Factor error generation out of ExecPartitionCheck.

At present, we always raise an ERROR if the partition constraint
is violated, but a pending patch for UPDATE tuple routing will
consider instead moving the tuple to the correct partition.
Refactor to make that simpler.

Amit Khandekar, reviewed by Amit Langote, David Rowley, and me.

Discussion: http://postgr.es/m/CAJ3gD9cue54GbEzfV-61nyGpijvjZgCcghvLsB0_nL8Nm8HzCA@mail.gmail.com

src/backend/commands/copy.c

@@ -2731,7 +2731,7 @@ CopyFrom(CopyState cstate)
 
 				/* Check the constraints of the tuple */
 				if (cstate->rel->rd_att->constr || check_partition_constr)
-					ExecConstraints(resultRelInfo, slot, estate);
+					ExecConstraints(resultRelInfo, slot, estate, true);
 
 				if (useHeapMultiInsert)
 				{

src/backend/executor/execMain.c

@@ -1849,16 +1849,12 @@ ExecRelCheck(ResultRelInfo *resultRelInfo,
  * ExecPartitionCheck --- check that tuple meets the partition constraint.
  *
  * Exported in executor.h for outside use.
+ * Returns true if it meets the partition constraint, else returns false.
  */
-void
+bool
 ExecPartitionCheck(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 				   EState *estate)
 {
-	Relation	rel = resultRelInfo->ri_RelationDesc;
-	TupleDesc	tupdesc = RelationGetDescr(rel);
-	Bitmapset  *modifiedCols;
-	Bitmapset  *insertedCols;
-	Bitmapset  *updatedCols;
 	ExprContext *econtext;
 
 	/*
@@ -1886,12 +1882,30 @@ ExecPartitionCheck(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 	 * As in case of the catalogued constraints, we treat a NULL result as
 	 * success here, not a failure.
 	 */
-	if (!ExecCheck(resultRelInfo->ri_PartitionCheckExpr, econtext))
+	return ExecCheck(resultRelInfo->ri_PartitionCheckExpr, econtext);
+}
+
+/*
+ * ExecPartitionCheckEmitError - Form and emit an error message after a failed
+ * partition constraint check.
+ */
+void
+ExecPartitionCheckEmitError(ResultRelInfo *resultRelInfo,
+							TupleTableSlot *slot,
+							EState *estate)
 {
-		char	   *val_desc;
+	Relation	rel = resultRelInfo->ri_RelationDesc;
 	Relation	orig_rel = rel;
+	TupleDesc	tupdesc = RelationGetDescr(rel);
+	char	   *val_desc;
+	Bitmapset  *modifiedCols;
+	Bitmapset  *insertedCols;
+	Bitmapset  *updatedCols;
 
-		/* See the comment above. */
+	/*
+	 * Need to first convert the tuple to the root partitioned table's row
+	 * type. For details, check similar comments in ExecConstraints().
+	 */
 	if (resultRelInfo->ri_PartitionRoot)
 	{
 		HeapTuple	tuple = ExecFetchSlotTuple(slot);
@@ -1925,13 +1939,12 @@ ExecPartitionCheck(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 					RelationGetRelationName(orig_rel)),
 			 val_desc ? errdetail("Failing row contains %s.", val_desc) : 0));
 }
-}
 
 /*
  * ExecConstraints - check constraints of the tuple in 'slot'
  *
- * This checks the traditional NOT NULL and check constraints, as well as
- * the partition constraint, if any.
+ * This checks the traditional NOT NULL and check constraints, and if
+ * requested, checks the partition constraint.
  *
  * Note: 'slot' contains the tuple to check the constraints of, which may
  * have been converted from the original input tuple after tuple routing.
@@ -1939,7 +1952,8 @@ ExecPartitionCheck(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
  */
 void
 ExecConstraints(ResultRelInfo *resultRelInfo,
-				TupleTableSlot *slot, EState *estate)
+				TupleTableSlot *slot, EState *estate,
+				bool check_partition_constraint)
 {
 	Relation	rel = resultRelInfo->ri_RelationDesc;
 	TupleDesc	tupdesc = RelationGetDescr(rel);
@@ -2055,8 +2069,9 @@ ExecConstraints(ResultRelInfo *resultRelInfo,
 		}
 	}
 
-	if (resultRelInfo->ri_PartitionCheck)
-		ExecPartitionCheck(resultRelInfo, slot, estate);
+	if (check_partition_constraint && resultRelInfo->ri_PartitionCheck &&
+		!ExecPartitionCheck(resultRelInfo, slot, estate))
+		ExecPartitionCheckEmitError(resultRelInfo, slot, estate);
 }
 
 

src/backend/executor/execPartition.c

@@ -167,8 +167,9 @@ ExecFindPartition(ResultRelInfo *resultRelInfo, PartitionDispatch *pd,
 	 * First check the root table's partition constraint, if any.  No point in
 	 * routing the tuple if it doesn't belong in the root table itself.
 	 */
-	if (resultRelInfo->ri_PartitionCheck)
-		ExecPartitionCheck(resultRelInfo, slot, estate);
+	if (resultRelInfo->ri_PartitionCheck &&
+		!ExecPartitionCheck(resultRelInfo, slot, estate))
+		ExecPartitionCheckEmitError(resultRelInfo, slot, estate);
 
 	/* start with the root partitioned table */
 	parent = pd[0];

src/backend/executor/execReplication.c

@@ -401,7 +401,7 @@ ExecSimpleRelationInsert(EState *estate, TupleTableSlot *slot)
 
 		/* Check the constraints of the tuple */
 		if (rel->rd_att->constr)
-			ExecConstraints(resultRelInfo, slot, estate);
+			ExecConstraints(resultRelInfo, slot, estate, true);
 
 		/* Store the slot into tuple that we can inspect. */
 		tuple = ExecMaterializeSlot(slot);
@@ -466,7 +466,7 @@ ExecSimpleRelationUpdate(EState *estate, EPQState *epqstate,
 
 		/* Check the constraints of the tuple */
 		if (rel->rd_att->constr)
-			ExecConstraints(resultRelInfo, slot, estate);
+			ExecConstraints(resultRelInfo, slot, estate, true);
 
 		/* Store the slot into tuple that we can write. */
 		tuple = ExecMaterializeSlot(slot);

src/backend/executor/nodeModifyTable.c

@@ -487,7 +487,7 @@ ExecInsert(ModifyTableState *mtstate,
 
 		/* Check the constraints of the tuple */
 		if (resultRelationDesc->rd_att->constr || check_partition_constr)
-			ExecConstraints(resultRelInfo, slot, estate);
+			ExecConstraints(resultRelInfo, slot, estate, true);
 
 		if (onconflict != ONCONFLICT_NONE && resultRelInfo->ri_NumIndices > 0)
 		{
@@ -1049,7 +1049,7 @@ lreplace:;
 		 * tuple-routing is performed here, hence the slot remains unchanged.
 		 */
 		if (resultRelationDesc->rd_att->constr || resultRelInfo->ri_PartitionCheck)
-			ExecConstraints(resultRelInfo, slot, estate);
+			ExecConstraints(resultRelInfo, slot, estate, true);
 
 		/*
 		 * replace the heap tuple

src/include/executor/executor.h

@@ -187,8 +187,11 @@ extern ResultRelInfo *ExecGetTriggerResultRel(EState *estate, Oid relid);
 extern void ExecCleanUpTriggerState(EState *estate);
 extern bool ExecContextForcesOids(PlanState *planstate, bool *hasoids);
 extern void ExecConstraints(ResultRelInfo *resultRelInfo,
+				TupleTableSlot *slot, EState *estate,
+				bool check_partition_constraint);
+extern bool ExecPartitionCheck(ResultRelInfo *resultRelInfo,
 				   TupleTableSlot *slot, EState *estate);
-extern void ExecPartitionCheck(ResultRelInfo *resultRelInfo,
+extern void ExecPartitionCheckEmitError(ResultRelInfo *resultRelInfo,
 									TupleTableSlot *slot, EState *estate);
 extern void ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
 					 TupleTableSlot *slot, EState *estate);