Generalize ri_RootToPartitionMap to use for non-partition children

ri_RootToPartitionMap is currently only initialized for tuple routing
target partitions, though a future commit will need the ability to use
it even for the non-partition child tables, so make adjustments to the
decouple it from the partitioning code.

Also, make it lazily initialized via ExecGetRootToChildMap(), making
that function its preferred access path.  Existing third-party code
accessing it directly should no longer do so; consequently, it's been
renamed to ri_RootToChildMap, which also makes it consistent with
ri_ChildToRootMap.

ExecGetRootToChildMap() houses the logic of setting the map appropriately
depending on whether a given child relation is partition or not.

To support this, also add a separate entry point for TupleConversionMap
creation that receives an AttrMap.  No new code here, just split an
existing function in two.

Author: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/CA+HiwqEYUhDXSK5BTvG_xk=eaAEJCD4GS3C6uH7ybBvv+Z_Tmg@mail.gmail.com

1 files changed, 17 insertions, 2 deletions

diff --git a/src/backend/access/common/tupconvert.c b/src/backend/access/common/tupconvert.c
index b2f892d2fdf..4023f533d74 100644
--- a/src/backend/access/common/tupconvert.c
+++ b/src/backend/access/common/tupconvert.c
@@ -102,9 +102,7 @@ TupleConversionMap *
 convert_tuples_by_name(TupleDesc indesc,
 					   TupleDesc outdesc)
 {
-	TupleConversionMap *map;
 	AttrMap    *attrMap;
-	int			n = outdesc->natts;
 
 	/* Verify compatibility and prepare attribute-number map */
 	attrMap = build_attrmap_by_name_if_req(indesc, outdesc, false);
@@ -115,6 +113,23 @@ convert_tuples_by_name(TupleDesc indesc,
 		return NULL;
 	}
 
+	return convert_tuples_by_name_attrmap(indesc, outdesc, attrMap);
+}
+
+/*
+ * Set up tuple conversion for input and output TupleDescs using the given
+ * AttrMap.
+ */
+TupleConversionMap *
+convert_tuples_by_name_attrmap(TupleDesc indesc,
+							   TupleDesc outdesc,
+							   AttrMap *attrMap)
+{
+	int			n = outdesc->natts;
+	TupleConversionMap *map;
+
+	Assert(attrMap != NULL);
+
 	/* Prepare the map structure */
 	map = (TupleConversionMap *) palloc(sizeof(TupleConversionMap));
 	map->indesc = indesc;