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.

4 files changed, 11 insertions, 10 deletions

diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index 8a311dda3ba..9a6fa607a0e 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/xact.h,v 1.91 2007/11/15 21:14:42 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/xact.h,v 1.92 2007/11/30 21:22:54 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -143,7 +143,7 @@ extern TransactionId GetTopTransactionIdIfAny(void);
 extern TransactionId GetCurrentTransactionId(void);
 extern TransactionId GetCurrentTransactionIdIfAny(void);
 extern SubTransactionId GetCurrentSubTransactionId(void);
-extern CommandId GetCurrentCommandId(void);
+extern CommandId GetCurrentCommandId(bool used);
 extern TimestampTz GetCurrentTransactionStartTimestamp(void);
 extern TimestampTz GetCurrentStatementStartTimestamp(void);
 extern TimestampTz GetCurrentTransactionStopTimestamp(void);
diff --git a/src/include/commands/trigger.h b/src/include/commands/trigger.h
index 69ad97b4ec8..5a1d50edf94 100644
--- a/src/include/commands/trigger.h
+++ b/src/include/commands/trigger.h
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/commands/trigger.h,v 1.63 2007/11/15 21:14:43 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/commands/trigger.h,v 1.64 2007/11/30 21:22:54 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -124,8 +124,7 @@ extern void ExecASDeleteTriggers(EState *estate,
 					 ResultRelInfo *relinfo);
 extern bool ExecBRDeleteTriggers(EState *estate,
 					 ResultRelInfo *relinfo,
-					 ItemPointer tupleid,
-					 CommandId cid);
+					 ItemPointer tupleid);
 extern void ExecARDeleteTriggers(EState *estate,
 					 ResultRelInfo *relinfo,
 					 ItemPointer tupleid);
@@ -136,8 +135,7 @@ extern void ExecASUpdateTriggers(EState *estate,
 extern HeapTuple ExecBRUpdateTriggers(EState *estate,
 					 ResultRelInfo *relinfo,
 					 ItemPointer tupleid,
-					 HeapTuple newtuple,
-					 CommandId cid);
+					 HeapTuple newtuple);
 extern void ExecARUpdateTriggers(EState *estate,
 					 ResultRelInfo *relinfo,
 					 ItemPointer tupleid,
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 08b97e3adfc..78a0a2560a3 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/executor/executor.h,v 1.144 2007/11/15 22:25:17 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/executor/executor.h,v 1.145 2007/11/30 21:22:54 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -143,7 +143,7 @@ extern bool ExecContextForcesOids(PlanState *planstate, bool *hasoids);
 extern void ExecConstraints(ResultRelInfo *resultRelInfo,
 				TupleTableSlot *slot, EState *estate);
 extern TupleTableSlot *EvalPlanQual(EState *estate, Index rti,
-			 ItemPointer tid, TransactionId priorXmax, CommandId curCid);
+			 ItemPointer tid, TransactionId priorXmax);
 extern PlanState *ExecGetActivePlanTree(QueryDesc *queryDesc);
 extern DestReceiver *CreateIntoRelDestReceiver(void);
 
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index ca0e9c8fa78..a140a7533d4 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.181 2007/11/15 22:25:17 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.182 2007/11/30 21:22:54 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -311,6 +311,9 @@ typedef struct EState
 	Snapshot	es_crosscheck_snapshot; /* crosscheck time qual for RI */
 	List	   *es_range_table; /* List of RangeTblEntry */
 
+	/* If query can insert/delete tuples, the command ID to mark them with */
+	CommandId	es_output_cid;
+
 	/* Info about target table for insert/update/delete queries: */
 	ResultRelInfo *es_result_relations; /* array of ResultRelInfos */
 	int			es_num_result_relations;		/* length of array */