Improve handling of CustomPath/CustomPlan(State) children.

Allow CustomPath to have a list of paths, CustomPlan a list of plans,
and CustomPlanState a list of planstates known to the core system, so
that custom path/plan providers can more reasonably use this
infrastructure for nodes with multiple children.

KaiGai Kohei, per a design suggestion from Tom Lane, with some
further kibitzing by me.

3 files changed, 5 insertions, 1 deletions

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index db5bd7faf0..541ee18735 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1616,6 +1616,7 @@ typedef struct CustomScanState
 {
 	ScanState	ss;
 	uint32		flags;			/* mask of CUSTOMPATH_* flags, see relation.h */
+	List	   *custom_ps;		/* list of child PlanState nodes, if any */
 	const CustomExecMethods *methods;
 } CustomScanState;
 
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index d967219c0b..5f538f3e8c 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -550,6 +550,7 @@ typedef struct CustomScan
 {
 	Scan		scan;
 	uint32		flags;			/* mask of CUSTOMPATH_* flags, see relation.h */
+	List	   *custom_plans;	/* list of Plan nodes, if any */
 	List	   *custom_exprs;	/* expressions that custom code may evaluate */
 	List	   *custom_private; /* private data for custom code */
 	List	   *custom_scan_tlist;		/* optional tlist describing scan
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 33b0874570..cb916ea8e1 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -929,7 +929,8 @@ typedef struct CustomPathMethods
 												RelOptInfo *rel,
 												struct CustomPath *best_path,
 												List *tlist,
-												List *clauses);
+												List *clauses,
+												List *custom_plans);
 	/* Optional: print additional fields besides "private" */
 	void		(*TextOutCustomPath) (StringInfo str,
 											  const struct CustomPath *node);
@@ -939,6 +940,7 @@ typedef struct CustomPath
 {
 	Path		path;
 	uint32		flags;			/* mask of CUSTOMPATH_* flags, see above */
+	List	   *custom_paths;	/* list of child Path nodes, if any */
 	List	   *custom_private;
 	const CustomPathMethods *methods;
 } CustomPath;