Re-allow FDWs and custom scan providers to replace joins with pseudoconstant quals.

This was disabled in commit 6f80a8d9c due to the lack of support for
handling of pseudoconstant quals assigned to replaced joins in
createplan.c.  To re-allow it, this patch adds the support by 1)
modifying the ForeignPath and CustomPath structs so that if they
represent foreign and custom scans replacing a join with a scan, they
store the list of RestrictInfo nodes to apply to the join, as in
JoinPaths, and by 2) modifying create_scan_plan() in createplan.c so
that it uses that list in that case, instead of the baserestrictinfo
list, to get pseudoconstant quals assigned to the join, as mentioned in
the commit message for that commit.

Important item for the release notes: this is non-backwards-compatible
since it modifies the ForeignPath and CustomPath structs, as mentioned
above, and changes the argument lists for FDW helper functions
create_foreignscan_path(), create_foreign_join_path(), and
create_foreign_upper_path().

Richard Guo, with some additional changes by me, reviewed by Nishant
Sharma, Suraj Kharage, and Richard Guo.

Discussion: https://postgr.es/m/CADrsxdbcN1vejBaf8a%2BQhrZY5PXL-04mCd4GDu6qm6FigDZd6Q%40mail.gmail.com

1 files changed, 15 insertions, 5 deletions

diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index c5cada55fb7..ef58b8b0ea2 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -524,7 +524,7 @@ static List *get_useful_pathkeys_for_relation(PlannerInfo *root,
 											  RelOptInfo *rel);
 static List *get_useful_ecs_for_relation(PlannerInfo *root, RelOptInfo *rel);
 static void add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel,
-											Path *epq_path);
+											Path *epq_path, List *restrictlist);
 static void add_foreign_grouping_paths(PlannerInfo *root,
 									   RelOptInfo *input_rel,
 									   RelOptInfo *grouped_rel,
@@ -1034,11 +1034,12 @@ postgresGetForeignPaths(PlannerInfo *root,
 								   NIL, /* no pathkeys */
 								   baserel->lateral_relids,
 								   NULL,	/* no extra plan */
+								   NIL, /* no fdw_restrictinfo list */
 								   NIL);	/* no fdw_private list */
 	add_path(baserel, (Path *) path);
 
 	/* Add paths with pathkeys */
-	add_paths_with_pathkeys_for_rel(root, baserel, NULL);
+	add_paths_with_pathkeys_for_rel(root, baserel, NULL, NIL);
 
 	/*
 	 * If we're not using remote estimates, stop here.  We have no way to
@@ -1206,6 +1207,7 @@ postgresGetForeignPaths(PlannerInfo *root,
 									   NIL, /* no pathkeys */
 									   param_info->ppi_req_outer,
 									   NULL,
+									   NIL, /* no fdw_restrictinfo list */
 									   NIL);	/* no fdw_private list */
 		add_path(baserel, (Path *) path);
 	}
@@ -5991,7 +5993,7 @@ foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype,
 
 static void
 add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel,
-								Path *epq_path)
+								Path *epq_path, List *restrictlist)
 {
 	List	   *useful_pathkeys_list = NIL; /* List of all pathkeys */
 	ListCell   *lc;
@@ -6085,6 +6087,7 @@ add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel,
 											 useful_pathkeys,
 											 rel->lateral_relids,
 											 sorted_epq_path,
+											 NIL,	/* no fdw_restrictinfo list */
 											 NIL));
 		else
 			add_path(rel, (Path *)
@@ -6096,6 +6099,7 @@ add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel,
 											  useful_pathkeys,
 											  rel->lateral_relids,
 											  sorted_epq_path,
+											  restrictlist,
 											  NIL));
 	}
 }
@@ -6348,13 +6352,15 @@ postgresGetForeignJoinPaths(PlannerInfo *root,
 										NIL,	/* no pathkeys */
 										joinrel->lateral_relids,
 										epq_path,
+										extra->restrictlist,
 										NIL);	/* no fdw_private */
 
 	/* Add generated path into joinrel by add_path(). */
 	add_path(joinrel, (Path *) joinpath);
 
 	/* Consider pathkeys for the join relation */
-	add_paths_with_pathkeys_for_rel(root, joinrel, epq_path);
+	add_paths_with_pathkeys_for_rel(root, joinrel, epq_path,
+									extra->restrictlist);
 
 	/* XXX Consider parameterized paths for the join relation */
 }
@@ -6735,6 +6741,7 @@ add_foreign_grouping_paths(PlannerInfo *root, RelOptInfo *input_rel,
 										  total_cost,
 										  NIL,	/* no pathkeys */
 										  NULL,
+										  NIL,	/* no fdw_restrictinfo list */
 										  NIL); /* no fdw_private */
 
 	/* Add generated path into grouped_rel by add_path(). */
@@ -6868,6 +6875,7 @@ add_foreign_ordered_paths(PlannerInfo *root, RelOptInfo *input_rel,
 											 total_cost,
 											 root->sort_pathkeys,
 											 NULL,	/* no extra plan */
+											 NIL,	/* no fdw_restrictinfo list */
 											 fdw_private);
 
 	/* and add it to the ordered_rel */
@@ -6983,7 +6991,8 @@ add_foreign_final_paths(PlannerInfo *root, RelOptInfo *input_rel,
 													   path->total_cost,
 													   path->pathkeys,
 													   NULL,	/* no extra plan */
-													   NULL);	/* no fdw_private */
+													   NIL,	/* no fdw_restrictinfo list */
+													   NIL);	/* no fdw_private */
 
 				/* and add it to the final_rel */
 				add_path(final_rel, (Path *) final_path);
@@ -7103,6 +7112,7 @@ add_foreign_final_paths(PlannerInfo *root, RelOptInfo *input_rel,
 										   total_cost,
 										   pathkeys,
 										   NULL,	/* no extra plan */
+										   NIL,	/* no fdw_restrictinfo list */
 										   fdw_private);
 
 	/* and add it to the final_rel */