotUpdated(htup))
+				break;
+
+			/* Advance to next HOT chain member */
+			Assert(ItemPointerGetBlockNumber(&htup->t_ctid) == blkno);
+			offnum = ItemPointerGetOffsetNumber(&htup->t_ctid);
+			priorXmax = HeapTupleHeaderGetUpdateXid(htup);
+		}
+
+		/* Enable further/final shrinking of deltids for caller */
+		finalndeltids = i + 1;
+	}
+
+	UnlockReleaseBuffer(buf);
+
+	/*
+	 * Shrink deltids array to exclude non-deletable entries at the end.  This
+	 * is not just a minor optimization.  Final deltids array size might be
+	 * zero for a bottom-up caller.  Index AM is explicitly allowed to rely on
+	 * ndeltids being zero in all cases with zero total deletable entries.
+	 */
+	Assert(finalndeltids > 0 || delstate->bottomup);
+	delstate->ndeltids = finalndeltids;
+
+	return latestRemovedXid;
+}
+
+/*
+ * Specialized inlineable comparison function for index_delete_sort()
+ */
+static inline int
+index_delete_sort_cmp(TM_IndexDelete *deltid1, TM_IndexDelete *deltid2)
+{
+	ItemPointer tid1 = &deltid1->tid;
+	ItemPointer tid2 = &deltid2->tid;
+
+	{
+		BlockNumber blk1 = ItemPointerGetBlockNumber(tid1);
+		BlockNumber blk2 = ItemPointerGetBlockNumber(tid2);
+
+		if (blk1 != blk2)
+			return (blk1 < blk2) ? -1 : 1;
+	}
+	{
+		OffsetNumber pos1 = ItemPointerGetOffsetNumber(tid1);
+		OffsetNumber pos2 = ItemPointerGetOffsetNumber(tid2);
+
+		if (pos1 != pos2)
+			return (pos1 < pos2) ? -1 : 1;
+	}
+
+	Assert(false);
+
+	return 0;
+}
+
+/*
+ * Sort deltids array from delstate by TID.  This prepares it for further
+ * processing by heap_index_delete_tuples().
+ *
+ * This operation becomes a noticeable consumer of CPU cycles with some
+ * workloads, so we go to the trouble of specialization/micro optimization.
+ * We use shellsort for this because it's easy to specialize, compiles to
+ * relatively few instructions, and is adaptive to presorted inputs/subsets
+ * (which are typical here).
+ */
+static void
+index_delete_sort(TM_IndexDeleteOp *delstate)
+{
+	TM_IndexDelete *deltids = delstate->deltids;
+	int			ndeltids = delstate->ndeltids;
+	int			low = 0;
+
+	/*
+	 * Shellsort gap sequence (taken from Sedgewick-Incerpi paper).
+	 *
+	 * This implementation is fast with array sizes up to ~4500.  This covers
+	 * all supported BLCKSZ values.
+	 */
+	const int	gaps[9] = {1968, 861, 336, 112, 48, 21, 7, 3, 1};
+
+	/* Think carefully before changing anything here -- keep swaps cheap */
+	StaticAssertStmt(sizeof(TM_IndexDelete) <= 8,
+					 "element size exceeds 8 bytes");
+
+	for (int g = 0; g < lengthof(gaps); g++)
+	{
+		for (int hi = gaps[g], i = low + hi; i < ndeltids; i++)
+		{
+			TM_IndexDelete d = deltids[i];
+			int			j = i;
+
+			while (j >= hi && index_delete_sort_cmp(&deltids[j - hi], &d) >= 0)
+			{
+				deltids[j] = deltids[j - hi];
+				j -= hi;
+			}
+			deltids[j] = d;
+		}
+	}
+}
+
+/*
+ * Returns how many blocks should be considered favorable/contiguous for a
+ * bottom-up index deletion pass.  This is a number of heap blocks that starts
+ * from and includes the first block in line.
+ *
+ * There is always at least one favorable block during bottom-up index
+ * deletion.  In the worst case (i.e. with totally random heap blocks) the
+ * first block in line (the only favorable block) can be thought of as a
+ * degenerate array of contiguous blocks that consists of a single block.
+ * heap_index_delete_tuples() will expect this.
+ *
+ * Caller passes blockgroups, a description of the final order that deltids
+ * will be sorted in for heap_index_delete_tuples() bottom-up index deletion
+ * processing.  Note that deltids need not actually be sorted just yet (caller
+ * only passes deltids to us so that we can interpret blockgroups).
+ *
+ * You might guess that the existence of contiguous blocks cannot matter much,
+ * since in general the main factor that determines which blocks we visit is
+ * the number of promising TIDs, which is a fixed hint from the index AM.
+ * We're not really targeting the general case, though -- the actual goal is
+ * to adapt our behavior to a wide variety of naturally occurring conditions.
+ * The effects of most of the heuristics we apply are only noticeable in the
+ * aggregate, over time and across many _related_ bottom-up index deletion
+ * passes.
+ *
+ * Deeming certain blocks favorable allows heapam to recognize and adapt to
+ * workloads where heap blocks visited during bottom-up index deletion can be
+ * accessed contiguously, in the sense that each newly visited block is the
+ * neighbor of the block that bottom-up deletion just finished processing (or
+ * close enough to it).  It will likely be cheaper to access more favorable
+ * blocks sooner rather than later (e.g. in this pass, not across a series of
+ * related bottom-up passes).  Either way it is probably only a matter of time
+ * (or a matter of further correlated version churn) before all blocks that
+ * appear together as a single large batch of favorable blocks get accessed by
+ * _some_ bottom-up pass.  Large batches of favorable blocks tend to either
+ * appear almost constantly or not even once (it all depends on per-index
+ * workload characteristics).
+ *
+ * Note that the blockgroups sort order applies a power-of-two bucketing
+ * scheme that creates opportunities for contiguous groups of blocks to get
+ * batched together, at least with workloads that are naturally amenable to
+ * being driven by heap block locality.  This doesn't just enhance the spatial
+ * locality of bottom-up heap block processing in the obvious way.  It also
+ * enables temporal locality of access, since sorting by heap block number
+ * naturally tends to make the bottom-up processing order deterministic.
+ *
+ * Consider the following example to get a sense of how temporal locality
+ * might matter: There is a heap relation with several indexes, each of which
+ * is low to medium cardinality.  It is subject to constant non-HOT updates.
+ * The updates are skewed (in one part of the primary key, perhaps).  None of
+ * the indexes are logically modified by the UPDATE statements (if they were
+ * then bottom-up index deletion would not be triggered in the first place).
+ * Naturally, each new round of index tuples (for each heap tuple that gets a
+ * heap_update() call) will have the same heap TID in each and every index.
+ * Since these indexes are low cardinality and never get logically modified,
+ * heapam processing during bottom-up deletion passes will access heap blocks
+ * in approximately sequential order.  Temporal locality of access occurs due
+ * to bottom-up deletion passes behaving very similarly across each of the
+ * indexes at any given moment.  This keeps the number of buffer misses needed
+ * to visit heap blocks to a minimum.
+ */
+static int
+bottomup_nblocksfavorable(IndexDeleteCounts *blockgroups, int nblockgroups,
+						  TM_IndexDelete *deltids)
+{
+	int64		lastblock = -1;
+	int			nblocksfavorable = 0;
+
+	Assert(nblockgroups >= 1);
+	Assert(nblockgroups <= BOTTOMUP_MAX_NBLOCKS);
+
+	/*
+	 * We tolerate heap blocks that will be accessed only slightly out of
+	 * physical order.  Small blips occur when a pair of almost-contiguous
+	 * blocks happen to fall into different buckets (perhaps due only to a
+	 * small difference in npromisingtids that the bucketing scheme didn't
+	 * quite manage to ignore).  We effectively ignore these blips by applying
+	 * a small tolerance.  The precise tolerance we use is a little arbitrary,
+	 * but it works well enough in practice.
+	 */
+	for (int b = 0; b < nblockgroups; b++)
+	{
+		IndexDeleteCounts *group = blockgroups + b;
+		TM_IndexDelete *firstdtid = deltids + group->ifirsttid;
+		BlockNumber block = ItemPointerGetBlockNumber(&firstdtid->tid);
+
+		if (lastblock != -1 &&
+			((int64) block < lastblock - BOTTOMUP_TOLERANCE_NBLOCKS ||
+			 (int64) block > lastblock + BOTTOMUP_TOLERANCE_NBLOCKS))
+			break;
+
+		nblocksfavorable++;
+		lastblock = block;
+	}
+
+	/* Always indicate that there is at least 1 favorable block */
+	Assert(nblocksfavorable >= 1);
+
+	return nblocksfavorable;
+}
+
+/*
+ * qsort comparison function for bottomup_sort_and_shrink()
+ */
+static int
+bottomup_sort_and_shrink_cmp(const void *arg1, const void *arg2)
+{
+	const IndexDeleteCounts *group1 = (const IndexDeleteCounts *) arg1;
+	const IndexDeleteCounts *group2 = (const IndexDeleteCounts *) arg2;
+
+	/*
+	 * Most significant field is npromisingtids (which we invert the order of
+	 * so as to sort in desc order).
+	 *
+	 * Caller should have already normalized npromisingtids fields into
+	 * power-of-two values (buckets).
+	 */
+	if (group1->npromisingtids > group2->npromisingtids)
+		return -1;
+	if (group1->npromisingtids < group2->npromisingtids)
+		return 1;
+
+	/*
+	 * Tiebreak: desc ntids sort order.
+	 *
+	 * We cannot expect power-of-two values for ntids fields.  We should
+	 * behave as if they were already rounded up for us instead.
+	 */
+	if (group1->ntids != group2->ntids)
+	{
+		uint32		ntids1 = pg_nextpower2_32((uint32) group1->ntids);
+		uint32		ntids2 = pg_nextpower2_32((uint32) group2->ntids);
+
+		if (ntids1 > ntids2)
+			return -1;
+		if (ntids1 < ntids2)
+			return 1;
+	}
+
+	/*
+	 * Tiebreak: asc offset-into-deltids-for-block (offset to first TID for
+	 * block in deltids array) order.
+	 *
+	 * This is equivalent to sorting in ascending heap block number order
+	 * (among otherwise equal subsets of the array).  This approach allows us
+	 * to avoid accessing the out-of-line TID.  (We rely on the assumption
+	 * that the deltids array was sorted in ascending heap TID order when
+	 * these offsets to the first TID from each heap block group were formed.)
+	 */
+	if (group1->ifirsttid > group2->ifirsttid)
+		return 1;
+	if (group1->ifirsttid < group2->ifirsttid)
+		return -1;
+
+	pg_unreachable();
+
+	return 0;
+}
+
+/*
+ * heap_index_delete_tuples() helper function for bottom-up deletion callers.
+ *
+ * Sorts deltids array in the order needed for useful processing by bottom-up
+ * deletion.  The array should already be sorted in TID order when we're
+ * called.  The sort process groups heap TIDs from deltids into heap block
+ * groupings.  Earlier/more-promising groups/blocks are usually those that are
+ * known to have the most "promising" TIDs.
+ *
+ * Sets new size of deltids array (ndeltids) in state.  deltids will only have
+ * TIDs from the BOTTOMUP_MAX_NBLOCKS most promising heap blocks when we
+ * return.  This often means that deltids will be shrunk to a small fraction
+ * of its original size (we eliminate many heap blocks from consideration for
+ * caller up front).
+ *
+ * Returns the number of "favorable" blocks.  See bottomup_nblocksfavorable()
+ * for a definition and full details.
+ */
+static int
+bottomup_sort_and_shrink(TM_IndexDeleteOp *delstate)
+{
+	IndexDeleteCounts *blockgroups;
+	TM_IndexDelete *reordereddeltids;
+	BlockNumber curblock = InvalidBlockNumber;
+	int			nblockgroups = 0;
+	int			ncopied = 0;
+	int			nblocksfavorable = 0;
+
+	Assert(delstate->bottomup);
+	Assert(delstate->ndeltids > 0);
+
+	/* Calculate per-heap-block count of TIDs */
+	blockgroups = palloc(sizeof(IndexDeleteCounts) * delstate->ndeltids);
+	for (int i = 0; i < delstate->ndeltids; i++)
+	{
+		TM_IndexDelete *ideltid = &delstate->deltids[i];
+		TM_IndexStatus *istatus = delstate->status + ideltid->id;
+		ItemPointer htid = &ideltid->tid;
+		bool		promising = istatus->promising;
+
+		if (curblock != ItemPointerGetBlockNumber(htid))
+		{
+			/* New block group */
+			nblockgroups++;
+
+			Assert(curblock < ItemPointerGetBlockNumber(htid) ||
+				   !BlockNumberIsValid(curblock));
+
+			curblock = ItemPointerGetBlockNumber(htid);
+			blockgroups[nblockgroups - 1].ifirsttid = i;
+			blockgroups[nblockgroups - 1].ntids = 1;
+			blockgroups[nblockgroups - 1].npromisingtids = 0;
+		}
+		else
+		{
+			blockgroups[nblockgroups - 1].ntids++;
+		}
+
+		if (promising)
+			blockgroups[nblockgroups - 1].npromisingtids++;
+	}
+
+	/*
+	 * We're about ready to sort block groups to determine the optimal order
+	 * for visiting heap blocks.  But before we do, round the number of
+	 * promising tuples for each block group up to the next power-of-two,
+	 * unless it is very low (less than 4), in which case we round up to 4.
+	 * npromisingtids is far too noisy to trust when choosing between a pair
+	 * of block groups that both have very low values.
+	 *
+	 * This scheme divides heap blocks/block groups into buckets.  Each bucket
+	 * contains blocks that have _approximately_ the same number of promising
+	 * TIDs as each other.  The goal is to ignore relatively small differences
+	 * in the total number of promising entries, so that the whole process can
+	 * give a little weight to heapam factors (like heap block locality)
+	 * instead.  This isn't a trade-off, really -- we have nothing to lose. It
+	 * would be foolish to interpret small differences in npromisingtids
+	 * values as anything more than noise.
+	 *
+	 * We tiebreak on nhtids when sorting block group subsets that have the
+	 * same npromisingtids, but this has the same issues as npromisingtids,
+	 * and so nhtids is subject to the same power-of-two bucketing scheme. The
+	 * only reason that we don't fix nhtids in the same way here too is that
+	 * we'll need accurate nhtids values after the sort.  We handle nhtids
+	 * bucketization dynamically instead (in the sort comparator).
+	 *
+	 * See bottomup_nblocksfavorable() for a full explanation of when and how
+	 * heap locality/favorable blocks can significantly influence when and how
+	 * heap blocks are accessed.
+	 */
+	for (int b = 0; b < nblockgroups; b++)
+	{
+		IndexDeleteCounts *group = blockgroups + b;
+
+		/* Better off falling back on nhtids with low npromisingtids */
+		if (group->npromisingtids <= 4)
+			group->npromisingtids = 4;
+		else
+			group->npromisingtids =
+				pg_nextpower2_32((uint32) group->npromisingtids);
+	}
+
+	/* Sort groups and rearrange caller's deltids array */
+	qsort(blockgroups, nblockgroups, sizeof(IndexDeleteCounts),
+		  bottomup_sort_and_shrink_cmp);
+	reordereddeltids = palloc(delstate->ndeltids * sizeof(TM_IndexDelete));
+
+	nblockgroups = Min(BOTTOMUP_MAX_NBLOCKS, nblockgroups);
+	/* Determine number of favorable blocks at the start of final deltids */
+	nblocksfavorable = bottomup_nblocksfavorable(blockgroups, nblockgroups,
+												 delstate->deltids);
+
+	for (int b = 0; b < nblockgroups; b++)
+	{
+		IndexDeleteCounts *group = blockgroups + b;
+		TM_IndexDelete *firstdtid = delstate->deltids + group->ifirsttid;
+
+		memcpy(reordereddeltids + ncopied, firstdtid,
+			   sizeof(TM_IndexDelete) * group->ntids);
+		ncopied += group->ntids;
+	}
+
+	/* Copy final grouped and sorted TIDs back into start of caller's array */
+	memcpy(delstate->deltids, reordereddeltids,
+		   sizeof(TM_IndexDelete) * ncopied);
+	delstate->ndeltids = ncopied;
+
+	pfree(reordereddeltids);
+	pfree(blockgroups);
+
+	return nblocksfavorable;
+}
+
+/*
+ * Perform XLogInsert for a heap-freeze operation.  Caller must have already
+ * modified the buffer and marked it dirty.
+ */
+XLogRecPtr
+log_heap_freeze(Relation reln, Buffer buffer, TransactionId cutoff_xid,
+				xl_heap_freeze_tuple *tuples, int ntuples)
+{
+	xl_heap_freeze_page xlrec;
+	XLogRecPtr	recptr;
+
+	/* Caller should not call me on a non-WAL-logged relation */
+	Assert(RelationNeedsWAL(reln));
+	/* nor when there are no tuples to freeze */
+	Assert(ntuples > 0);
+
+	xlrec.cutoff_xid = cutoff_xid;
+	xlrec.ntuples = ntuples;
+
+	XLogBeginInsert();
+	XLogRegisterData((char *) &xlrec, SizeOfHeapFreezePage);
+
+	/*
+	 * The freeze plan array is not actually in the buffer, but pretend that
+	 * it is.  When XLogInsert stores the whole buffer, the freeze plan need
+	 * not be stored too.
+	 */
+	XLogRegisterBuffer(0, buffer, REGBUF_STANDARD);
+	XLogRegisterBufData(0, (char *) tuples,
+						ntuples * sizeof(xl_heap_freeze_tuple));
+
+	recptr = XLogInsert(RM_HEAP2_ID, XLOG_HEAP2_FREEZE_PAGE);
+
+	return recptr;
+}
+
+/*
+ * Perform XLogInsert for a heap-visible operation.  'block' is the block
+ * being marked all-visible, and vm_buffer is the buffer containing the
+ * corresponding visibility map block.  Both should have already been modified
+ * and dirtied.
+ *
+ * If checksums are enabled, we also generate a full-page image of
+ * heap_buffer, if necessary.
+ */
+XLogRecPtr
+log_heap_visible(RelFileNode rnode, Buffer heap_buffer, Buffer vm_buffer,
+				 TransactionId cutoff_xid, uint8 vmflags)
+{
+	xl_heap_visible xlrec;
+	XLogRecPtr	recptr;
+	uint8		flags;
+
+	Assert(BufferIsValid(heap_buffer));
+	Assert(BufferIsValid(vm_buffer));
+
+	xlrec.cutoff_xid = cutoff_xid;
+	xlrec.flags = vmflags;
+	XLogBeginInsert();
+	XLogRegisterData((char *) &xlrec, SizeOfHeapVisible);
+
+	XLogRegisterBuffer(0, vm_buffer, 0);
+
+	flags = REGBUF_STANDARD;
+	if (!XLogHintBitIsNeeded())
+		flags |= REGBUF_NO_IMAGE;
+	XLogRegisterBuffer(1, heap_buffer, flags);
+
+	recptr = XLogInsert(RM_HEAP2_ID, XLOG_HEAP2_VISIBLE);
+
+	return recptr;
+}
+
+/*
+ * Perform XLogInsert for a heap-update operation.  Caller must already
+ * have modified the buffer(s) and marked them dirty.
+ */
+static XLogRecPtr
+log_heap_update(Relation reln, Buffer oldbuf,
+				Buffer newbuf, HeapTuple oldtup, HeapTuple newtup,
+				HeapTuple old_key_tuple,
+				bool all_visible_cleared, bool new_all_visible_cleared)
+{
+	xl_heap_update xlrec;
+	xl_heap_header xlhdr;
+	xl_heap_header xlhdr_idx;
+	uint8		info;
+	uint16		prefix_suffix[2];
+	uint16		prefixlen = 0,
+				suffixlen = 0;
+	XLogRecPtr	recptr;
+	Page		page = BufferGetPage(newbuf);
+	bool		need_tuple_data = RelationIsLogicallyLogged(reln);
+	bool		init;
+	int			bufflags;
+
+	/* Caller should not call me on a non-WAL-logged relation */
+	Assert(RelationNeedsWAL(reln));
+
+	XLogBeginInsert();
+
+	if (HeapTupleIsHeapOnly(newtup))
+		info = XLOG_HEAP_HOT_UPDATE;
+	else
+		info = XLOG_HEAP_UPDATE;
+
+	/*
+	 * If the old and new tuple are on the same page, we only need to log the
+	 * parts of the new tuple that were changed.  That saves on the amount of
+	 * WAL we need to write.  Currently, we just count any unchanged bytes in
+	 * the beginning and end of the tuple.  That's quick to check, and
+	 * perfectly covers the common case that only one field is updated.
+	 *
+	 * We could do this even if the old and new tuple are on different pages,
+	 * but only if we don't make a full-page image of the old page, which is
+	 * difficult to know in advance.  Also, if the old tuple is corrupt for
+	 * some reason, it would allow the corruption to propagate the new page,
+	 * so it seems best to avoid.  Under the general assumption that most
+	 * updates tend to create the new tuple version on the same page, there
+	 * isn't much to be gained by doing this across pages anyway.
+	 *
+	 * Skip this if we're taking a full-page image of the new page, as we
+	 * don't include the new tuple in the WAL record in that case.  Also
+	 * disable if wal_level='logical', as logical decoding needs to be able to
+	 * read the new tuple in whole from the WAL record alone.
+	 */
+	if (oldbuf == newbuf && !need_tuple_data &&
+		!XLogCheckBufferNeedsBackup(newbuf))
+	{
+		char	   *oldp = (char *) oldtup->t_data + oldtup->t_data->t_hoff;
+		char	   *newp = (char *) newtup->t_data + newtup->t_data->t_hoff;
+		int			oldlen = oldtup->t_len - oldtup->t_data->t_hoff;
+		int			newlen = newtup->t_len - newtup->t_data->t_hoff;
+
+		/* Check for common prefix between old and new tuple */
+		for (prefixlen = 0; prefixlen < Min(oldlen, newlen); prefixlen++)
+		{
+			if (newp[prefixlen] != oldp[prefixlen])
+				break;
+		}
+
+		/*
+		 * Storing the length of the prefix takes 2 bytes, so we need to save
+		 * at least 3 bytes or there's no point.
+		 */
+		if (prefixlen < 3)
+			prefixlen = 0;
+
+		/* Same for suffix */
+		for (suffixlen = 0; suffixlen < Min(oldlen, newlen) - prefixlen; suffixlen++)
+		{
+			if (newp[newlen - suffixlen - 1] != oldp[oldlen - suffixlen - 1])
+				break;
+		}
+		if (suffixlen < 3)
+			suffixlen = 0;
+	}
+
+	/* Prepare main WAL data chain */
+	xlrec.flags = 0;
+	if (all_visible_cleared)
+		xlrec.flags |= XLH_UPDATE_OLD_ALL_VISIBLE_CLEARED;
+	if (new_all_visible_cleared)
+		xlrec.flags |= XLH_UPDATE_NEW_ALL_VISIBLE_CLEARED;
+	if (prefixlen > 0)
+		xlrec.flags |= XLH_UPDATE_PREFIX_FROM_OLD;
+	if (suffixlen > 0)
+		xlrec.flags |= XLH_UPDATE_SUFFIX_FROM_OLD;
+	if (need_tuple_data)
+	{
+		xlrec.flags |= XLH_UPDATE_CONTAINS_NEW_TUPLE;
+		if (old_key_tuple)
+		{
+			if (reln->rd_rel->relreplident == REPLICA_IDENTITY_FULL)
+				xlrec.flags |= XLH_UPDATE_CONTAINS_OLD_TUPLE;
+			else
+				xlrec.flags |= XLH_UPDATE_CONTAINS_OLD_KEY;
+		}
+	}
+
+	/* If new tuple is the single and first tuple on page... */
+	if (ItemPointerGetOffsetNumber(&(newtup->t_self)) == FirstOffsetNumber &&
+		PageGetMaxOffsetNumber(page) == FirstOffsetNumber)
+	{
+		info |= XLOG_HEAP_INIT_PAGE;
+		init = true;
+	}
+	else
+		init = false;
+
+	/* Prepare WAL data for the old page */
+	xlrec.old_offnum = ItemPointerGetOffsetNumber(&oldtup->t_self);
+	xlrec.old_xmax = HeapTupleHeaderGetRawXmax(oldtup->t_data);
+	xlrec.old_infobits_set = compute_infobits(oldtup->t_data->t_infomask,
+											  oldtup->t_data->t_infomask2);
+
+	/* Prepare WAL data for the new page */
+	xlrec.new_offnum = ItemPointerGetOffsetNumber(&newtup->t_self);
+	xlrec.new_xmax = HeapTupleHeaderGetRawXmax(newtup->t_data);
+
+	bufflags = REGBUF_STANDARD;
+	if (init)
+		bufflags |= REGBUF_WILL_INIT;
+	if (need_tuple_data)
+		bufflags |= REGBUF_KEEP_DATA;
+
+	XLogRegisterBuffer(0, newbuf, bufflags);
+	if (oldbuf != newbuf)
+		XLogRegisterBuffer(1, oldbuf, REGBUF_STANDARD);
+
+	XLogRegisterData((char *) &xlrec, SizeOfHeapUpdate);
+
+	/*
+	 * Prepare WAL data for the new tuple.
+	 */
+	if (prefixlen > 0 || suffixlen > 0)
+	{
+		if (prefixlen > 0 && suffixlen > 0)
+		{
+			prefix_suffix[0] = prefixlen;
+			prefix_suffix[1] = suffixlen;
+			XLogRegisterBufData(0, (char *) &prefix_suffix, sizeof(uint16) * 2);
+		}
+		else if (prefixlen > 0)
+		{
+			XLogRegisterBufData(0, (char *) &prefixlen, sizeof(uint16));
+		}
+		else
+		{
+			XLogRegisterBufData(0, (char *) &suffixlen, sizeof(uint16));
+		}
+	}
+
+	xlhdr.t_infomask2 = newtup->t_data->t_infomask2;
+	xlhdr.t_infomask = newtup->t_data->t_infomask;
+	xlhdr.t_hoff = newtup->t_data->t_hoff;
+	Assert(SizeofHeapTupleHeader + prefixlen + suffixlen <= newtup->t_len);
+
+	/*
+	 * PG73FORMAT: write bitmap [+ padding] [+ oid] + data
+	 *
+	 * The 'data' doesn't include the common prefix or suffix.
+	 */
+	XLogRegisterBufData(0, (char *) &xlhdr, SizeOfHeapHeader);
+	if (prefixlen == 0)
+	{
+		XLogRegisterBufData(0,
+							((char *) newtup->t_data) + SizeofHeapTupleHeader,
+							newtup->t_len - SizeofHeapTupleHeader - suffixlen);
+	}
+	else
+	{
+		/*
+		 * Have to write the null bitmap and data after the common prefix as
+		 * two separate rdata entries.
+		 */
+		/* bitmap [+ padding] [+ oid] */
+		if (newtup->t_data->t_hoff - SizeofHeapTupleHeader > 0)
+		{
+			XLogRegisterBufData(0,
+								((char *) newtup->t_data) + SizeofHeapTupleHeader,
+								newtup->t_data->t_hoff - SizeofHeapTupleHeader);
+		}
+
+		/* data after common prefix */
+		XLogRegisterBufData(0,
+							((char *) newtup->t_data) + newtup->t_data->t_hoff + prefixlen,
+							newtup->t_len - newtup->t_data->t_hoff - prefixlen - suffixlen);
+	}
+
+	/* We need to log a tuple identity */
+	if (need_tuple_data && old_key_tuple)
+	{
+		/* don't really need this, but its more comfy to decode */
+		xlhdr_idx.t_infomask2 = old_key_tuple->t_data->t_infomask2;
+		xlhdr_idx.t_infomask = old_key_tuple->t_data->t_infomask;
+		xlhdr_idx.t_hoff = old_key_tuple->t_data->t_hoff;
+
+		XLogRegisterData((char *) &xlhdr_idx, SizeOfHeapHeader);
+
+		/* PG73FORMAT: write bitmap [+ padding] [+ oid] + data */
+		XLogRegisterData((char *) old_key_tuple->t_data + SizeofHeapTupleHeader,
+						 old_key_tuple->t_len - SizeofHeapTupleHeader);
+	}
+
+	/* filtering by origin on a row level is much more efficient */
+	XLogSetRecordFlags(XLOG_INCLUDE_ORIGIN);
+
+	recptr = XLogInsert(RM_HEAP_ID, info);
+
+	return recptr;
+}
+
+/*
+ * Perform XLogInsert of an XLOG_HEAP2_NEW_CID record
+ *
+ * This is only used in wal_level >= WAL_LEVEL_LOGICAL, and only for catalog
+ * tuples.
+ */
+static XLogRecPtr
+log_heap_new_cid(Relation relation, HeapTuple tup)
+{
+	xl_heap_new_cid xlrec;
+
+	XLogRecPtr	recptr;
+	HeapTupleHeader hdr = tup->t_data;
+
+	Assert(ItemPointerIsValid(&tup->t_self));
+	Assert(tup->t_tableOid != InvalidOid);
+
+	xlrec.top_xid = GetTopTransactionId();
+	xlrec.target_node = relation->rd_node;
+	xlrec.target_tid = tup->t_self;
+
+	/*
+	 * If the tuple got inserted & deleted in the same TX we definitely have a
+	 * combo CID, set cmin and cmax.
+	 */
+	if (hdr->t_infomask & HEAP_COMBOCID)
+	{
+		Assert(!(hdr->t_infomask & HEAP_XMAX_INVALID));
+		Assert(!HeapTupleHeaderXminInvalid(hdr));
+		xlrec.cmin = HeapTupleHeaderGetCmin(hdr);
+		xlrec.cmax = HeapTupleHeaderGetCmax(hdr);
+		xlrec.combocid = HeapTupleHeaderGetRawCommandId(hdr);
+	}
+	/* No combo CID, so only cmin or cmax can be set by this TX */
+	else
+	{
+		/*
+		 * Tuple inserted.
+		 *
+		 * We need to check for LOCK ONLY because multixacts might be
+		 * transferred to the new tuple in case of FOR KEY SHARE updates in
+		 * which case there will be an xmax, although the tuple just got
+		 * inserted.
+		 */
+		if (hdr->t_infomask & HEAP_XMAX_INVALID ||
+			HEAP_XMAX_IS_LOCKED_ONLY(hdr->t_infomask))
+		{
+			xlrec.cmin = HeapTupleHeaderGetRawCommandId(hdr);
+			xlrec.cmax = InvalidCommandId;
+		}
+		/* Tuple from a different tx updated or deleted. */
+		else
+		{
+			xlrec.cmin = InvalidCommandId;
+			xlrec.cmax = HeapTupleHeaderGetRawCommandId(hdr);
+		}
+		xlrec.combocid = InvalidCommandId;
+	}
+
+	/*
+	 * Note that we don't need to register the buffer here, because this
+	 * operation does not modify the page. The insert/update/delete that
+	 * called us certainly did, but that's WAL-logged separately.
+	 */
+	XLogBeginInsert();
+	XLogRegisterData((char *) &xlrec, SizeOfHeapNewCid);
+
+	/* will be looked at irrespective of origin */
+
+	recptr = XLogInsert(RM_HEAP2_ID, XLOG_HEAP2_NEW_CID);
+
+	return recptr;
+}
+
+/*
+ * Build a heap tuple representing the configured REPLICA IDENTITY to represent
+ * the old tuple in an UPDATE or DELETE.
+ *
+ * Returns NULL if there's no need to log an identity or if there's no suitable
+ * key defined.
+ *
+ * Pass key_required true if any replica identity columns changed value, or if
+ * any of them have any external data.  Delete must always pass true.
+ *
+ * *copy is set to true if the returned tuple is a modified copy rather than
+ * the same tuple that was passed in.
+ */
+static HeapTuple
+ExtractReplicaIdentity(Relation relation, HeapTuple tp, bool key_required,
+					   bool *copy)
+{
+	TupleDesc	desc = RelationGetDescr(relation);
+	char		replident = relation->rd_rel->relreplident;
+	Bitmapset  *idattrs;
+	HeapTuple	key_tuple;
+	bool		nulls[MaxHeapAttributeNumber];
+	Datum		values[MaxHeapAttributeNumber];
+
+	*copy = false;
+
+	if (!RelationIsLogicallyLogged(relation))
+		return NULL;
+
+	if (replident == REPLICA_IDENTITY_NOTHING)
+		return NULL;
+
+	if (replident == REPLICA_IDENTITY_FULL)
+	{
+		/*
+		 * When logging the entire old tuple, it very well could contain
+		 * toasted columns. If so, force them to be inlined.
+		 */
+		if (HeapTupleHasExternal(tp))
+		{
+			*copy = true;
+			tp = toast_flatten_tuple(tp, desc);
+		}
+		return tp;
+	}
+
+	/* if the key isn't required and we're only logging the key, we're done */
+	if (!key_required)
+		return NULL;
+
+	/* find out the replica identity columns */
+	idattrs = RelationGetIndexAttrBitmap(relation,
+										 INDEX_ATTR_BITMAP_IDENTITY_KEY);
+
+	/*
+	 * If there's no defined replica identity columns, treat as !key_required.
+	 * (This case should not be reachable from heap_update, since that should
+	 * calculate key_required accurately.  But heap_delete just passes
+	 * constant true for key_required, so we can hit this case in deletes.)
+	 */
+	if (bms_is_empty(idattrs))
+		return NULL;
+
+	/*
+	 * Construct a new tuple containing only the replica identity columns,
+	 * with nulls elsewhere.  While we're at it, assert that the replica
+	 * identity columns aren't null.
+	 */
+	heap_deform_tuple(tp, desc, values, nulls);
+
+	for (int i = 0; i < desc->natts; i++)
+	{
+		if (bms_is_member(i + 1 - FirstLowInvalidHeapAttributeNumber,
+						  idattrs))
+			Assert(!nulls[i]);
+		else
+			nulls[i] = true;
+	}
+
+	key_tuple = heap_form_tuple(desc, values, nulls);
+	*copy = true;
+
+	bms_free(idattrs);
+
+	/*
+	 * If the tuple, which by here only contains indexed columns, still has
+	 * toasted columns, force them to be inlined. This is somewhat unlikely
+	 * since there's limits on the size of indexed columns, so we don't
+	 * duplicate toast_flatten_tuple()s functionality in the above loop over
+	 * the indexed columns, even if it would be more efficient.
+	 */
+	if (HeapTupleHasExternal(key_tuple))
+	{
+		HeapTuple	oldtup = key_tuple;
+
+		key_tuple = toast_flatten_tuple(oldtup, desc);
+		heap_freetuple(oldtup);
+	}
+
+	return key_tuple;
+}
+
+/*
+ * Handles XLOG_HEAP2_PRUNE record type.
+ *
+ * Acquires a full cleanup lock.
+ */
+static void
+heap_xlog_prune(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_prune *xlrec = (xl_heap_prune *) XLogRecGetData(record);
+	Buffer		buffer;
+	RelFileNode rnode;
+	BlockNumber blkno;
+	XLogRedoAction action;
+
+	XLogRecGetBlockTag(record, 0, &rnode, NULL, &blkno);
+
+	/*
+	 * We're about to remove tuples. In Hot Standby mode, ensure that there's
+	 * no queries running for which the removed tuples are still visible.
+	 */
+	if (InHotStandby)
+		ResolveRecoveryConflictWithSnapshot(xlrec->latestRemovedXid, rnode);
+
+	/*
+	 * If we have a full-page image, restore it (using a cleanup lock) and
+	 * we're done.
+	 */
+	action = XLogReadBufferForRedoExtended(record, 0, RBM_NORMAL, true,
+										   &buffer);
+	if (action == BLK_NEEDS_REDO)
+	{
+		Page		page = (Page) BufferGetPage(buffer);
+		OffsetNumber *end;
+		OffsetNumber *redirected;
+		OffsetNumber *nowdead;
+		OffsetNumber *nowunused;
+		int			nredirected;
+		int			ndead;
+		int			nunused;
+		Size		datalen;
+
+		redirected = (OffsetNumber *) XLogRecGetBlockData(record, 0, &datalen);
+
+		nredirected = xlrec->nredirected;
+		ndead = xlrec->ndead;
+		end = (OffsetNumber *) ((char *) redirected + datalen);
+		nowdead = redirected + (nredirected * 2);
+		nowunused = nowdead + ndead;
+		nunused = (end - nowunused);
+		Assert(nunused >= 0);
+
+		/* Update all line pointers per the record, and repair fragmentation */
+		heap_page_prune_execute(buffer,
+								redirected, nredirected,
+								nowdead, ndead,
+								nowunused, nunused);
+
+		/*
+		 * Note: we don't worry about updating the page's prunability hints.
+		 * At worst this will cause an extra prune cycle to occur soon.
+		 */
+
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(buffer);
+	}
+
+	if (BufferIsValid(buffer))
+	{
+		Size		freespace = PageGetHeapFreeSpace(BufferGetPage(buffer));
+
+		UnlockReleaseBuffer(buffer);
+
+		/*
+		 * After pruning records from a page, it's useful to update the FSM
+		 * about it, as it may cause the page become target for insertions
+		 * later even if vacuum decides not to visit it (which is possible if
+		 * gets marked all-visible.)
+		 *
+		 * Do this regardless of a full-page image being applied, since the
+		 * FSM data is not in the page anyway.
+		 */
+		XLogRecordPageWithFreeSpace(rnode, blkno, freespace);
+	}
+}
+
+/*
+ * Handles XLOG_HEAP2_VACUUM record type.
+ *
+ * Acquires an ordinary exclusive lock only.
+ */
+static void
+heap_xlog_vacuum(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_vacuum *xlrec = (xl_heap_vacuum *) XLogRecGetData(record);
+	Buffer		buffer;
+	BlockNumber blkno;
+	XLogRedoAction action;
+
+	/*
+	 * If we have a full-page image, restore it	(without using a cleanup lock)
+	 * and we're done.
+	 */
+	action = XLogReadBufferForRedoExtended(record, 0, RBM_NORMAL, false,
+										   &buffer);
+	if (action == BLK_NEEDS_REDO)
+	{
+		Page		page = (Page) BufferGetPage(buffer);
+		OffsetNumber *nowunused;
+		Size		datalen;
+		OffsetNumber *offnum;
+
+		nowunused = (OffsetNumber *) XLogRecGetBlockData(record, 0, &datalen);
+
+		/* Shouldn't be a record unless there's something to do */
+		Assert(xlrec->nunused > 0);
+
+		/* Update all now-unused line pointers */
+		offnum = nowunused;
+		for (int i = 0; i < xlrec->nunused; i++)
+		{
+			OffsetNumber off = *offnum++;
+			ItemId		lp = PageGetItemId(page, off);
+
+			Assert(ItemIdIsDead(lp) && !ItemIdHasStorage(lp));
+			ItemIdSetUnused(lp);
+		}
+
+		/* Attempt to truncate line pointer array now */
+		PageTruncateLinePointerArray(page);
+
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(buffer);
+	}
+
+	if (BufferIsValid(buffer))
+	{
+		Size		freespace = PageGetHeapFreeSpace(BufferGetPage(buffer));
+		RelFileNode rnode;
+
+		XLogRecGetBlockTag(record, 0, &rnode, NULL, &blkno);
+
+		UnlockReleaseBuffer(buffer);
+
+		/*
+		 * After vacuuming LP_DEAD items from a page, it's useful to update
+		 * the FSM about it, as it may cause the page become target for
+		 * insertions later even if vacuum decides not to visit it (which is
+		 * possible if gets marked all-visible.)
+		 *
+		 * Do this regardless of a full-page image being applied, since the
+		 * FSM data is not in the page anyway.
+		 */
+		XLogRecordPageWithFreeSpace(rnode, blkno, freespace);
+	}
+}
+
+/*
+ * Replay XLOG_HEAP2_VISIBLE record.
+ *
+ * The critical integrity requirement here is that we must never end up with
+ * a situation where the visibility map bit is set, and the page-level
+ * PD_ALL_VISIBLE bit is clear.  If that were to occur, then a subsequent
+ * page modification would fail to clear the visibility map bit.
+ */
+static void
+heap_xlog_visible(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_visible *xlrec = (xl_heap_visible *) XLogRecGetData(record);
+	Buffer		vmbuffer = InvalidBuffer;
+	Buffer		buffer;
+	Page		page;
+	RelFileNode rnode;
+	BlockNumber blkno;
+	XLogRedoAction action;
+
+	XLogRecGetBlockTag(record, 1, &rnode, NULL, &blkno);
+
+	/*
+	 * If there are any Hot Standby transactions running that have an xmin
+	 * horizon old enough that this page isn't all-visible for them, they
+	 * might incorrectly decide that an index-only scan can skip a heap fetch.
+	 *
+	 * NB: It might be better to throw some kind of "soft" conflict here that
+	 * forces any index-only scan that is in flight to perform heap fetches,
+	 * rather than killing the transaction outright.
+	 */
+	if (InHotStandby)
+		ResolveRecoveryConflictWithSnapshot(xlrec->cutoff_xid, rnode);
+
+	/*
+	 * Read the heap page, if it still exists. If the heap file has dropped or
+	 * truncated later in recovery, we don't need to update the page, but we'd
+	 * better still update the visibility map.
+	 */
+	action = XLogReadBufferForRedo(record, 1, &buffer);
+	if (action == BLK_NEEDS_REDO)
+	{
+		/*
+		 * We don't bump the LSN of the heap page when setting the visibility
+		 * map bit (unless checksums or wal_hint_bits is enabled, in which
+		 * case we must). This exposes us to torn page hazards, but since
+		 * we're not inspecting the existing page contents in any way, we
+		 * don't care.
+		 *
+		 * However, all operations that clear the visibility map bit *do* bump
+		 * the LSN, and those operations will only be replayed if the XLOG LSN
+		 * follows the page LSN.  Thus, if the page LSN has advanced past our
+		 * XLOG record's LSN, we mustn't mark the page all-visible, because
+		 * the subsequent update won't be replayed to clear the flag.
+		 */
+		page = BufferGetPage(buffer);
+
+		PageSetAllVisible(page);
+
+		if (XLogHintBitIsNeeded())
+			PageSetLSN(page, lsn);
+
+		MarkBufferDirty(buffer);
+	}
+	else if (action == BLK_RESTORED)
+	{
+		/*
+		 * If heap block was backed up, we already restored it and there's
+		 * nothing more to do. (This can only happen with checksums or
+		 * wal_log_hints enabled.)
+		 */
+	}
+
+	if (BufferIsValid(buffer))
+	{
+		Size		space = PageGetFreeSpace(BufferGetPage(buffer));
+
+		UnlockReleaseBuffer(buffer);
+
+		/*
+		 * Since FSM is not WAL-logged and only updated heuristically, it
+		 * easily becomes stale in standbys.  If the standby is later promoted
+		 * and runs VACUUM, it will skip updating individual free space
+		 * figures for pages that became all-visible (or all-frozen, depending
+		 * on the vacuum mode,) which is troublesome when FreeSpaceMapVacuum
+		 * propagates too optimistic free space values to upper FSM layers;
+		 * later inserters try to use such pages only to find out that they
+		 * are unusable.  This can cause long stalls when there are many such
+		 * pages.
+		 *
+		 * Forestall those problems by updating FSM's idea about a page that
+		 * is becoming all-visible or all-frozen.
+		 *
+		 * Do this regardless of a full-page image being applied, since the
+		 * FSM data is not in the page anyway.
+		 */
+		if (xlrec->flags & VISIBILITYMAP_VALID_BITS)
+			XLogRecordPageWithFreeSpace(rnode, blkno, space);
+	}
+
+	/*
+	 * Even if we skipped the heap page update due to the LSN interlock, it's
+	 * still safe to update the visibility map.  Any WAL record that clears
+	 * the visibility map bit does so before checking the page LSN, so any
+	 * bits that need to be cleared will still be cleared.
+	 */
+	if (XLogReadBufferForRedoExtended(record, 0, RBM_ZERO_ON_ERROR, false,
+									  &vmbuffer) == BLK_NEEDS_REDO)
+	{
+		Page		vmpage = BufferGetPage(vmbuffer);
+		Relation	reln;
+
+		/* initialize the page if it was read as zeros */
+		if (PageIsNew(vmpage))
+			PageInit(vmpage, BLCKSZ, 0);
+
+		/*
+		 * XLogReadBufferForRedoExtended locked the buffer. But
+		 * visibilitymap_set will handle locking itself.
+		 */
+		LockBuffer(vmbuffer, BUFFER_LOCK_UNLOCK);
+
+		reln = CreateFakeRelcacheEntry(rnode);
+		visibilitymap_pin(reln, blkno, &vmbuffer);
+
+		/*
+		 * Don't set the bit if replay has already passed this point.
+		 *
+		 * It might be safe to do this unconditionally; if replay has passed
+		 * this point, we'll replay at least as far this time as we did
+		 * before, and if this bit needs to be cleared, the record responsible
+		 * for doing so should be again replayed, and clear it.  For right
+		 * now, out of an abundance of conservatism, we use the same test here
+		 * we did for the heap page.  If this results in a dropped bit, no
+		 * real harm is done; and the next VACUUM will fix it.
+		 */
+		if (lsn > PageGetLSN(vmpage))
+			visibilitymap_set(reln, blkno, InvalidBuffer, lsn, vmbuffer,
+							  xlrec->cutoff_xid, xlrec->flags);
+
+		ReleaseBuffer(vmbuffer);
+		FreeFakeRelcacheEntry(reln);
+	}
+	else if (BufferIsValid(vmbuffer))
+		UnlockReleaseBuffer(vmbuffer);
+}
+
+/*
+ * Replay XLOG_HEAP2_FREEZE_PAGE records
+ */
+static void
+heap_xlog_freeze_page(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_freeze_page *xlrec = (xl_heap_freeze_page *) XLogRecGetData(record);
+	TransactionId cutoff_xid = xlrec->cutoff_xid;
+	Buffer		buffer;
+	int			ntup;
+
+	/*
+	 * In Hot Standby mode, ensure that there's no queries running which still
+	 * consider the frozen xids as running.
+	 */
+	if (InHotStandby)
+	{
+		RelFileNode rnode;
+		TransactionId latestRemovedXid = cutoff_xid;
+
+		TransactionIdRetreat(latestRemovedXid);
+
+		XLogRecGetBlockTag(record, 0, &rnode, NULL, NULL);
+		ResolveRecoveryConflictWithSnapshot(latestRemovedXid, rnode);
+	}
+
+	if (XLogReadBufferForRedo(record, 0, &buffer) == BLK_NEEDS_REDO)
+	{
+		Page		page = BufferGetPage(buffer);
+		xl_heap_freeze_tuple *tuples;
+
+		tuples = (xl_heap_freeze_tuple *) XLogRecGetBlockData(record, 0, NULL);
+
+		/* now execute freeze plan for each frozen tuple */
+		for (ntup = 0; ntup < xlrec->ntuples; ntup++)
+		{
+			xl_heap_freeze_tuple *xlrec_tp;
+			ItemId		lp;
+			HeapTupleHeader tuple;
+
+			xlrec_tp = &tuples[ntup];
+			lp = PageGetItemId(page, xlrec_tp->offset); /* offsets are one-based */
+			tuple = (HeapTupleHeader) PageGetItem(page, lp);
+
+			heap_execute_freeze_tuple(tuple, xlrec_tp);
+		}
+
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(buffer);
+	}
+	if (BufferIsValid(buffer))
+		UnlockReleaseBuffer(buffer);
+}
+
+/*
+ * Given an "infobits" field from an XLog record, set the correct bits in the
+ * given infomask and infomask2 for the tuple touched by the record.
+ *
+ * (This is the reverse of compute_infobits).
+ */
+static void
+fix_infomask_from_infobits(uint8 infobits, uint16 *infomask, uint16 *infomask2)
+{
+	*infomask &= ~(HEAP_XMAX_IS_MULTI | HEAP_XMAX_LOCK_ONLY |
+				   HEAP_XMAX_KEYSHR_LOCK | HEAP_XMAX_EXCL_LOCK);
+	*infomask2 &= ~HEAP_KEYS_UPDATED;
+
+	if (infobits & XLHL_XMAX_IS_MULTI)
+		*infomask |= HEAP_XMAX_IS_MULTI;
+	if (infobits & XLHL_XMAX_LOCK_ONLY)
+		*infomask |= HEAP_XMAX_LOCK_ONLY;
+	if (infobits & XLHL_XMAX_EXCL_LOCK)
+		*infomask |= HEAP_XMAX_EXCL_LOCK;
+	/* note HEAP_XMAX_SHR_LOCK isn't considered here */
+	if (infobits & XLHL_XMAX_KEYSHR_LOCK)
+		*infomask |= HEAP_XMAX_KEYSHR_LOCK;
+
+	if (infobits & XLHL_KEYS_UPDATED)
+		*infomask2 |= HEAP_KEYS_UPDATED;
+}
+
+static void
+heap_xlog_delete(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_delete *xlrec = (xl_heap_delete *) XLogRecGetData(record);
+	Buffer		buffer;
+	Page		page;
+	ItemId		lp = NULL;
+	HeapTupleHeader htup;
+	BlockNumber blkno;
+	RelFileNode target_node;
+	ItemPointerData target_tid;
+
+	XLogRecGetBlockTag(record, 0, &target_node, NULL, &blkno);
+	ItemPointerSetBlockNumber(&target_tid, blkno);
+	ItemPointerSetOffsetNumber(&target_tid, xlrec->offnum);
+
+	/*
+	 * The visibility map may need to be fixed even if the heap page is
+	 * already up-to-date.
+	 */
+	if (xlrec->flags & XLH_DELETE_ALL_VISIBLE_CLEARED)
+	{
+		Relation	reln = CreateFakeRelcacheEntry(target_node);
+		Buffer		vmbuffer = InvalidBuffer;
+
+		visibilitymap_pin(reln, blkno, &vmbuffer);
+		visibilitymap_clear(reln, blkno, vmbuffer, VISIBILITYMAP_VALID_BITS);
+		ReleaseBuffer(vmbuffer);
+		FreeFakeRelcacheEntry(reln);
+	}
+
+	if (XLogReadBufferForRedo(record, 0, &buffer) == BLK_NEEDS_REDO)
+	{
+		page = BufferGetPage(buffer);
+
+		if (PageGetMaxOffsetNumber(page) >= xlrec->offnum)
+			lp = PageGetItemId(page, xlrec->offnum);
+
+		if (PageGetMaxOffsetNumber(page) < xlrec->offnum || !ItemIdIsNormal(lp))
+			elog(PANIC, "invalid lp");
+
+		htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+		htup->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED);
+		htup->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+		HeapTupleHeaderClearHotUpdated(htup);
+		fix_infomask_from_infobits(xlrec->infobits_set,
+								   &htup->t_infomask, &htup->t_infomask2);
+		if (!(xlrec->flags & XLH_DELETE_IS_SUPER))
+			HeapTupleHeaderSetXmax(htup, xlrec->xmax);
+		else
+			HeapTupleHeaderSetXmin(htup, InvalidTransactionId);
+		HeapTupleHeaderSetCmax(htup, FirstCommandId, false);
+
+		/* Mark the page as a candidate for pruning */
+		PageSetPrunable(page, XLogRecGetXid(record));
+
+		if (xlrec->flags & XLH_DELETE_ALL_VISIBLE_CLEARED)
+			PageClearAllVisible(page);
+
+		/* Make sure t_ctid is set correctly */
+		if (xlrec->flags & XLH_DELETE_IS_PARTITION_MOVE)
+			HeapTupleHeaderSetMovedPartitions(htup);
+		else
+			htup->t_ctid = target_tid;
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(buffer);
+	}
+	if (BufferIsValid(buffer))
+		UnlockReleaseBuffer(buffer);
+}
+
+static void
+heap_xlog_insert(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_insert *xlrec = (xl_heap_insert *) XLogRecGetData(record);
+	Buffer		buffer;
+	Page		page;
+	union
+	{
+		HeapTupleHeaderData hdr;
+		char		data[MaxHeapTupleSize];
+	}			tbuf;
+	HeapTupleHeader htup;
+	xl_heap_header xlhdr;
+	uint32		newlen;
+	Size		freespace = 0;
+	RelFileNode target_node;
+	BlockNumber blkno;
+	ItemPointerData target_tid;
+	XLogRedoAction action;
+
+	XLogRecGetBlockTag(record, 0, &target_node, NULL, &blkno);
+	ItemPointerSetBlockNumber(&target_tid, blkno);
+	ItemPointerSetOffsetNumber(&target_tid, xlrec->offnum);
+
+	/*
+	 * The visibility map may need to be fixed even if the heap page is
+	 * already up-to-date.
+	 */
+	if (xlrec->flags & XLH_INSERT_ALL_VISIBLE_CLEARED)
+	{
+		Relation	reln = CreateFakeRelcacheEntry(target_node);
+		Buffer		vmbuffer = InvalidBuffer;
+
+		visibilitymap_pin(reln, blkno, &vmbuffer);
+		visibilitymap_clear(reln, blkno, vmbuffer, VISIBILITYMAP_VALID_BITS);
+		ReleaseBuffer(vmbuffer);
+		FreeFakeRelcacheEntry(reln);
+	}
+
+	/*
+	 * If we inserted the first and only tuple on the page, re-initialize the
+	 * page from scratch.
+	 */
+	if (XLogRecGetInfo(record) & XLOG_HEAP_INIT_PAGE)
+	{
+		buffer = XLogInitBufferForRedo(record, 0);
+		page = BufferGetPage(buffer);
+		PageInit(page, BufferGetPageSize(buffer), 0);
+		action = BLK_NEEDS_REDO;
+	}
+	else
+		action = XLogReadBufferForRedo(record, 0, &buffer);
+	if (action == BLK_NEEDS_REDO)
+	{
+		Size		datalen;
+		char	   *data;
+
+		page = BufferGetPage(buffer);
+
+		if (PageGetMaxOffsetNumber(page) + 1 < xlrec->offnum)
+			elog(PANIC, "invalid max offset number");
+
+		data = XLogRecGetBlockData(record, 0, &datalen);
+
+		newlen = datalen - SizeOfHeapHeader;
+		Assert(datalen > SizeOfHeapHeader && newlen <= MaxHeapTupleSize);
+		memcpy((char *) &xlhdr, data, SizeOfHeapHeader);
+		data += SizeOfHeapHeader;
+
+		htup = &tbuf.hdr;
+		MemSet((char *) htup, 0, SizeofHeapTupleHeader);
+		/* PG73FORMAT: get bitmap [+ padding] [+ oid] + data */
+		memcpy((char *) htup + SizeofHeapTupleHeader,
+			   data,
+			   newlen);
+		newlen += SizeofHeapTupleHeader;
+		htup->t_infomask2 = xlhdr.t_infomask2;
+		htup->t_infomask = xlhdr.t_infomask;
+		htup->t_hoff = xlhdr.t_hoff;
+		HeapTupleHeaderSetXmin(htup, XLogRecGetXid(record));
+		HeapTupleHeaderSetCmin(htup, FirstCommandId);
+		htup->t_ctid = target_tid;
+
+		if (PageAddItem(page, (Item) htup, newlen, xlrec->offnum,
+						true, true) == InvalidOffsetNumber)
+			elog(PANIC, "failed to add tuple");
+
+		freespace = PageGetHeapFreeSpace(page); /* needed to update FSM below */
+
+		PageSetLSN(page, lsn);
+
+		if (xlrec->flags & XLH_INSERT_ALL_VISIBLE_CLEARED)
+			PageClearAllVisible(page);
+
+		/* XLH_INSERT_ALL_FROZEN_SET implies that all tuples are visible */
+		if (xlrec->flags & XLH_INSERT_ALL_FROZEN_SET)
+			PageSetAllVisible(page);
+
+		MarkBufferDirty(buffer);
+	}
+	if (BufferIsValid(buffer))
+		UnlockReleaseBuffer(buffer);
+
+	/*
+	 * If the page is running low on free space, update the FSM as well.
+	 * Arbitrarily, our definition of "low" is less than 20%. We can't do much
+	 * better than that without knowing the fill-factor for the table.
+	 *
+	 * XXX: Don't do this if the page was restored from full page image. We
+	 * don't bother to update the FSM in that case, it doesn't need to be
+	 * totally accurate anyway.
+	 */
+	if (action == BLK_NEEDS_REDO && freespace < BLCKSZ / 5)
+		XLogRecordPageWithFreeSpace(target_node, blkno, freespace);
+}
+
+/*
+ * Handles MULTI_INSERT record type.
+ */
+static void
+heap_xlog_multi_insert(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_multi_insert *xlrec;
+	RelFileNode rnode;
+	BlockNumber blkno;
+	Buffer		buffer;
+	Page		page;
+	union
+	{
+		HeapTupleHeaderData hdr;
+		char		data[MaxHeapTupleSize];
+	}			tbuf;
+	HeapTupleHeader htup;
+	uint32		newlen;
+	Size		freespace = 0;
+	int			i;
+	bool		isinit = (XLogRecGetInfo(record) & XLOG_HEAP_INIT_PAGE) != 0;
+	XLogRedoAction action;
+
+	/*
+	 * Insertion doesn't overwrite MVCC data, so no conflict processing is
+	 * required.
+	 */
+	xlrec = (xl_heap_multi_insert *) XLogRecGetData(record);
+
+	XLogRecGetBlockTag(record, 0, &rnode, NULL, &blkno);
+
+	/* check that the mutually exclusive flags are not both set */
+	Assert(!((xlrec->flags & XLH_INSERT_ALL_VISIBLE_CLEARED) &&
+			 (xlrec->flags & XLH_INSERT_ALL_FROZEN_SET)));
+
+	/*
+	 * The visibility map may need to be fixed even if the heap page is
+	 * already up-to-date.
+	 */
+	if (xlrec->flags & XLH_INSERT_ALL_VISIBLE_CLEARED)
+	{
+		Relation	reln = CreateFakeRelcacheEntry(rnode);
+		Buffer		vmbuffer = InvalidBuffer;
+
+		visibilitymap_pin(reln, blkno, &vmbuffer);
+		visibilitymap_clear(reln, blkno, vmbuffer, VISIBILITYMAP_VALID_BITS);
+		ReleaseBuffer(vmbuffer);
+		FreeFakeRelcacheEntry(reln);
+	}
+
+	if (isinit)
+	{
+		buffer = XLogInitBufferForRedo(record, 0);
+		page = BufferGetPage(buffer);
+		PageInit(page, BufferGetPageSize(buffer), 0);
+		action = BLK_NEEDS_REDO;
+	}
+	else
+		action = XLogReadBufferForRedo(record, 0, &buffer);
+	if (action == BLK_NEEDS_REDO)
+	{
+		char	   *tupdata;
+		char	   *endptr;
+		Size		len;
+
+		/* Tuples are stored as block data */
+		tupdata = XLogRecGetBlockData(record, 0, &len);
+		endptr = tupdata + len;
+
+		page = (Page) BufferGetPage(buffer);
+
+		for (i = 0; i < xlrec->ntuples; i++)
+		{
+			OffsetNumber offnum;
+			xl_multi_insert_tuple *xlhdr;
+
+			/*
+			 * If we're reinitializing the page, the tuples are stored in
+			 * order from FirstOffsetNumber. Otherwise there's an array of
+			 * offsets in the WAL record, and the tuples come after that.
+			 */
+			if (isinit)
+				offnum = FirstOffsetNumber + i;
+			else
+				offnum = xlrec->offsets[i];
+			if (PageGetMaxOffsetNumber(page) + 1 < offnum)
+				elog(PANIC, "invalid max offset number");
+
+			xlhdr = (xl_multi_insert_tuple *) SHORTALIGN(tupdata);
+			tupdata = ((char *) xlhdr) + SizeOfMultiInsertTuple;
+
+			newlen = xlhdr->datalen;
+			Assert(newlen <= MaxHeapTupleSize);
+			htup = &tbuf.hdr;
+			MemSet((char *) htup, 0, SizeofHeapTupleHeader);
+			/* PG73FORMAT: get bitmap [+ padding] [+ oid] + data */
+			memcpy((char *) htup + SizeofHeapTupleHeader,
+				   (char *) tupdata,
+				   newlen);
+			tupdata += newlen;
+
+			newlen += SizeofHeapTupleHeader;
+			htup->t_infomask2 = xlhdr->t_infomask2;
+			htup->t_infomask = xlhdr->t_infomask;
+			htup->t_hoff = xlhdr->t_hoff;
+			HeapTupleHeaderSetXmin(htup, XLogRecGetXid(record));
+			HeapTupleHeaderSetCmin(htup, FirstCommandId);
+			ItemPointerSetBlockNumber(&htup->t_ctid, blkno);
+			ItemPointerSetOffsetNumber(&htup->t_ctid, offnum);
+
+			offnum = PageAddItem(page, (Item) htup, newlen, offnum, true, true);
+			if (offnum == InvalidOffsetNumber)
+				elog(PANIC, "failed to add tuple");
+		}
+		if (tupdata != endptr)
+			elog(PANIC, "total tuple length mismatch");
+
+		freespace = PageGetHeapFreeSpace(page); /* needed to update FSM below */
+
+		PageSetLSN(page, lsn);
+
+		if (xlrec->flags & XLH_INSERT_ALL_VISIBLE_CLEARED)
+			PageClearAllVisible(page);
+
+		/* XLH_INSERT_ALL_FROZEN_SET implies that all tuples are visible */
+		if (xlrec->flags & XLH_INSERT_ALL_FROZEN_SET)
+			PageSetAllVisible(page);
+
+		MarkBufferDirty(buffer);
+	}
+	if (BufferIsValid(buffer))
+		UnlockReleaseBuffer(buffer);
+
+	/*
+	 * If the page is running low on free space, update the FSM as well.
+	 * Arbitrarily, our definition of "low" is less than 20%. We can't do much
+	 * better than that without knowing the fill-factor for the table.
+	 *
+	 * XXX: Don't do this if the page was restored from full page image. We
+	 * don't bother to update the FSM in that case, it doesn't need to be
+	 * totally accurate anyway.
+	 */
+	if (action == BLK_NEEDS_REDO && freespace < BLCKSZ / 5)
+		XLogRecordPageWithFreeSpace(rnode, blkno, freespace);
+}
+
+/*
+ * Handles UPDATE and HOT_UPDATE
+ */
+static void
+heap_xlog_update(XLogReaderState *record, bool hot_update)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_update *xlrec = (xl_heap_update *) XLogRecGetData(record);
+	RelFileNode rnode;
+	BlockNumber oldblk;
+	BlockNumber newblk;
+	ItemPointerData newtid;
+	Buffer		obuffer,
+				nbuffer;
+	Page		page;
+	OffsetNumber offnum;
+	ItemId		lp = NULL;
+	HeapTupleData oldtup;
+	HeapTupleHeader htup;
+	uint16		prefixlen = 0,
+				suffixlen = 0;
+	char	   *newp;
+	union
+	{
+		HeapTupleHeaderData hdr;
+		char		data[MaxHeapTupleSize];
+	}			tbuf;
+	xl_heap_header xlhdr;
+	uint32		newlen;
+	Size		freespace = 0;
+	XLogRedoAction oldaction;
+	XLogRedoAction newaction;
+
+	/* initialize to keep the compiler quiet */
+	oldtup.t_data = NULL;
+	oldtup.t_len = 0;
+
+	XLogRecGetBlockTag(record, 0, &rnode, NULL, &newblk);
+	if (XLogRecGetBlockTagExtended(record, 1, NULL, NULL, &oldblk, NULL))
+	{
+		/* HOT updates are never done across pages */
+		Assert(!hot_update);
+	}
+	else
+		oldblk = newblk;
+
+	ItemPointerSet(&newtid, newblk, xlrec->new_offnum);
+
+	/*
+	 * The visibility map may need to be fixed even if the heap page is
+	 * already up-to-date.
+	 */
+	if (xlrec->flags & XLH_UPDATE_OLD_ALL_VISIBLE_CLEARED)
+	{
+		Relation	reln = CreateFakeRelcacheEntry(rnode);
+		Buffer		vmbuffer = InvalidBuffer;
+
+		visibilitymap_pin(reln, oldblk, &vmbuffer);
+		visibilitymap_clear(reln, oldblk, vmbuffer, VISIBILITYMAP_VALID_BITS);
+		ReleaseBuffer(vmbuffer);
+		FreeFakeRelcacheEntry(reln);
+	}
+
+	/*
+	 * In normal operation, it is important to lock the two pages in
+	 * page-number order, to avoid possible deadlocks against other update
+	 * operations going the other way.  However, during WAL replay there can
+	 * be no other update happening, so we don't need to worry about that. But
+	 * we *do* need to worry that we don't expose an inconsistent state to Hot
+	 * Standby queries --- so the original page can't be unlocked before we've
+	 * added the new tuple to the new page.
+	 */
+
+	/* Deal with old tuple version */
+	oldaction = XLogReadBufferForRedo(record, (oldblk == newblk) ? 0 : 1,
+									  &obuffer);
+	if (oldaction == BLK_NEEDS_REDO)
+	{
+		page = BufferGetPage(obuffer);
+		offnum = xlrec->old_offnum;
+		if (PageGetMaxOffsetNumber(page) >= offnum)
+			lp = PageGetItemId(page, offnum);
+
+		if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp))
+			elog(PANIC, "invalid lp");
+
+		htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+		oldtup.t_data = htup;
+		oldtup.t_len = ItemIdGetLength(lp);
+
+		htup->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED);
+		htup->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+		if (hot_update)
+			HeapTupleHeaderSetHotUpdated(htup);
+		else
+			HeapTupleHeaderClearHotUpdated(htup);
+		fix_infomask_from_infobits(xlrec->old_infobits_set, &htup->t_infomask,
+								   &htup->t_infomask2);
+		HeapTupleHeaderSetXmax(htup, xlrec->old_xmax);
+		HeapTupleHeaderSetCmax(htup, FirstCommandId, false);
+		/* Set forward chain link in t_ctid */
+		htup->t_ctid = newtid;
+
+		/* Mark the page as a candidate for pruning */
+		PageSetPrunable(page, XLogRecGetXid(record));
+
+		if (xlrec->flags & XLH_UPDATE_OLD_ALL_VISIBLE_CLEARED)
+			PageClearAllVisible(page);
+
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(obuffer);
+	}
+
+	/*
+	 * Read the page the new tuple goes into, if different from old.
+	 */
+	if (oldblk == newblk)
+	{
+		nbuffer = obuffer;
+		newaction = oldaction;
+	}
+	else if (XLogRecGetInfo(record) & XLOG_HEAP_INIT_PAGE)
+	{
+		nbuffer = XLogInitBufferForRedo(record, 0);
+		page = (Page) BufferGetPage(nbuffer);
+		PageInit(page, BufferGetPageSize(nbuffer), 0);
+		newaction = BLK_NEEDS_REDO;
+	}
+	else
+		newaction = XLogReadBufferForRedo(record, 0, &nbuffer);
+
+	/*
+	 * The visibility map may need to be fixed even if the heap page is
+	 * already up-to-date.
+	 */
+	if (xlrec->flags & XLH_UPDATE_NEW_ALL_VISIBLE_CLEARED)
+	{
+		Relation	reln = CreateFakeRelcacheEntry(rnode);
+		Buffer		vmbuffer = InvalidBuffer;
+
+		visibilitymap_pin(reln, newblk, &vmbuffer);
+		visibilitymap_clear(reln, newblk, vmbuffer, VISIBILITYMAP_VALID_BITS);
+		ReleaseBuffer(vmbuffer);
+		FreeFakeRelcacheEntry(reln);
+	}
+
+	/* Deal with new tuple */
+	if (newaction == BLK_NEEDS_REDO)
+	{
+		char	   *recdata;
+		char	   *recdata_end;
+		Size		datalen;
+		Size		tuplen;
+
+		recdata = XLogRecGetBlockData(record, 0, &datalen);
+		recdata_end = recdata + datalen;
+
+		page = BufferGetPage(nbuffer);
+
+		offnum = xlrec->new_offnum;
+		if (PageGetMaxOffsetNumber(page) + 1 < offnum)
+			elog(PANIC, "invalid max offset number");
+
+		if (xlrec->flags & XLH_UPDATE_PREFIX_FROM_OLD)
+		{
+			Assert(newblk == oldblk);
+			memcpy(&prefixlen, recdata, sizeof(uint16));
+			recdata += sizeof(uint16);
+		}
+		if (xlrec->flags & XLH_UPDATE_SUFFIX_FROM_OLD)
+		{
+			Assert(newblk == oldblk);
+			memcpy(&suffixlen, recdata, sizeof(uint16));
+			recdata += sizeof(uint16);
+		}
+
+		memcpy((char *) &xlhdr, recdata, SizeOfHeapHeader);
+		recdata += SizeOfHeapHeader;
+
+		tuplen = recdata_end - recdata;
+		Assert(tuplen <= MaxHeapTupleSize);
+
+		htup = &tbuf.hdr;
+		MemSet((char *) htup, 0, SizeofHeapTupleHeader);
+
+		/*
+		 * Reconstruct the new tuple using the prefix and/or suffix from the
+		 * old tuple, and the data stored in the WAL record.
+		 */
+		newp = (char *) htup + SizeofHeapTupleHeader;
+		if (prefixlen > 0)
+		{
+			int			len;
+
+			/* copy bitmap [+ padding] [+ oid] from WAL record */
+			len = xlhdr.t_hoff - SizeofHeapTupleHeader;
+			memcpy(newp, recdata, len);
+			recdata += len;
+			newp += len;
+
+			/* copy prefix from old tuple */
+			memcpy(newp, (char *) oldtup.t_data + oldtup.t_data->t_hoff, prefixlen);
+			newp += prefixlen;
+
+			/* copy new tuple data from WAL record */
+			len = tuplen - (xlhdr.t_hoff - SizeofHeapTupleHeader);
+			memcpy(newp, recdata, len);
+			recdata += len;
+			newp += len;
+		}
+		else
+		{
+			/*
+			 * copy bitmap [+ padding] [+ oid] + data from record, all in one
+			 * go
+			 */
+			memcpy(newp, recdata, tuplen);
+			recdata += tuplen;
+			newp += tuplen;
+		}
+		Assert(recdata == recdata_end);
+
+		/* copy suffix from old tuple */
+		if (suffixlen > 0)
+			memcpy(newp, (char *) oldtup.t_data + oldtup.t_len - suffixlen, suffixlen);
+
+		newlen = SizeofHeapTupleHeader + tuplen + prefixlen + suffixlen;
+		htup->t_infomask2 = xlhdr.t_infomask2;
+		htup->t_infomask = xlhdr.t_infomask;
+		htup->t_hoff = xlhdr.t_hoff;
+
+		HeapTupleHeaderSetXmin(htup, XLogRecGetXid(record));
+		HeapTupleHeaderSetCmin(htup, FirstCommandId);
+		HeapTupleHeaderSetXmax(htup, xlrec->new_xmax);
+		/* Make sure there is no forward chain link in t_ctid */
+		htup->t_ctid = newtid;
+
+		offnum = PageAddItem(page, (Item) htup, newlen, offnum, true, true);
+		if (offnum == InvalidOffsetNumber)
+			elog(PANIC, "failed to add tuple");
+
+		if (xlrec->flags & XLH_UPDATE_NEW_ALL_VISIBLE_CLEARED)
+			PageClearAllVisible(page);
+
+		freespace = PageGetHeapFreeSpace(page); /* needed to update FSM below */
+
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(nbuffer);
+	}
+
+	if (BufferIsValid(nbuffer) && nbuffer != obuffer)
+		UnlockReleaseBuffer(nbuffer);
+	if (BufferIsValid(obuffer))
+		UnlockReleaseBuffer(obuffer);
+
+	/*
+	 * If the new page is running low on free space, update the FSM as well.
+	 * Arbitrarily, our definition of "low" is less than 20%. We can't do much
+	 * better than that without knowing the fill-factor for the table.
+	 *
+	 * However, don't update the FSM on HOT updates, because after crash
+	 * recovery, either the old or the new tuple will certainly be dead and
+	 * prunable. After pruning, the page will have roughly as much free space
+	 * as it did before the update, assuming the new tuple is about the same
+	 * size as the old one.
+	 *
+	 * XXX: Don't do this if the page was restored from full page image. We
+	 * don't bother to update the FSM in that case, it doesn't need to be
+	 * totally accurate anyway.
+	 */
+	if (newaction == BLK_NEEDS_REDO && !hot_update && freespace < BLCKSZ / 5)
+		XLogRecordPageWithFreeSpace(rnode, newblk, freespace);
+}
+
+static void
+heap_xlog_confirm(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_confirm *xlrec = (xl_heap_confirm *) XLogRecGetData(record);
+	Buffer		buffer;
+	Page		page;
+	OffsetNumber offnum;
+	ItemId		lp = NULL;
+	HeapTupleHeader htup;
+
+	if (XLogReadBufferForRedo(record, 0, &buffer) == BLK_NEEDS_REDO)
+	{
+		page = BufferGetPage(buffer);
+
+		offnum = xlrec->offnum;
+		if (PageGetMaxOffsetNumber(page) >= offnum)
+			lp = PageGetItemId(page, offnum);
+
+		if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp))
+			elog(PANIC, "invalid lp");
+
+		htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+		/*
+		 * Confirm tuple as actually inserted
+		 */
+		ItemPointerSet(&htup->t_ctid, BufferGetBlockNumber(buffer), offnum);
+
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(buffer);
+	}
+	if (BufferIsValid(buffer))
+		UnlockReleaseBuffer(buffer);
+}
+
+static void
+heap_xlog_lock(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_lock *xlrec = (xl_heap_lock *) XLogRecGetData(record);
+	Buffer		buffer;
+	Page		page;
+	OffsetNumber offnum;
+	ItemId		lp = NULL;
+	HeapTupleHeader htup;
+
+	/*
+	 * The visibility map may need to be fixed even if the heap page is
+	 * already up-to-date.
+	 */
+	if (xlrec->flags & XLH_LOCK_ALL_FROZEN_CLEARED)
+	{
+		RelFileNode rnode;
+		Buffer		vmbuffer = InvalidBuffer;
+		BlockNumber block;
+		Relation	reln;
+
+		XLogRecGetBlockTag(record, 0, &rnode, NULL, &block);
+		reln = CreateFakeRelcacheEntry(rnode);
+
+		visibilitymap_pin(reln, block, &vmbuffer);
+		visibilitymap_clear(reln, block, vmbuffer, VISIBILITYMAP_ALL_FROZEN);
+
+		ReleaseBuffer(vmbuffer);
+		FreeFakeRelcacheEntry(reln);
+	}
+
+	if (XLogReadBufferForRedo(record, 0, &buffer) == BLK_NEEDS_REDO)
+	{
+		page = (Page) BufferGetPage(buffer);
+
+		offnum = xlrec->offnum;
+		if (PageGetMaxOffsetNumber(page) >= offnum)
+			lp = PageGetItemId(page, offnum);
+
+		if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp))
+			elog(PANIC, "invalid lp");
+
+		htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+		htup->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED);
+		htup->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+		fix_infomask_from_infobits(xlrec->infobits_set, &htup->t_infomask,
+								   &htup->t_infomask2);
+
+		/*
+		 * Clear relevant update flags, but only if the modified infomask says
+		 * there's no update.
+		 */
+		if (HEAP_XMAX_IS_LOCKED_ONLY(htup->t_infomask))
+		{
+			HeapTupleHeaderClearHotUpdated(htup);
+			/* Make sure there is no forward chain link in t_ctid */
+			ItemPointerSet(&htup->t_ctid,
+						   BufferGetBlockNumber(buffer),
+						   offnum);
+		}
+		HeapTupleHeaderSetXmax(htup, xlrec->locking_xid);
+		HeapTupleHeaderSetCmax(htup, FirstCommandId, false);
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(buffer);
+	}
+	if (BufferIsValid(buffer))
+		UnlockReleaseBuffer(buffer);
+}
+
+static void
+heap_xlog_lock_updated(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_lock_updated *xlrec;
+	Buffer		buffer;
+	Page		page;
+	OffsetNumber offnum;
+	ItemId		lp = NULL;
+	HeapTupleHeader htup;
+
+	xlrec = (xl_heap_lock_updated *) XLogRecGetData(record);
+
+	/*
+	 * The visibility map may need to be fixed even if the heap page is
+	 * already up-to-date.
+	 */
+	if (xlrec->flags & XLH_LOCK_ALL_FROZEN_CLEARED)
+	{
+		RelFileNode rnode;
+		Buffer		vmbuffer = InvalidBuffer;
+		BlockNumber block;
+		Relation	reln;
+
+		XLogRecGetBlockTag(record, 0, &rnode, NULL, &block);
+		reln = CreateFakeRelcacheEntry(rnode);
+
+		visibilitymap_pin(reln, block, &vmbuffer);
+		visibilitymap_clear(reln, block, vmbuffer, VISIBILITYMAP_ALL_FROZEN);
+
+		ReleaseBuffer(vmbuffer);
+		FreeFakeRelcacheEntry(reln);
+	}
+
+	if (XLogReadBufferForRedo(record, 0, &buffer) == BLK_NEEDS_REDO)
+	{
+		page = BufferGetPage(buffer);
+
+		offnum = xlrec->offnum;
+		if (PageGetMaxOffsetNumber(page) >= offnum)
+			lp = PageGetItemId(page, offnum);
+
+		if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp))
+			elog(PANIC, "invalid lp");
+
+		htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+		htup->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED);
+		htup->t_infomask2 &= ~HEAP_KEYS_UPDATED;
+		fix_infomask_from_infobits(xlrec->infobits_set, &htup->t_infomask,
+								   &htup->t_infomask2);
+		HeapTupleHeaderSetXmax(htup, xlrec->xmax);
+
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(buffer);
+	}
+	if (BufferIsValid(buffer))
+		UnlockReleaseBuffer(buffer);
+}
+
+static void
+heap_xlog_inplace(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	xl_heap_inplace *xlrec = (xl_heap_inplace *) XLogRecGetData(record);
+	Buffer		buffer;
+	Page		page;
+	OffsetNumber offnum;
+	ItemId		lp = NULL;
+	HeapTupleHeader htup;
+	uint32		oldlen;
+	Size		newlen;
+
+	if (XLogReadBufferForRedo(record, 0, &buffer) == BLK_NEEDS_REDO)
+	{
+		char	   *newtup = XLogRecGetBlockData(record, 0, &newlen);
+
+		page = BufferGetPage(buffer);
+
+		offnum = xlrec->offnum;
+		if (PageGetMaxOffsetNumber(page) >= offnum)
+			lp = PageGetItemId(page, offnum);
+
+		if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp))
+			elog(PANIC, "invalid lp");
+
+		htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+		oldlen = ItemIdGetLength(lp) - htup->t_hoff;
+		if (oldlen != newlen)
+			elog(PANIC, "wrong tuple length");
+
+		memcpy((char *) htup + htup->t_hoff, newtup, newlen);
+
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(buffer);
+	}
+	if (BufferIsValid(buffer))
+		UnlockReleaseBuffer(buffer);
+}
+
+void
+heap_redo(XLogReaderState *record)
+{
+	uint8		info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
+
+	/*
+	 * These operations don't overwrite MVCC data so no conflict processing is
+	 * required. The ones in heap2 rmgr do.
+	 */
+
+	switch (info & XLOG_HEAP_OPMASK)
+	{
+		case XLOG_HEAP_INSERT:
+			heap_xlog_insert(record);
+			break;
+		case XLOG_HEAP_DELETE:
+			heap_xlog_delete(record);
+			break;
+		case XLOG_HEAP_UPDATE:
+			heap_xlog_update(record, false);
+			break;
+		case XLOG_HEAP_TRUNCATE:
+
+			/*
+			 * TRUNCATE is a no-op because the actions are already logged as
+			 * SMGR WAL records.  TRUNCATE WAL record only exists for logical
+			 * decoding.
+			 */
+			break;
+		case XLOG_HEAP_HOT_UPDATE:
+			heap_xlog_update(record, true);
+			break;
+		case XLOG_HEAP_CONFIRM:
+			heap_xlog_confirm(record);
+			break;
+		case XLOG_HEAP_LOCK:
+			heap_xlog_lock(record);
+			break;
+		case XLOG_HEAP_INPLACE:
+			heap_xlog_inplace(record);
+			break;
+		default:
+			elog(PANIC, "heap_redo: unknown op code %u", info);
+	}
+}
+
+void
+heap2_redo(XLogReaderState *record)
+{
+	uint8		info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
+
+	switch (info & XLOG_HEAP_OPMASK)
+	{
+		case XLOG_HEAP2_PRUNE:
+			heap_xlog_prune(record);
+			break;
+		case XLOG_HEAP2_VACUUM:
+			heap_xlog_vacuum(record);
+			break;
+		case XLOG_HEAP2_FREEZE_PAGE:
+			heap_xlog_freeze_page(record);
+			break;
+		case XLOG_HEAP2_VISIBLE:
+			heap_xlog_visible(record);
+			break;
+		case XLOG_HEAP2_MULTI_INSERT:
+			heap_xlog_multi_insert(record);
+			break;
+		case XLOG_HEAP2_LOCK_UPDATED:
+			heap_xlog_lock_updated(record);
+			break;
+		case XLOG_HEAP2_NEW_CID:
+
+			/*
+			 * Nothing to do on a real replay, only used during logical
+			 * decoding.
+			 */
+			break;
+		case XLOG_HEAP2_REWRITE:
+			heap_xlog_logical_rewrite(record);
+			break;
+		default:
+			elog(PANIC, "heap2_redo: unknown op code %u", info);
+	}
+}
+
+/*
+ * Mask a heap page before performing consistency checks on it.
+ */
+void
+heap_mask(char *pagedata, BlockNumber blkno)
+{
+	Page		page = (Page) pagedata;
+	OffsetNumber off;
+
+	mask_page_lsn_and_checksum(page);
+
+	mask_page_hint_bits(page);
+	mask_unused_space(page);
+
+	for (off = 1; off <= PageGetMaxOffsetNumber(page); off++)
+	{
+		ItemId		iid = PageGetItemId(page, off);
+		char	   *page_item;
+
+		page_item = (char *) (page + ItemIdGetOffset(iid));
+
+		if (ItemIdIsNormal(iid))
+		{
+			HeapTupleHeader page_htup = (HeapTupleHeader) page_item;
+
+			/*
+			 * If xmin of a tuple is not yet frozen, we should ignore
+			 * differences in hint bits, since they can be set without
+			 * emitting WAL.
+			 */
+			if (!HeapTupleHeaderXminFrozen(page_htup))
+				page_htup->t_infomask &= ~HEAP_XACT_MASK;
+			else
+			{
+				/* Still we need to mask xmax hint bits. */
+				page_htup->t_infomask &= ~HEAP_XMAX_INVALID;
+				page_htup->t_infomask &= ~HEAP_XMAX_COMMITTED;
+			}
+
+			/*
+			 * During replay, we set Command Id to FirstCommandId. Hence, mask
+			 * it. See heap_xlog_insert() for details.
+			 */
+			page_htup->t_choice.t_heap.t_field3.t_cid = MASK_MARKER;
+
+			/*
+			 * For a speculative tuple, heap_insert() does not set ctid in the
+			 * caller-passed heap tuple itself, leaving the ctid field to
+			 * contain a speculative token value - a per-backend monotonically
+			 * increasing identifier. Besides, it does not WAL-log ctid under
+			 * any circumstances.
+			 *
+			 * During redo, heap_xlog_insert() sets t_ctid to current block
+			 * number and self offset number. It doesn't care about any
+			 * speculative insertions on the primary. Hence, we set t_ctid to
+			 * current block number and self offset number to ignore any
+			 * inconsistency.
+			 */
+			if (HeapTupleHeaderIsSpeculative(page_htup))
+				ItemPointerSet(&page_htup->t_ctid, blkno, off);
+
+			/*
+			 * NB: Not ignoring ctid changes due to the tuple having moved
+			 * (i.e. HeapTupleHeaderIndicatesMovedPartitions), because that's
+			 * important information that needs to be in-sync between primary
+			 * and standby, and thus is WAL logged.
+			 */
+		}
+
+		/*
+		 * Ignore any padding bytes after the tuple, when the length of the
+		 * item is not MAXALIGNed.
+		 */
+		if (ItemIdHasStorage(iid))
+		{
+			int			len = ItemIdGetLength(iid);
+			int			padlen = MAXALIGN(len) - len;
+
+			if (padlen > 0)
+				memset(page_item + len, MASK_MARKER, padlen);
+		}
+	}
+}
+
+/*
+ * HeapCheckForSerializableConflictOut
+ *		We are reading a tuple.  If it's not visible, there may be a
+ *		rw-conflict out with the inserter.  Otherwise, if it is visible to us
+ *		but has been deleted, there may be a rw-conflict out with the deleter.
+ *
+ * We will determine the top level xid of the writing transaction with which
+ * we may be in conflict, and ask CheckForSerializableConflictOut() to check
+ * for overlap with our own transaction.
+ *
+ * This function should be called just about anywhere in heapam.c where a
+ * tuple has been read. The caller must hold at least a shared lock on the
+ * buffer, because this function might set hint bits on the tuple. There is
+ * currently no known reason to call this function from an index AM.
+ */
+void
+HeapCheckForSerializableConflictOut(bool visible, Relation relation,
+									HeapTuple tuple, Buffer buffer,
+									Snapshot snapshot)
+{
+	TransactionId xid;
+	HTSV_Result htsvResult;
+
+	if (!CheckForSerializableConflictOutNeeded(relation, snapshot))
+		return;
+
+	/*
+	 * Check to see whether the tuple has been written to by a concurrent
+	 * transaction, either to create it not visible to us, or to delete it
+	 * while it is visible to us.  The "visible" bool indicates whether the
+	 * tuple is visible to us, while HeapTupleSatisfiesVacuum checks what else
+	 * is going on with it.
+	 *
+	 * In the event of a concurrently inserted tuple that also happens to have
+	 * been concurrently updated (by a separate transaction), the xmin of the
+	 * tuple will be used -- not the updater's xid.
+	 */
+	htsvResult = HeapTupleSatisfiesVacuum(tuple, TransactionXmin, buffer);
+	switch (htsvResult)
+	{
+		case HEAPTUPLE_LIVE:
+			if (visible)
+				return;
+			xid = HeapTupleHeaderGetXmin(tuple->t_data);
+			break;
+		case HEAPTUPLE_RECENTLY_DEAD:
+		case HEAPTUPLE_DELETE_IN_PROGRESS:
+			if (visible)
+				xid = HeapTupleHeaderGetUpdateXid(tuple->t_data);
+			else
+				xid = HeapTupleHeaderGetXmin(tuple->t_data);
+
+			if (TransactionIdPrecedes(xid, TransactionXmin))
+			{
+				/* This is like the HEAPTUPLE_DEAD case */
+				Assert(!visible);
+				return;
+			}
+			break;
+		case HEAPTUPLE_INSERT_IN_PROGRESS:
+			xid = HeapTupleHeaderGetXmin(tuple->t_data);
+			break;
+		case HEAPTUPLE_DEAD:
+			Assert(!visible);
+			return;
+		default:
+
+			/*
+			 * The only way to get to this default clause is if a new value is
+			 * added to the enum type without adding it to this switch
+			 * statement.  That's a bug, so elog.
+			 */
+			elog(ERROR, "unrecognized return value from HeapTupleSatisfiesVacuum: %u", htsvResult);
+
+			/*
+			 * In spite of having all enum values covered and calling elog on
+			 * this default, some compilers think this is a code path which
+			 * allows xid to be used below without initialization. Silence
+			 * that warning.
+			 */
+			xid = InvalidTransactionId;
+	}
+
+	Assert(TransactionIdIsValid(xid));
+	Assert(TransactionIdFollowsOrEquals(xid, TransactionXmin));
+
+	/*
+	 * Find top level xid.  Bail out if xid is too early to be a conflict, or
+	 * if it's our own xid.
+	 */
+	if (TransactionIdEquals(xid, GetTopTransactionIdIfAny()))
+		return;
+	xid = SubTransGetTopmostTransaction(xid);
+	if (TransactionIdPrecedes(xid, TransactionXmin))
+		return;
+
+	CheckForSerializableConflictOut(relation, xid, snapshot);
+}