Compressing the AFTER TRIGGER queue

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
new file mode 100644
index 4c31f19..4799dc2
*** a/src/backend/commands/trigger.c
--- b/src/backend/commands/trigger.c
*************** typedef SetConstraintStateData *SetConst
*** 2851,2864 ****
  /*
   * Per-trigger-event data
   *
!  * The actual per-event data, AfterTriggerEventData, includes DONE/IN_PROGRESS
!  * status bits and one or two tuple CTIDs.	Each event record also has an
!  * associated AfterTriggerSharedData that is shared across all instances
!  * of similar events within a "chunk".
!  *
!  * We arrange not to waste storage on ate_ctid2 for non-update events.
!  * We could go further and not store either ctid for statement-level triggers,
!  * but that seems unlikely to be worth the trouble.
   *
   * Note: ats_firing_id is initially zero and is set to something else when
   * AFTER_TRIGGER_IN_PROGRESS is set.  It indicates which trigger firing
--- 2851,2864 ----
  /*
   * Per-trigger-event data
   *
!  * The actual per-event data includes DONE/IN_PROGRESS status bits, an
!  * encoded CTID and a reference to an associated AfterTriggerSharedData that
!  * is shared across all instances of similar events within a "chunk".  The
!  * encoding uses between 1 and 9 bytes per event, and is optimised so that
!  * the smallest amount of space is used for the types of event that are most
!  * likely to occur often - events where the CTID is the same or close to the
!  * last event's CTID.  This happens when there are multiple triggers on a
!  * table, or the table is traversed using a sequential or bitmap heap scan.
   *
   * Note: ats_firing_id is initially zero and is set to something else when
   * AFTER_TRIGGER_IN_PROGRESS is set.  It indicates which trigger firing
*************** typedef SetConstraintStateData *SetConst
*** 2869,2881 ****
   * cycles.	So we need only ensure that ats_firing_id is zero when attaching
   * a new event to an existing AfterTriggerSharedData record.
   */
- typedef uint32 TriggerFlags;
  
! #define AFTER_TRIGGER_OFFSET			0x0FFFFFFF		/* must be low-order
! 														 * bits */
! #define AFTER_TRIGGER_2CTIDS			0x10000000
! #define AFTER_TRIGGER_DONE				0x20000000
! #define AFTER_TRIGGER_IN_PROGRESS		0x40000000
  
  typedef struct AfterTriggerSharedData *AfterTriggerShared;
  
--- 2869,2900 ----
   * cycles.	So we need only ensure that ats_firing_id is zero when attaching
   * a new event to an existing AfterTriggerSharedData record.
   */
  
! /*
!  * The first (and possibly the only) byte of an event record contains flags
!  * that determine how the rest of the record is encoded.
!  *
!  * AFTER_TRIGGER_SHARED_DATA_FLAGS (3 bits) determines how the index to the
!  * AfterTriggerSharedData is encoded:
!  *		0-5 => Index of AfterTriggerSharedData (counting back from the end of
!  *			   the chunk).  If the CTID is the same as the previous event,
!  *			   this index is treated as relative to the last event's index.
!  *		6 => Index is encoded in 1 additional byte.
!  *		7 => Index is encoded in 2 additional bytes.
!  *
!  * AFTER_TRIGGER_CTID_FLAGS (3 bits) determines how the CTID is encoded:
!  *		0 => CTID is same as previous event.
!  *		1-6 => Difference between this event's CTID and previous CTID encoded
!  *			   using 1-6 bytes.
!  *		7 => CTID is offset by 1 relative to previous event.
!  *
!  * The flag byte is then followed by 0-2 bytes for the index to the shared
!  * data and 0-6 bytes for the CTID.
!  */
! #define AFTER_TRIGGER_DONE				0x80
! #define AFTER_TRIGGER_IN_PROGRESS		0x40
! #define AFTER_TRIGGER_SHARED_DATA_FLAGS	0x38
! #define AFTER_TRIGGER_CTID_FLAGS		0x07
  
  typedef struct AfterTriggerSharedData *AfterTriggerShared;
  
*************** typedef struct AfterTriggerEventData *Af
*** 2891,2914 ****
  
  typedef struct AfterTriggerEventData
  {
! 	TriggerFlags ate_flags;		/* status bits and offset to shared data */
! 	ItemPointerData ate_ctid1;	/* inserted, deleted, or old updated tuple */
! 	ItemPointerData ate_ctid2;	/* new updated tuple */
  } AfterTriggerEventData;
  
! /* This struct must exactly match the one above except for not having ctid2 */
! typedef struct AfterTriggerEventDataOneCtid
! {
! 	TriggerFlags ate_flags;		/* status bits and offset to shared data */
! 	ItemPointerData ate_ctid1;	/* inserted, deleted, or old updated tuple */
! }	AfterTriggerEventDataOneCtid;
  
! #define SizeofTriggerEvent(evt) \
! 	(((evt)->ate_flags & AFTER_TRIGGER_2CTIDS) ? \
! 	 sizeof(AfterTriggerEventData) : sizeof(AfterTriggerEventDataOneCtid))
  
! #define GetTriggerSharedData(evt) \
! 	((AfterTriggerShared) ((char *) (evt) + ((evt)->ate_flags & AFTER_TRIGGER_OFFSET)))
  
  /*
   * To avoid palloc overhead, we keep trigger events in arrays in successively-
--- 2910,2932 ----
  
  typedef struct AfterTriggerEventData
  {
! 	char	ate_flags;		/* flag byte */
! 	char	ate_data[8];	/* variable length array (0-8 bytes) */
  } AfterTriggerEventData;
  
! /* Macros to help extract the AfterTriggerSharedData index from an event */
! #define SharedDataFlags(evt) \
! 	(((evt)->ate_flags & AFTER_TRIGGER_SHARED_DATA_FLAGS) >> 3)
! #define SizeofSharedDataIndex(evt) \
! 	(SharedDataFlags(evt) < 6 ? 0 : (SharedDataFlags(evt) - 5))
  
! /* Macros to help extract the CTID from an event */
! #define CtidFlags(evt)	((evt)->ate_flags & AFTER_TRIGGER_CTID_FLAGS)
! #define SizeofCtid(evt)	(CtidFlags(evt) == 7 ? 0 : CtidFlags(evt))
  
! /* Size of an encoded event (1-9 bytes) */
! #define SizeofTriggerEvent(evt) \
! 	(1 + SizeofSharedDataIndex(evt) + SizeofCtid(evt))
  
  /*
   * To avoid palloc overhead, we keep trigger events in arrays in successively-
*************** typedef struct AfterTriggerEventList
*** 2934,2939 ****
--- 2952,2959 ----
  	AfterTriggerEventChunk *head;
  	AfterTriggerEventChunk *tail;
  	char	   *tailfree;		/* freeptr of tail chunk */
+ 	uint16		last_ats_idx;	/* Shared data index of last event */
+ 	ItemPointerData last_ctid;	/* CTID of last event */
  } AfterTriggerEventList;
  
  /* Macros to help in iterating over a list of events */
*************** typedef struct AfterTriggerEventList
*** 2947,2952 ****
--- 2967,2975 ----
  #define for_each_event_chunk(eptr, cptr, evtlist) \
  	for_each_chunk(cptr, evtlist) for_each_event(eptr, cptr)
  
+ #define AfterTriggerSharedDataIdx(chunk, evtsharedptr) \
+ 	((uint16) (((AfterTriggerShared) (chunk)->endptr) - evtsharedptr) - 1)
+ 
  
  /*
   * All per-transaction data for the AFTER TRIGGERS module.
*************** typedef AfterTriggersData *AfterTriggers
*** 3024,3034 ****
  static AfterTriggers afterTriggers;
  
  
! static void AfterTriggerExecute(AfterTriggerEvent event,
! 					Relation rel, TriggerDesc *trigdesc,
! 					FmgrInfo *finfo,
! 					Instrumentation *instr,
! 					MemoryContext per_tuple_context);
  static SetConstraintState SetConstraintStateCreate(int numalloc);
  static SetConstraintState SetConstraintStateCopy(SetConstraintState state);
  static SetConstraintState SetConstraintStateAddItem(SetConstraintState state,
--- 3047,3056 ----
  static AfterTriggers afterTriggers;
  
  
! static void AfterTriggerExecute(Relation rel, TriggerDesc *trigdesc,
! 					FmgrInfo *finfo, Instrumentation *instr,
! 					MemoryContext per_tuple_context,
! 					TriggerEvent event, Oid tgoid, ItemPointer ctid);
  static SetConstraintState SetConstraintStateCreate(int numalloc);
  static SetConstraintState SetConstraintStateCopy(SetConstraintState state);
  static SetConstraintState SetConstraintStateAddItem(SetConstraintState state,
*************** static SetConstraintState SetConstraintS
*** 3036,3041 ****
--- 3058,3304 ----
  
  
  /* ----------
+  * encodeAfterTriggerEvent()
+  *
+  *	Encode a trigger event for storage in the AfterTriggerEventList.  This
+  *	aims to store the most common events using a single byte, but may take
+  *	up to 9 bytes in some cases.
+  *
+  *	Returns the number of bytes used to encode the event.
+  * ----------
+  */
+ static inline int
+ encodeAfterTriggerEvent(AfterTriggerEvent evt,
+ 						bool row_trigger,
+ 						uint16 ats_idx,
+ 						ItemPointer ctid,
+ 						uint16 prev_ats_idx,
+ 						ItemPointer prev_ctid)
+ {
+ 	bool	store_ctid = row_trigger && !ItemPointerEquals(ctid, prev_ctid);
+ 	int		ate_data_idx = 0;
+ 	char	ats_flags;
+ 	char	ctid_flags;
+ 
+ 	/*
+ 	 * Work out how to store the shared data index compactly.  Try to code for
+ 	 * the most common cases first, and have them use the minimum space.
+ 	 *
+ 	 * If the CTID isn't changing, then a common case is that the shared data
+ 	 * index is increasing by a small amount (next trigger on the same row).
+ 	 * If this 'small amount' is less than 6 it will fit in the flag byte.
+ 	 * In most cases it will be a different trigger, so we can offset by 1,
+ 	 * under the assumption that the index will not be the same.
+ 	 */
+ 	if (!store_ctid && ats_idx > prev_ats_idx && ats_idx < prev_ats_idx + 7)
+ 		ats_flags = (char) (ats_idx - prev_ats_idx - 1); /* 0-5 */
+ 
+ 	/*
+ 	 * Else if the CTID is changing, the shared data index will often reset
+ 	 * back to a small value.  If this is less than 6 it will fit in the flag
+ 	 * byte.
+ 	 */
+ 	else if (store_ctid && ats_idx < 6)
+ 		ats_flags = (char) ats_idx; /* 0-5 */
+ 
+ 	/*
+ 	 * Else indexes less than 256 require one additional byte.  The chunk
+ 	 * size adapts so that typically not too many shared records are used
+ 	 * per chunk (typically less than 200) but we can't rely on that.
+ 	 */
+ 	else if (ats_idx < 256)
+ 	{
+ 		ats_flags = 6;
+ 		evt->ate_data[ate_data_idx++] = (char) ats_idx;
+ 	}
+ 
+ 	/*
+ 	 * Otherwise indexes larger than 255 require 2 additional bytes.
+ 	 */
+ 	else
+ 	{
+ 		ats_flags = 7;
+ 		evt->ate_data[ate_data_idx++] = (char) (ats_idx >> 8);
+ 		evt->ate_data[ate_data_idx++] = (char) (ats_idx & 0xFF);
+ 	}
+ 
+ 	if (store_ctid)
+ 	{
+ 		/*
+ 		 * Store the CTID compactly.  In this block we know that the CTID has
+ 		 * changed, but hopefully only by a small amount.
+ 		 *
+ 		 * First test for the common case where it has increased by one.  We
+ 		 * simplify the encoding and decoding by discounting the case of it
+ 		 * crossing into the next block (can that ever really happen?).
+ 		 */
+ 		BlockNumber blk1 = ItemPointerGetBlockNumber(prev_ctid);
+ 		BlockNumber blk2 = ItemPointerGetBlockNumber(ctid);
+ 		OffsetNumber off1 = ItemPointerGetOffsetNumber(prev_ctid);
+ 		OffsetNumber off2 = ItemPointerGetOffsetNumber(ctid);
+ 
+ 		if (blk2 == blk1 && off2 == off1 + 1)
+ 		{
+ 			ctid_flags = 7;
+ 		}
+ 		else
+ 		{
+ 			/*
+ 			 * XOR the 2 CTIDs together and store the result (MSB first)
+ 			 * discarding any leading zero bytes.  This reduces the space
+ 			 * needed for nearby CTIDs, for which the high bytes will be
+ 			 * equal and XOR to zero.
+ 			 */
+ 			BlockNumber blk_xor = blk1 ^ blk2;
+ 			OffsetNumber off_xor = off1 ^ off2;
+ 
+ 			/* Number of bytes needed for the encoded CTID (1-6) */
+ 			ctid_flags = blk_xor == 0 ? ((off_xor & 0xFF00) != 0 ? 2 : 1) :
+ 						 (blk_xor & 0xFF000000) != 0 ? 6 :
+ 						 (blk_xor & 0xFF0000) != 0 ? 5 :
+ 						 (blk_xor & 0xFF00) != 0 ? 4 : 3;
+ 
+ 			switch (ctid_flags)
+ 			{
+ 				case 6:
+ 					evt->ate_data[ate_data_idx++] = (char) (blk_xor >> 24);
+ 					/* fall through to next case */
+ 				case 5:
+ 					evt->ate_data[ate_data_idx++] = (char) (blk_xor >> 16);
+ 					/* fall through to next case */
+ 				case 4:
+ 					evt->ate_data[ate_data_idx++] = (char) (blk_xor >> 8);
+ 					/* fall through to next case */
+ 				case 3:
+ 					evt->ate_data[ate_data_idx++] = (char) blk_xor;
+ 					/* fall through to next case */
+ 				case 2:
+ 					evt->ate_data[ate_data_idx++] = (char) (off_xor >> 8);
+ 					/* fall through to next case */
+ 				case 1:
+ 					evt->ate_data[ate_data_idx++] = (char) off_xor;
+ 					break;
+ 				default:
+ 					/* can't happen */
+ 					break;
+ 			}
+ 		}
+ 	}
+ 	else
+ 		ctid_flags = 0; /* No CTID needed */
+ 
+ 	evt->ate_flags = (ats_flags << 3) | ctid_flags;
+ 
+ 	return ate_data_idx + 1; /* Total size of encoded event */
+ }
+ 
+ /* ----------
+  * GetTriggerSharedData()
+  *
+  *	Returns a pointer to a trigger event's shared data.
+  * ----------
+  */
+ static inline AfterTriggerShared
+ GetTriggerSharedData(AfterTriggerEvent evt, AfterTriggerEventChunk *chunk,
+ 					 uint16 prev_ats_idx)
+ {
+ 	int shared_data_flags = SharedDataFlags(evt);
+ 	uint16 ats_idx;
+ 
+ 	if (shared_data_flags < 6)
+ 	{
+ 		if (CtidFlags(evt) == 0)
+ 			/* Next trigger on same row, uses a relative index */
+ 			ats_idx = prev_ats_idx + (uint16) shared_data_flags + 1;
+ 		else
+ 			/* First trigger on a new row, with index < 6 */
+ 			ats_idx = (uint16) shared_data_flags;
+ 	}
+ 	else if (shared_data_flags == 6)
+ 	{
+ 		/* 1-byte shared data index follows flag byte */
+ 		ats_idx = (uint16) evt->ate_data[0];
+ 	}
+ 	else /* shared_data_flags == 7 */
+ 	{
+ 		/* 2-byte shared data index follow flag byte */
+ 		ats_idx = (((uint16) evt->ate_data[0]) << 8) | evt->ate_data[1];
+ 	}
+ 	return ((AfterTriggerShared) chunk->endptr) - ats_idx - 1;
+ }
+ 
+ /* ----------
+  * GetTriggerCtid()
+  *
+  *	Get the CTID encoded in an AfterTriggerEvent.
+  * ----------
+  */
+ static inline void
+ GetTriggerCtid(AfterTriggerEvent evt, ItemPointer prev_ctid, ItemPointer ctid)
+ {
+ 	if (CtidFlags(evt) == 0)
+ 	{
+ 		/* CTID is same as that of previous event */
+ 		ItemPointerCopy(prev_ctid, ctid);
+ 	}
+ 	else if (CtidFlags(evt) == 7)
+ 	{
+ 		/*
+ 		 * CTID is the previous value plus one.  Note the encoding used
+ 		 * explicitly prevents this carrying over into the next block.
+ 		 */
+ 		ItemPointerSet(ctid, ItemPointerGetBlockNumber(prev_ctid),
+ 					   ItemPointerGetOffsetNumber(prev_ctid) + 1);
+ 	}
+ 	else
+ 	{
+ 		/*
+ 		 * Values in the range 1-6 indicate an encoded difference from the
+ 		 * previous CTID.  This difference is computed by XORing the two CTIDs
+ 		 * and storing the result (MSB first) after discarding any leading
+ 		 * zero bytes.  To reproduce the original CTID, we just XOR the
+ 		 * difference bytes again.
+ 		 */
+ 		unsigned char *ctid_diffs = ((unsigned char *)evt) + 1 +
+ 									SizeofSharedDataIndex(evt);
+ 		BlockNumber blkno = ItemPointerGetBlockNumber(prev_ctid);
+ 		OffsetNumber offno = ItemPointerGetOffsetNumber(prev_ctid);
+ 
+ 		switch (CtidFlags(evt))
+ 		{
+ 			case 6:
+ 				blkno ^= ((BlockNumber) *ctid_diffs) << 24;
+ 				ctid_diffs++;
+ 				/* fall through to next case */
+ 			case 5:
+ 				blkno ^= ((BlockNumber) *ctid_diffs) << 16;
+ 				ctid_diffs++;
+ 				/* fall through to next case */
+ 			case 4:
+ 				blkno ^= ((BlockNumber) *ctid_diffs) << 8;
+ 				ctid_diffs++;
+ 				/* fall through to next case */
+ 			case 3:
+ 				blkno ^= (BlockNumber) *ctid_diffs;
+ 				ctid_diffs++;
+ 				/* fall through to next case */
+ 			case 2:
+ 				offno ^= ((OffsetNumber) *ctid_diffs) << 8;
+ 				ctid_diffs++;
+ 				/* fall through to next case */
+ 			case 1:
+ 				offno ^= (OffsetNumber) *ctid_diffs;
+ 				break;
+ 			default:
+ 				/* can't happen */
+ 				break;
+ 		}
+ 		ItemPointerSet(ctid, blkno, offno);
+ 	}
+ }
+ 
+ 
+ /* ----------
   * afterTriggerCheckState()
   *
   *	Returns true if the trigger event is actually in state DEFERRED.
*************** afterTriggerCheckState(AfterTriggerShare
*** 3085,3102 ****
   * ----------
   */
  static void
! afterTriggerAddEvent(AfterTriggerEventList *events,
! 					 AfterTriggerEvent event, AfterTriggerShared evtshared)
  {
! 	Size		eventsize = SizeofTriggerEvent(event);
  	Size		needed = eventsize + sizeof(AfterTriggerSharedData);
  	AfterTriggerEventChunk *chunk;
  	AfterTriggerShared newshared;
! 	AfterTriggerEvent newevent;
  
  	/*
  	 * If empty list or not enough room in the tail chunk, make a new chunk.
! 	 * We assume here that a new shared record will always be needed.
  	 */
  	chunk = events->tail;
  	if (chunk == NULL ||
--- 3348,3368 ----
   * ----------
   */
  static void
! afterTriggerAddEvent(AfterTriggerEventList *events, ItemPointer ctid,
! 					 AfterTriggerShared evtshared)
  {
! 	bool		row_trigger = (evtshared->ats_event & TRIGGER_EVENT_ROW) != 0;
! 	Size		eventsize = sizeof(AfterTriggerEventData); /* worst case */
  	Size		needed = eventsize + sizeof(AfterTriggerSharedData);
  	AfterTriggerEventChunk *chunk;
  	AfterTriggerShared newshared;
! 	AfterTriggerEventData newevent;
! 	uint16		ats_idx;
  
  	/*
  	 * If empty list or not enough room in the tail chunk, make a new chunk.
! 	 * We assume here a worst case event record size and that a new shared
! 	 * record will always be needed.
  	 */
  	chunk = events->tail;
  	if (chunk == NULL ||
*************** afterTriggerAddEvent(AfterTriggerEventLi
*** 3115,3138 ****
  
  		/*
  		 * Chunk size starts at 1KB and is allowed to increase up to 1MB.
! 		 * These numbers are fairly arbitrary, though there is a hard limit at
! 		 * AFTER_TRIGGER_OFFSET; else we couldn't link event records to their
! 		 * shared records using the available space in ate_flags.  Another
! 		 * constraint is that if the chunk size gets too huge, the search loop
! 		 * below would get slow given a (not too common) usage pattern with
! 		 * many distinct event types in a chunk.  Therefore, we double the
! 		 * preceding chunk size only if there weren't too many shared records
! 		 * in the preceding chunk; otherwise we halve it.  This gives us some
! 		 * ability to adapt to the actual usage pattern of the current query
! 		 * while still having large chunk sizes in typical usage.  All chunk
! 		 * sizes used should be MAXALIGN multiples, to ensure that the shared
! 		 * records will be aligned safely.
  		 */
  #define MIN_CHUNK_SIZE 1024
  #define MAX_CHUNK_SIZE (1024*1024)
  
! #if MAX_CHUNK_SIZE > (AFTER_TRIGGER_OFFSET+1)
! #error MAX_CHUNK_SIZE must not exceed AFTER_TRIGGER_OFFSET
  #endif
  
  		if (chunk == NULL)
--- 3381,3407 ----
  
  		/*
  		 * Chunk size starts at 1KB and is allowed to increase up to 1MB.
! 		 * These numbers are fairly arbitrary, though there is a hard limit
! 		 * set by the fact that we use 16-bit indexes into the shared data
! 		 * records at the end of the chunk.  Another constraint is that if the
! 		 * chunk size gets too huge, the search loop below would get slow
! 		 * given a (not too common) usage pattern with many distinct event
! 		 * types in a chunk.  This would also affect the per-event compression
! 		 * used.  Therefore, we double the preceding chunk size only if there
! 		 * weren't too many shared records in the preceding chunk; otherwise
! 		 * we halve it.  This gives us some ability to adapt to the actual
! 		 * usage pattern of the current query while still having large chunk
! 		 * sizes in typical usage.  All chunk sizes used should be MAXALIGN
! 		 * multiples, to ensure that the shared records will be aligned
! 		 * safely.
  		 */
  #define MIN_CHUNK_SIZE 1024
  #define MAX_CHUNK_SIZE (1024*1024)
+ #define SHARED_DATA_SIZE 16
+ #define MAX_SHARED_DATA_COUNT (256*256)
  
! #if MAX_CHUNK_SIZE > (SHARED_DATA_SIZE * MAX_SHARED_DATA_COUNT)
! #error MAX_CHUNK_SIZE must not exceed SHARED_DATA_SIZE * MAX_SHARED_DATA_COUNT
  #endif
  
  		if (chunk == NULL)
*************** afterTriggerAddEvent(AfterTriggerEventLi
*** 3183,3195 ****
  		newshared->ats_firing_id = 0;	/* just to be sure */
  		chunk->endfree = (char *) newshared;
  	}
  
  	/* Insert the data */
! 	newevent = (AfterTriggerEvent) chunk->freeptr;
! 	memcpy(newevent, event, eventsize);
! 	/* ... and link the new event to its shared record */
! 	newevent->ate_flags &= ~AFTER_TRIGGER_OFFSET;
! 	newevent->ate_flags |= (char *) newshared - (char *) newevent;
  
  	chunk->freeptr += eventsize;
  	events->tailfree = chunk->freeptr;
--- 3452,3467 ----
  		newshared->ats_firing_id = 0;	/* just to be sure */
  		chunk->endfree = (char *) newshared;
  	}
+ 	ats_idx = AfterTriggerSharedDataIdx(chunk, newshared);
  
  	/* Insert the data */
! 	eventsize = encodeAfterTriggerEvent(&newevent, row_trigger, ats_idx,
! 										ctid, events->last_ats_idx,
! 										&events->last_ctid);
! 	memcpy(chunk->freeptr, &newevent, eventsize);
! 	events->last_ats_idx = ats_idx;
! 	if (row_trigger)
! 		ItemPointerCopy(ctid, &events->last_ctid);
  
  	chunk->freeptr += eventsize;
  	events->tailfree = chunk->freeptr;
*************** afterTriggerFreeEventList(AfterTriggerEv
*** 3215,3220 ****
--- 3487,3494 ----
  	events->head = NULL;
  	events->tail = NULL;
  	events->tailfree = NULL;
+ 	events->last_ats_idx = 0;
+ 	ItemPointerSet(&events->last_ctid, 0, 1); /* first valid CTID */
  }
  
  /* ----------
*************** afterTriggerRestoreEventList(AfterTrigge
*** 3268,3290 ****
   *	fmgr lookup cache space at the caller level.  (For triggers fired at
   *	the end of a query, we can even piggyback on the executor's state.)
   *
-  *	event: event currently being fired.
   *	rel: open relation for event.
   *	trigdesc: working copy of rel's trigger info.
   *	finfo: array of fmgr lookup cache entries (one per trigger in trigdesc).
   *	instr: array of EXPLAIN ANALYZE instrumentation nodes (one per trigger),
   *		or NULL if no instrumentation is wanted.
   *	per_tuple_context: memory context to call trigger function in.
   * ----------
   */
  static void
! AfterTriggerExecute(AfterTriggerEvent event,
! 					Relation rel, TriggerDesc *trigdesc,
  					FmgrInfo *finfo, Instrumentation *instr,
! 					MemoryContext per_tuple_context)
  {
! 	AfterTriggerShared evtshared = GetTriggerSharedData(event);
! 	Oid			tgoid = evtshared->ats_tgoid;
  	TriggerData LocTriggerData;
  	HeapTupleData tuple1;
  	HeapTupleData tuple2;
--- 3542,3565 ----
   *	fmgr lookup cache space at the caller level.  (For triggers fired at
   *	the end of a query, we can even piggyback on the executor's state.)
   *
   *	rel: open relation for event.
   *	trigdesc: working copy of rel's trigger info.
   *	finfo: array of fmgr lookup cache entries (one per trigger in trigdesc).
   *	instr: array of EXPLAIN ANALYZE instrumentation nodes (one per trigger),
   *		or NULL if no instrumentation is wanted.
   *	per_tuple_context: memory context to call trigger function in.
+  *	event: type of event being fired.
+  *	tgoid: trigger OID of event being fired.
+  *	ctid: CTID for event (ignored for statement-level events).
   * ----------
   */
  static void
! AfterTriggerExecute(Relation rel, TriggerDesc *trigdesc,
  					FmgrInfo *finfo, Instrumentation *instr,
! 					MemoryContext per_tuple_context,
! 					TriggerEvent event, Oid tgoid, ItemPointer ctid)
  {
! 	ItemPointer new_ctid = NULL;
  	TriggerData LocTriggerData;
  	HeapTupleData tuple1;
  	HeapTupleData tuple2;
*************** AfterTriggerExecute(AfterTriggerEvent ev
*** 3318,3330 ****
  	/*
  	 * Fetch the required tuple(s).
  	 */
! 	if (ItemPointerIsValid(&(event->ate_ctid1)))
  	{
! 		ItemPointerCopy(&(event->ate_ctid1), &(tuple1.t_self));
  		if (!heap_fetch(rel, SnapshotAny, &tuple1, &buffer1, false, NULL))
  			elog(ERROR, "failed to fetch tuple1 for AFTER trigger");
  		LocTriggerData.tg_trigtuple = &tuple1;
  		LocTriggerData.tg_trigtuplebuf = buffer1;
  	}
  	else
  	{
--- 3593,3609 ----
  	/*
  	 * Fetch the required tuple(s).
  	 */
! 	if ((event & TRIGGER_EVENT_ROW) != 0)
  	{
! 		ItemPointerCopy(ctid, &(tuple1.t_self));
  		if (!heap_fetch(rel, SnapshotAny, &tuple1, &buffer1, false, NULL))
  			elog(ERROR, "failed to fetch tuple1 for AFTER trigger");
  		LocTriggerData.tg_trigtuple = &tuple1;
  		LocTriggerData.tg_trigtuplebuf = buffer1;
+ 
+ 		/* for an UPDATE the old tuple points to the new tuple */
+ 		if (TRIGGER_FIRED_BY_UPDATE(event))
+ 			new_ctid = &(tuple1.t_data->t_ctid);
  	}
  	else
  	{
*************** AfterTriggerExecute(AfterTriggerEvent ev
*** 3332,3342 ****
  		LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
  	}
  
! 	/* don't touch ctid2 if not there */
! 	if ((event->ate_flags & AFTER_TRIGGER_2CTIDS) &&
! 		ItemPointerIsValid(&(event->ate_ctid2)))
  	{
! 		ItemPointerCopy(&(event->ate_ctid2), &(tuple2.t_self));
  		if (!heap_fetch(rel, SnapshotAny, &tuple2, &buffer2, false, NULL))
  			elog(ERROR, "failed to fetch tuple2 for AFTER trigger");
  		LocTriggerData.tg_newtuple = &tuple2;
--- 3611,3619 ----
  		LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
  	}
  
! 	if (ItemPointerIsValid(new_ctid))
  	{
! 		ItemPointerCopy(new_ctid, &(tuple2.t_self));
  		if (!heap_fetch(rel, SnapshotAny, &tuple2, &buffer2, false, NULL))
  			elog(ERROR, "failed to fetch tuple2 for AFTER trigger");
  		LocTriggerData.tg_newtuple = &tuple2;
*************** AfterTriggerExecute(AfterTriggerEvent ev
*** 3353,3359 ****
  	 */
  	LocTriggerData.type = T_TriggerData;
  	LocTriggerData.tg_event =
! 		evtshared->ats_event & (TRIGGER_EVENT_OPMASK | TRIGGER_EVENT_ROW);
  	LocTriggerData.tg_relation = rel;
  
  	MemoryContextReset(per_tuple_context);
--- 3630,3636 ----
  	 */
  	LocTriggerData.type = T_TriggerData;
  	LocTriggerData.tg_event =
! 		event & (TRIGGER_EVENT_OPMASK | TRIGGER_EVENT_ROW);
  	LocTriggerData.tg_relation = rel;
  
  	MemoryContextReset(per_tuple_context);
*************** afterTriggerMarkEvents(AfterTriggerEvent
*** 3409,3420 ****
  	bool		found = false;
  	AfterTriggerEvent event;
  	AfterTriggerEventChunk *chunk;
  
  	for_each_event_chunk(event, chunk, *events)
  	{
! 		AfterTriggerShared evtshared = GetTriggerSharedData(event);
  		bool		defer_it = false;
  
  		if (!(event->ate_flags &
  			  (AFTER_TRIGGER_DONE | AFTER_TRIGGER_IN_PROGRESS)))
  		{
--- 3686,3705 ----
  	bool		found = false;
  	AfterTriggerEvent event;
  	AfterTriggerEventChunk *chunk;
+ 	uint16		prev_ats_idx = 0;
+ 	ItemPointerData prev_ctid;
+ 
+ 	ItemPointerSet(&prev_ctid, 0, 1); /* first valid CTID */
  
  	for_each_event_chunk(event, chunk, *events)
  	{
! 		AfterTriggerShared evtshared = GetTriggerSharedData(event, chunk,
! 															prev_ats_idx);
! 		ItemPointerData ctid;
  		bool		defer_it = false;
  
+ 		GetTriggerCtid(event, &prev_ctid, &ctid);
+ 
  		if (!(event->ate_flags &
  			  (AFTER_TRIGGER_DONE | AFTER_TRIGGER_IN_PROGRESS)))
  		{
*************** afterTriggerMarkEvents(AfterTriggerEvent
*** 3443,3452 ****
  		if (defer_it && move_list != NULL)
  		{
  			/* add it to move_list */
! 			afterTriggerAddEvent(move_list, event, evtshared);
  			/* mark original copy "done" so we don't do it again */
  			event->ate_flags |= AFTER_TRIGGER_DONE;
  		}
  	}
  
  	return found;
--- 3728,3740 ----
  		if (defer_it && move_list != NULL)
  		{
  			/* add it to move_list */
! 			afterTriggerAddEvent(move_list, &ctid, evtshared);
  			/* mark original copy "done" so we don't do it again */
  			event->ate_flags |= AFTER_TRIGGER_DONE;
  		}
+ 
+ 		prev_ats_idx = AfterTriggerSharedDataIdx(chunk, evtshared);
+ 		ItemPointerCopy(&ctid, &prev_ctid);
  	}
  
  	return found;
*************** afterTriggerInvokeEvents(AfterTriggerEve
*** 3487,3492 ****
--- 3775,3784 ----
  	TriggerDesc *trigdesc = NULL;
  	FmgrInfo   *finfo = NULL;
  	Instrumentation *instr = NULL;
+ 	uint16		prev_ats_idx = 0;
+ 	ItemPointerData prev_ctid;
+ 
+ 	ItemPointerSet(&prev_ctid, 0, 1); /* first valid CTID */
  
  	/* Make a local EState if need be */
  	if (estate == NULL)
*************** afterTriggerInvokeEvents(AfterTriggerEve
*** 3510,3516 ****
  
  		for_each_event(event, chunk)
  		{
! 			AfterTriggerShared evtshared = GetTriggerSharedData(event);
  
  			/*
  			 * Is it one for me to fire?
--- 3802,3812 ----
  
  		for_each_event(event, chunk)
  		{
! 			AfterTriggerShared evtshared = GetTriggerSharedData(event, chunk,
! 																prev_ats_idx);
! 			ItemPointerData ctid;
! 
! 			GetTriggerCtid(event, &prev_ctid, &ctid);
  
  			/*
  			 * Is it one for me to fire?
*************** afterTriggerInvokeEvents(AfterTriggerEve
*** 3541,3548 ****
  				 * still set, so recursive examinations of the event list
  				 * won't try to re-fire it.
  				 */
! 				AfterTriggerExecute(event, rel, trigdesc, finfo, instr,
! 									per_tuple_context);
  
  				/*
  				 * Mark the event as done.
--- 3837,3845 ----
  				 * still set, so recursive examinations of the event list
  				 * won't try to re-fire it.
  				 */
! 				AfterTriggerExecute(rel, trigdesc, finfo, instr,
! 									per_tuple_context, evtshared->ats_event,
! 									evtshared->ats_tgoid, &ctid);
  
  				/*
  				 * Mark the event as done.
*************** afterTriggerInvokeEvents(AfterTriggerEve
*** 3555,3560 ****
--- 3852,3860 ----
  				/* something remains to be done */
  				all_fired = all_fired_in_chunk = false;
  			}
+ 
+ 			prev_ats_idx = AfterTriggerSharedDataIdx(chunk, evtshared);
+ 			ItemPointerCopy(&ctid, &prev_ctid);
  		}
  
  		/* Clear the chunk if delete_ok and nothing left of interest */
*************** AfterTriggerBeginXact(void)
*** 3620,3625 ****
--- 3920,3927 ----
  	afterTriggers->events.head = NULL;
  	afterTriggers->events.tail = NULL;
  	afterTriggers->events.tailfree = NULL;
+ 	afterTriggers->events.last_ats_idx = 0;
+ 	ItemPointerSet(&afterTriggers->events.last_ctid, 0, 1); /* first valid CTID */
  	afterTriggers->query_depth = -1;
  
  	/* We initialize the query stack to a reasonable size */
*************** AfterTriggerBeginQuery(void)
*** 3679,3684 ****
--- 3981,3988 ----
  	events->head = NULL;
  	events->tail = NULL;
  	events->tailfree = NULL;
+ 	events->last_ats_idx = 0;
+ 	ItemPointerSet(&events->last_ctid, 0, 1); /* first valid CTID */
  }
  
  
*************** AfterTriggerEndSubXact(bool isCommit)
*** 3921,3926 ****
--- 4225,4231 ----
  	AfterTriggerEvent event;
  	AfterTriggerEventChunk *chunk;
  	CommandId	subxact_firing_id;
+ 	uint16		prev_ats_idx = 0;
  
  	/*
  	 * Ignore call if the transaction is in aborted state.	(Probably
*************** AfterTriggerEndSubXact(bool isCommit)
*** 3997,4003 ****
  		subxact_firing_id = afterTriggers->firing_stack[my_level];
  		for_each_event_chunk(event, chunk, afterTriggers->events)
  		{
! 			AfterTriggerShared evtshared = GetTriggerSharedData(event);
  
  			if (event->ate_flags &
  				(AFTER_TRIGGER_DONE | AFTER_TRIGGER_IN_PROGRESS))
--- 4302,4309 ----
  		subxact_firing_id = afterTriggers->firing_stack[my_level];
  		for_each_event_chunk(event, chunk, afterTriggers->events)
  		{
! 			AfterTriggerShared evtshared = GetTriggerSharedData(event, chunk,
! 																prev_ats_idx);
  
  			if (event->ate_flags &
  				(AFTER_TRIGGER_DONE | AFTER_TRIGGER_IN_PROGRESS))
*************** AfterTriggerEndSubXact(bool isCommit)
*** 4006,4011 ****
--- 4312,4318 ----
  					event->ate_flags &=
  						~(AFTER_TRIGGER_DONE | AFTER_TRIGGER_IN_PROGRESS);
  			}
+ 			prev_ats_idx = AfterTriggerSharedDataIdx(chunk, evtshared);
  		}
  	}
  }
*************** AfterTriggerPendingOnRel(Oid relid)
*** 4389,4394 ****
--- 4696,4702 ----
  	AfterTriggerEvent event;
  	AfterTriggerEventChunk *chunk;
  	int			depth;
+ 	uint16		prev_ats_idx = 0;
  
  	/* No-op if we aren't in a transaction.  (Shouldn't happen?) */
  	if (afterTriggers == NULL)
*************** AfterTriggerPendingOnRel(Oid relid)
*** 4397,4403 ****
  	/* Scan queued events */
  	for_each_event_chunk(event, chunk, afterTriggers->events)
  	{
! 		AfterTriggerShared evtshared = GetTriggerSharedData(event);
  
  		/*
  		 * We can ignore completed events.	(Even if a DONE flag is rolled
--- 4705,4712 ----
  	/* Scan queued events */
  	for_each_event_chunk(event, chunk, afterTriggers->events)
  	{
! 		AfterTriggerShared evtshared = GetTriggerSharedData(event, chunk,
! 															prev_ats_idx);
  
  		/*
  		 * We can ignore completed events.	(Even if a DONE flag is rolled
*************** AfterTriggerPendingOnRel(Oid relid)
*** 4409,4414 ****
--- 4718,4725 ----
  
  		if (evtshared->ats_relid == relid)
  			return true;
+ 
+ 		prev_ats_idx = AfterTriggerSharedDataIdx(chunk, evtshared);
  	}
  
  	/*
*************** AfterTriggerPendingOnRel(Oid relid)
*** 4418,4432 ****
  	 */
  	for (depth = 0; depth <= afterTriggers->query_depth; depth++)
  	{
  		for_each_event_chunk(event, chunk, afterTriggers->query_stack[depth])
  		{
! 			AfterTriggerShared evtshared = GetTriggerSharedData(event);
  
  			if (event->ate_flags & AFTER_TRIGGER_DONE)
  				continue;
  
  			if (evtshared->ats_relid == relid)
  				return true;
  		}
  	}
  
--- 4729,4747 ----
  	 */
  	for (depth = 0; depth <= afterTriggers->query_depth; depth++)
  	{
+ 		prev_ats_idx = 0;
  		for_each_event_chunk(event, chunk, afterTriggers->query_stack[depth])
  		{
! 			AfterTriggerShared evtshared = GetTriggerSharedData(event, chunk,
! 																prev_ats_idx);
  
  			if (event->ate_flags & AFTER_TRIGGER_DONE)
  				continue;
  
  			if (evtshared->ats_relid == relid)
  				return true;
+ 
+ 			prev_ats_idx = AfterTriggerSharedDataIdx(chunk, evtshared);
  		}
  	}
  
*************** AfterTriggerSaveEvent(EState *estate, Re
*** 4453,4460 ****
  {
  	Relation	rel = relinfo->ri_RelationDesc;
  	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
- 	AfterTriggerEventData new_event;
  	AfterTriggerSharedData new_shared;
  	int			tgtype_event;
  	int			tgtype_level;
  	int			i;
--- 4768,4775 ----
  {
  	Relation	rel = relinfo->ri_RelationDesc;
  	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
  	AfterTriggerSharedData new_shared;
+ 	ItemPointer	ctid;
  	int			tgtype_event;
  	int			tgtype_level;
  	int			i;
*************** AfterTriggerSaveEvent(EState *estate, Re
*** 4476,4482 ****
  	 * validation is important to make sure we don't walk off the edge of our
  	 * arrays.
  	 */
- 	new_event.ate_flags = 0;
  	switch (event)
  	{
  		case TRIGGER_EVENT_INSERT:
--- 4791,4796 ----
*************** AfterTriggerSaveEvent(EState *estate, Re
*** 4485,4499 ****
  			{
  				Assert(oldtup == NULL);
  				Assert(newtup != NULL);
! 				ItemPointerCopy(&(newtup->t_self), &(new_event.ate_ctid1));
! 				ItemPointerSetInvalid(&(new_event.ate_ctid2));
  			}
  			else
  			{
  				Assert(oldtup == NULL);
  				Assert(newtup == NULL);
! 				ItemPointerSetInvalid(&(new_event.ate_ctid1));
! 				ItemPointerSetInvalid(&(new_event.ate_ctid2));
  			}
  			break;
  		case TRIGGER_EVENT_DELETE:
--- 4799,4811 ----
  			{
  				Assert(oldtup == NULL);
  				Assert(newtup != NULL);
! 				ctid = &newtup->t_self;
  			}
  			else
  			{
  				Assert(oldtup == NULL);
  				Assert(newtup == NULL);
! 				ctid = NULL;
  			}
  			break;
  		case TRIGGER_EVENT_DELETE:
*************** AfterTriggerSaveEvent(EState *estate, Re
*** 4502,4516 ****
  			{
  				Assert(oldtup != NULL);
  				Assert(newtup == NULL);
! 				ItemPointerCopy(&(oldtup->t_self), &(new_event.ate_ctid1));
! 				ItemPointerSetInvalid(&(new_event.ate_ctid2));
  			}
  			else
  			{
  				Assert(oldtup == NULL);
  				Assert(newtup == NULL);
! 				ItemPointerSetInvalid(&(new_event.ate_ctid1));
! 				ItemPointerSetInvalid(&(new_event.ate_ctid2));
  			}
  			break;
  		case TRIGGER_EVENT_UPDATE:
--- 4814,4826 ----
  			{
  				Assert(oldtup != NULL);
  				Assert(newtup == NULL);
! 				ctid = &oldtup->t_self;
  			}
  			else
  			{
  				Assert(oldtup == NULL);
  				Assert(newtup == NULL);
! 				ctid = NULL;
  			}
  			break;
  		case TRIGGER_EVENT_UPDATE:
*************** AfterTriggerSaveEvent(EState *estate, Re
*** 4519,4546 ****
  			{
  				Assert(oldtup != NULL);
  				Assert(newtup != NULL);
! 				ItemPointerCopy(&(oldtup->t_self), &(new_event.ate_ctid1));
! 				ItemPointerCopy(&(newtup->t_self), &(new_event.ate_ctid2));
! 				new_event.ate_flags |= AFTER_TRIGGER_2CTIDS;
  			}
  			else
  			{
  				Assert(oldtup == NULL);
  				Assert(newtup == NULL);
! 				ItemPointerSetInvalid(&(new_event.ate_ctid1));
! 				ItemPointerSetInvalid(&(new_event.ate_ctid2));
  			}
  			break;
  		case TRIGGER_EVENT_TRUNCATE:
  			tgtype_event = TRIGGER_TYPE_TRUNCATE;
  			Assert(oldtup == NULL);
  			Assert(newtup == NULL);
! 			ItemPointerSetInvalid(&(new_event.ate_ctid1));
! 			ItemPointerSetInvalid(&(new_event.ate_ctid2));
  			break;
  		default:
  			elog(ERROR, "invalid after-trigger event code: %d", event);
  			tgtype_event = 0;	/* keep compiler quiet */
  			break;
  	}
  
--- 4829,4853 ----
  			{
  				Assert(oldtup != NULL);
  				Assert(newtup != NULL);
! 				ctid = &oldtup->t_self;
  			}
  			else
  			{
  				Assert(oldtup == NULL);
  				Assert(newtup == NULL);
! 				ctid = NULL;
  			}
  			break;
  		case TRIGGER_EVENT_TRUNCATE:
  			tgtype_event = TRIGGER_TYPE_TRUNCATE;
  			Assert(oldtup == NULL);
  			Assert(newtup == NULL);
! 			ctid = NULL;
  			break;
  		default:
  			elog(ERROR, "invalid after-trigger event code: %d", event);
  			tgtype_event = 0;	/* keep compiler quiet */
+ 			ctid = NULL;
  			break;
  	}
  
*************** AfterTriggerSaveEvent(EState *estate, Re
*** 4627,4632 ****
  		new_shared.ats_firing_id = 0;
  
  		afterTriggerAddEvent(&afterTriggers->query_stack[afterTriggers->query_depth],
! 							 &new_event, &new_shared);
  	}
  }
--- 4934,4939 ----
  		new_shared.ats_firing_id = 0;
  
  		afterTriggerAddEvent(&afterTriggers->query_stack[afterTriggers->query_depth],
! 							 ctid, &new_shared);
  	}
  }