Add a WHEN clause to CREATE TRIGGER, allowing a boolean expression to be

checked to determine whether the trigger should be fired.

For BEFORE triggers this is mostly a matter of spec compliance; but for AFTER
triggers it can provide a noticeable performance improvement, since queuing of
a deferred trigger event and re-fetching of the row(s) at end of statement can
be short-circuited if the trigger does not need to be fired.

Takahiro Itagaki, reviewed by KaiGai Kohei.

4 files changed, 54 insertions, 22 deletions

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index d7d99bc0aea..60ded334c68 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -26,7 +26,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.334 2009/10/26 02:26:29 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.335 2009/11/20 20:38:10 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -752,6 +752,7 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 	 */
 	estate->es_tupleTable = NIL;
 	estate->es_trig_tuple_slot = NULL;
+	estate->es_trig_oldtup_slot = NULL;
 
 	/* mark EvalPlanQual not active */
 	estate->es_epqTuple = NULL;
@@ -911,6 +912,8 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
 
 		resultRelInfo->ri_TrigFunctions = (FmgrInfo *)
 			palloc0(n * sizeof(FmgrInfo));
+		resultRelInfo->ri_TrigWhenExprs = (List **)
+			palloc0(n * sizeof(List *));
 		if (doInstrument)
 			resultRelInfo->ri_TrigInstrument = InstrAlloc(n);
 		else
@@ -919,6 +922,7 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
 	else
 	{
 		resultRelInfo->ri_TrigFunctions = NULL;
+		resultRelInfo->ri_TrigWhenExprs = NULL;
 		resultRelInfo->ri_TrigInstrument = NULL;
 	}
 	resultRelInfo->ri_ConstraintExprs = NULL;
diff --git a/src/backend/executor/execQual.c b/src/backend/executor/execQual.c
index 226e15546fd..36b72abcce2 100644
--- a/src/backend/executor/execQual.c
+++ b/src/backend/executor/execQual.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.254 2009/11/04 22:26:05 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.255 2009/11/20 20:38:10 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -491,26 +491,15 @@ ExecEvalVar(ExprState *exprstate, ExprContext *econtext,
 	if (isDone)
 		*isDone = ExprSingleResult;
 
-	/*
-	 * Get the input slot and attribute number we want
-	 *
-	 * The asserts check that references to system attributes only appear at
-	 * the level of a relation scan; at higher levels, system attributes must
-	 * be treated as ordinary variables (since we no longer have access to the
-	 * original tuple).
-	 */
-	attnum = variable->varattno;
-
+	/* Get the input slot and attribute number we want */
 	switch (variable->varno)
 	{
 		case INNER:				/* get the tuple from the inner node */
 			slot = econtext->ecxt_innertuple;
-			Assert(attnum > 0);
 			break;
 
 		case OUTER:				/* get the tuple from the outer node */
 			slot = econtext->ecxt_outertuple;
-			Assert(attnum > 0);
 			break;
 
 		default:				/* get the tuple from the relation being
@@ -519,6 +508,8 @@ ExecEvalVar(ExprState *exprstate, ExprContext *econtext,
 			break;
 	}
 
+	attnum = variable->varattno;
+
 	if (attnum != InvalidAttrNumber)
 	{
 		/*
@@ -715,7 +706,7 @@ ExecEvalWholeRowVar(ExprState *exprstate, ExprContext *econtext,
 					bool *isNull, ExprDoneCond *isDone)
 {
 	Var		   *variable = (Var *) exprstate->expr;
-	TupleTableSlot *slot = econtext->ecxt_scantuple;
+	TupleTableSlot *slot;
 	HeapTuple	tuple;
 	TupleDesc	tupleDesc;
 	HeapTupleHeader dtuple;
@@ -724,6 +715,23 @@ ExecEvalWholeRowVar(ExprState *exprstate, ExprContext *econtext,
 		*isDone = ExprSingleResult;
 	*isNull = false;
 
+	/* Get the input slot we want */
+	switch (variable->varno)
+	{
+		case INNER:				/* get the tuple from the inner node */
+			slot = econtext->ecxt_innertuple;
+			break;
+
+		case OUTER:				/* get the tuple from the outer node */
+			slot = econtext->ecxt_outertuple;
+			break;
+
+		default:				/* get the tuple from the relation being
+								 * scanned */
+			slot = econtext->ecxt_scantuple;
+			break;
+	}
+
 	tuple = ExecFetchSlotTuple(slot);
 	tupleDesc = slot->tts_tupleDescriptor;
 
@@ -766,7 +774,7 @@ ExecEvalWholeRowSlow(ExprState *exprstate, ExprContext *econtext,
 					 bool *isNull, ExprDoneCond *isDone)
 {
 	Var		   *variable = (Var *) exprstate->expr;
-	TupleTableSlot *slot = econtext->ecxt_scantuple;
+	TupleTableSlot *slot;
 	HeapTuple	tuple;
 	TupleDesc	var_tupdesc;
 	HeapTupleHeader dtuple;
@@ -775,6 +783,23 @@ ExecEvalWholeRowSlow(ExprState *exprstate, ExprContext *econtext,
 		*isDone = ExprSingleResult;
 	*isNull = false;
 
+	/* Get the input slot we want */
+	switch (variable->varno)
+	{
+		case INNER:				/* get the tuple from the inner node */
+			slot = econtext->ecxt_innertuple;
+			break;
+
+		case OUTER:				/* get the tuple from the outer node */
+			slot = econtext->ecxt_outertuple;
+			break;
+
+		default:				/* get the tuple from the relation being
+								 * scanned */
+			slot = econtext->ecxt_scantuple;
+			break;
+	}
+
 	/*
 	 * Currently, the only case handled here is stripping of trailing resjunk
 	 * fields, which we do in a slightly chintzy way by just adjusting the
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index d3352f1f5d4..e1aa8ce8ac9 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.165 2009/10/26 02:26:29 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.166 2009/11/20 20:38:10 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -117,6 +117,7 @@ CreateExecutorState(void)
 
 	estate->es_trig_target_relations = NIL;
 	estate->es_trig_tuple_slot = NULL;
+	estate->es_trig_oldtup_slot = NULL;
 
 	estate->es_param_list_info = NULL;
 	estate->es_param_exec_vals = NULL;
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 3f1f9c093ee..33b87cb63c0 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeModifyTable.c,v 1.2 2009/10/26 02:26:31 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeModifyTable.c,v 1.3 2009/11/20 20:38:10 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -215,9 +215,10 @@ ExecInsert(TupleTableSlot *slot,
 			 * slot should not try to clear it.
 			 */
 			TupleTableSlot *newslot = estate->es_trig_tuple_slot;
+			TupleDesc tupdesc = RelationGetDescr(resultRelationDesc);
 
-			if (newslot->tts_tupleDescriptor != slot->tts_tupleDescriptor)
-				ExecSetSlotDescriptor(newslot, slot->tts_tupleDescriptor);
+			if (newslot->tts_tupleDescriptor != tupdesc)
+				ExecSetSlotDescriptor(newslot, tupdesc);
 			ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
 			slot = newslot;
 			tuple = newtuple;
@@ -467,9 +468,10 @@ ExecUpdate(ItemPointer tupleid,
 			 * slot should not try to clear it.
 			 */
 			TupleTableSlot *newslot = estate->es_trig_tuple_slot;
+			TupleDesc tupdesc = RelationGetDescr(resultRelationDesc);
 
-			if (newslot->tts_tupleDescriptor != slot->tts_tupleDescriptor)
-				ExecSetSlotDescriptor(newslot, slot->tts_tupleDescriptor);
+			if (newslot->tts_tupleDescriptor != tupdesc)
+				ExecSetSlotDescriptor(newslot, tupdesc);
 			ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
 			slot = newslot;
 			tuple = newtuple;