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, 13 deletions

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index a2008846c63..71248a94660 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -539,6 +539,21 @@ typedef struct ResultRelInfo
 	ExprState  *ri_PartitionCheckExpr;
 
 	/*
+	 * Map to convert child result relation tuples to the format of the table
+	 * actually mentioned in the query (called "root").  Computed only if
+	 * needed.  A NULL map value indicates that no conversion is needed, so we
+	 * must have a separate flag to show if the map has been computed.
+	 */
+	TupleConversionMap *ri_ChildToRootMap;
+	bool		ri_ChildToRootMapValid;
+
+	/*
+	 * As above, but in the other direction.
+	 */
+	TupleConversionMap *ri_RootToChildMap;
+	bool		ri_RootToChildMapValid;
+
+	/*
 	 * Information needed by tuple routing target relations
 	 *
 	 * RootResultRelInfo gives the target relation mentioned in the query, if
@@ -546,23 +561,12 @@ typedef struct ResultRelInfo
 	 * mentioned in the query is an inherited table, nor when tuple routing is
 	 * not needed.
 	 *
-	 * RootToPartitionMap and PartitionTupleSlot, initialized by
-	 * ExecInitRoutingInfo, are non-NULL if partition has a different tuple
-	 * format than the root table.
+	 * PartitionTupleSlot is non-NULL if RootToChild conversion is needed and
+	 * the relation is a partition.
 	 */
 	struct ResultRelInfo *ri_RootResultRelInfo;
-	TupleConversionMap *ri_RootToPartitionMap;
 	TupleTableSlot *ri_PartitionTupleSlot;
 
-	/*
-	 * Map to convert child result relation tuples to the format of the table
-	 * actually mentioned in the query (called "root").  Computed only if
-	 * needed.  A NULL map value indicates that no conversion is needed, so we
-	 * must have a separate flag to show if the map has been computed.
-	 */
-	TupleConversionMap *ri_ChildToRootMap;
-	bool		ri_ChildToRootMapValid;
-
 	/* for use by copyfrom.c when performing multi-inserts */
 	struct CopyMultiInsertBuffer *ri_CopyMultiInsertBuffer;