Set ecxt_scantuple correctly for tuple routing.

In 2ac3ef7a01df859c62d0a02333b646d65eaec5ff, we changed things so that
it's possible for a different TupleTableSlot to be used for partitioned
tables at successively lower levels.  If we do end up changing the slot
from the original, we must update ecxt_scantuple to point to the new one
for partition key of the tuple to be computed correctly.

Reported by Rajkumar Raghuwanshi.  Patch by Amit Langote.

Discussion: http://postgr.es/m/CAKcux6%3Dm1qyqB2k6cjniuMMrYXb75O-MB4qGQMu8zg-iGGLjDw%40mail.gmail.com

src/backend/catalog/partition.c

@@ -1679,7 +1679,10 @@ get_partition_for_tuple(PartitionDispatch *pd,
 	bool		isnull[PARTITION_MAX_KEYS];
 	int			cur_offset,
 				cur_index;
-	int			i;
+	int			i,
+				result;
+	ExprContext *ecxt = GetPerTupleExprContext(estate);
+	TupleTableSlot *ecxt_scantuple_old = ecxt->ecxt_scantuple;
 
 	/* start with the root partitioned table */
 	parent = pd[0];
@@ -1708,7 +1711,15 @@ get_partition_for_tuple(PartitionDispatch *pd,
 			slot = myslot;
 		}
 
-		/* Extract partition key from tuple */
+		/*
+		 * Extract partition key from tuple. Expression evaluation machinery
+		 * that FormPartitionKeyDatum() invokes expects ecxt_scantuple to
+		 * point to the correct tuple slot.  The slot might have changed from
+		 * what was used for the parent table if the table of the current
+		 * partitioning level has different tuple descriptor from the parent.
+		 * So update ecxt_scantuple accordingly.
+		 */
+		ecxt->ecxt_scantuple = slot;
 		FormPartitionKeyDatum(parent, slot, estate, values, isnull);
 
 		if (key->strategy == PARTITION_STRATEGY_RANGE)
@@ -1763,16 +1774,21 @@ get_partition_for_tuple(PartitionDispatch *pd,
 		 */
 		if (cur_index < 0)
 		{
+			result = -1;
 			*failed_at = RelationGetRelid(parent->reldesc);
-			return -1;
-		}
-		else if (parent->indexes[cur_index] < 0)
-			parent = pd[-parent->indexes[cur_index]];
-		else
 			break;
+		}
+		else if (parent->indexes[cur_index] >= 0)
+		{
+			result = parent->indexes[cur_index];
+			break;
+		}
+		else
+			parent = pd[-parent->indexes[cur_index]];
 	}
 
-	return parent->indexes[cur_index];
+	ecxt->ecxt_scantuple = ecxt_scantuple_old;
+	return result;
 }
 
 /*

src/backend/executor/execMain.c

@@ -3192,9 +3192,7 @@ ExecFindPartition(ResultRelInfo *resultRelInfo, PartitionDispatch *pd,
 {
 	int			result;
 	Oid			failed_at;
-	ExprContext *econtext = GetPerTupleExprContext(estate);
 
-	econtext->ecxt_scantuple = slot;
 	result = get_partition_for_tuple(pd, slot, estate, &failed_at);
 	if (result < 0)
 	{

src/test/regress/expected/insert.out

@@ -320,7 +320,7 @@ drop table part_ee_ff, part_gg2_2, part_gg2_1, part_gg2, part_gg1, part_gg;
 drop table part_aa_bb, part_cc_dd, part_null, list_parted;
 -- more tests for certain multi-level partitioning scenarios
 create table p (a int, b int) partition by range (a, b);
-create table p1 (b int, a int not null) partition by range (b);
+create table p1 (b int not null, a int not null) partition by range ((b+0));
 create table p11 (like p1);
 alter table p11 drop a;
 alter table p11 add a int;

src/test/regress/sql/insert.sql

@@ -193,7 +193,7 @@ drop table part_aa_bb, part_cc_dd, part_null, list_parted;
 
 -- more tests for certain multi-level partitioning scenarios
 create table p (a int, b int) partition by range (a, b);
-create table p1 (b int, a int not null) partition by range (b);
+create table p1 (b int not null, a int not null) partition by range ((b+0));
 create table p11 (like p1);
 alter table p11 drop a;
 alter table p11 add a int;