Avoid incrementing the CommandCounter when CommandCounterIncrement is called

but no database changes have been made since the last CommandCounterIncrement.
This should result in a significant improvement in the number of "commands"
that can typically be performed within a transaction before hitting the 2^32
CommandId size limit.  In particular this buys back (and more) the possible
adverse consequences of my previous patch to fix plan caching behavior.

The implementation requires tracking whether the current CommandCounter
value has been "used" to mark any tuples.  CommandCounter values stored into
snapshots are presumed not to be used for this purpose.  This requires some
small executor changes, since the executor used to conflate the curcid of
the snapshot it was using with the command ID to mark output tuples with.
Separating these concepts allows some small simplifications in executor APIs.

Something for the TODO list: look into having CommandCounterIncrement not do
AcceptInvalidationMessages.  It seems fairly bogus to be doing it there,
but exactly where to do it instead isn't clear, and I'm disinclined to mess
with asynchronous behavior during late beta.

1 files changed, 11 insertions, 18 deletions

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 7dc19505342..1b66bd22ba8 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.224 2007/11/16 01:51:22 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.225 2007/11/30 21:22:54 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -51,7 +51,6 @@ static void InsertTrigger(TriggerDesc *trigdesc, Trigger *trigger, int indx);
 static HeapTuple GetTupleForTrigger(EState *estate,
 				   ResultRelInfo *relinfo,
 				   ItemPointer tid,
-				   CommandId cid,
 				   TupleTableSlot **newSlot);
 static HeapTuple ExecCallTriggerFunc(TriggerData *trigdata,
 					int tgindx,
@@ -1801,8 +1800,7 @@ ExecASDeleteTriggers(EState *estate, ResultRelInfo *relinfo)
 
 bool
 ExecBRDeleteTriggers(EState *estate, ResultRelInfo *relinfo,
-					 ItemPointer tupleid,
-					 CommandId cid)
+					 ItemPointer tupleid)
 {
 	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
 	int			ntrigs = trigdesc->n_before_row[TRIGGER_EVENT_DELETE];
@@ -1814,7 +1812,7 @@ ExecBRDeleteTriggers(EState *estate, ResultRelInfo *relinfo,
 	TupleTableSlot *newSlot;
 	int			i;
 
-	trigtuple = GetTupleForTrigger(estate, relinfo, tupleid, cid, &newSlot);
+	trigtuple = GetTupleForTrigger(estate, relinfo, tupleid, &newSlot);
 	if (trigtuple == NULL)
 		return false;
 
@@ -1871,9 +1869,7 @@ ExecARDeleteTriggers(EState *estate, ResultRelInfo *relinfo,
 	if (trigdesc && trigdesc->n_after_row[TRIGGER_EVENT_DELETE] > 0)
 	{
 		HeapTuple	trigtuple = GetTupleForTrigger(estate, relinfo,
-												   tupleid,
-												   (CommandId) 0,
-												   NULL);
+												   tupleid, NULL);
 
 		AfterTriggerSaveEvent(relinfo, TRIGGER_EVENT_DELETE,
 							  true, trigtuple, NULL);
@@ -1952,8 +1948,7 @@ ExecASUpdateTriggers(EState *estate, ResultRelInfo *relinfo)
 
 HeapTuple
 ExecBRUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
-					 ItemPointer tupleid, HeapTuple newtuple,
-					 CommandId cid)
+					 ItemPointer tupleid, HeapTuple newtuple)
 {
 	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
 	int			ntrigs = trigdesc->n_before_row[TRIGGER_EVENT_UPDATE];
@@ -1965,7 +1960,7 @@ ExecBRUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
 	TupleTableSlot *newSlot;
 	int			i;
 
-	trigtuple = GetTupleForTrigger(estate, relinfo, tupleid, cid, &newSlot);
+	trigtuple = GetTupleForTrigger(estate, relinfo, tupleid, &newSlot);
 	if (trigtuple == NULL)
 		return NULL;
 
@@ -2025,9 +2020,7 @@ ExecARUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
 	if (trigdesc && trigdesc->n_after_row[TRIGGER_EVENT_UPDATE] > 0)
 	{
 		HeapTuple	trigtuple = GetTupleForTrigger(estate, relinfo,
-												   tupleid,
-												   (CommandId) 0,
-												   NULL);
+												   tupleid, NULL);
 
 		AfterTriggerSaveEvent(relinfo, TRIGGER_EVENT_UPDATE,
 							  true, trigtuple, newtuple);
@@ -2038,7 +2031,7 @@ ExecARUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
 
 static HeapTuple
 GetTupleForTrigger(EState *estate, ResultRelInfo *relinfo,
-				   ItemPointer tid, CommandId cid,
+				   ItemPointer tid,
 				   TupleTableSlot **newSlot)
 {
 	Relation	relation = relinfo->ri_RelationDesc;
@@ -2060,7 +2053,8 @@ GetTupleForTrigger(EState *estate, ResultRelInfo *relinfo,
 ltrmark:;
 		tuple.t_self = *tid;
 		test = heap_lock_tuple(relation, &tuple, &buffer,
-							   &update_ctid, &update_xmax, cid,
+							   &update_ctid, &update_xmax,
+							   estate->es_output_cid,
 							   LockTupleExclusive, false);
 		switch (test)
 		{
@@ -2086,8 +2080,7 @@ ltrmark:;
 					epqslot = EvalPlanQual(estate,
 										   relinfo->ri_RangeTableIndex,
 										   &update_ctid,
-										   update_xmax,
-										   cid);
+										   update_xmax);
 					if (!TupIsNull(epqslot))
 					{
 						*tid = update_ctid;