Redesign PlanForeignScan API to allow multiple paths for a foreign table.

The original API specification only allowed an FDW to create a single
access path, which doesn't seem like a terribly good idea in hindsight.
Instead, move the responsibility for building the Path node and calling
add_path() into the FDW's PlanForeignScan function.  Now, it can do that
more than once if appropriate.  There is no longer any need for the
transient FdwPlan struct, so get rid of that.

Etsuro Fujita, Shigeru Hanada, Tom Lane

1 files changed, 8 insertions, 4 deletions

diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 8f034176e7c..6e81ce0fc26 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -18,6 +18,7 @@
 #include <math.h>
 
 #include "catalog/pg_class.h"
+#include "foreign/fdwapi.h"
 #include "nodes/nodeFuncs.h"
 #ifdef OPTIMIZER_DEBUG
 #include "nodes/print.h"
@@ -399,15 +400,18 @@ set_foreign_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 
 /*
  * set_foreign_pathlist
- *		Build the (single) access path for a foreign table RTE
+ *		Build access paths for a foreign table RTE
  */
 static void
 set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 {
-	/* Generate appropriate path */
-	add_path(rel, (Path *) create_foreignscan_path(root, rel));
+	FdwRoutine *fdwroutine;
 
-	/* Select cheapest path (pretty easy in this case...) */
+	/* Call the FDW's PlanForeignScan function to generate path(s) */
+	fdwroutine = GetFdwRoutineByRelId(rte->relid);
+	fdwroutine->PlanForeignScan(rte->relid, root, rel);
+
+	/* Select cheapest path */
 	set_cheapest(rel);
 }