Prevent generation of bogus subquery scan paths.

Commit 0927d2f46ddd4cf7d6bf2cc84b3be923e0aedc52 didn't check that
consider_parallel was set for the target relation or account for
the possibility that required_outer might be non-empty.

To prevent future bugs of this ilk, add some assertions to
add_partial_path and do a bit of future-proofing of the code
recently added to recurse_set_operations.

Report by Andreas Seltenreich.  Patch by Jeevan Chalke.  Review
by Amit Kapila and by me.

Discussion: http://postgr.es/m/CAM2+6=U+9otsyF2fYB8x_2TBeHTR90itarqW=qAEjN-kHaC7kw@mail.gmail.com

1 files changed, 23 insertions, 18 deletions

diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 9ed73da0f79..afc663cfd8f 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -2243,26 +2243,31 @@ set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
 										  pathkeys, required_outer));
 	}
 
-	/* If consider_parallel is false, there should be no partial paths. */
-	Assert(sub_final_rel->consider_parallel ||
-		   sub_final_rel->partial_pathlist == NIL);
-
-	/* Same for partial paths. */
-	foreach(lc, sub_final_rel->partial_pathlist)
+	/* If outer rel allows parallelism, do same for partial paths. */
+	if (rel->consider_parallel && bms_is_empty(required_outer))
 	{
-		Path	   *subpath = (Path *) lfirst(lc);
-		List	   *pathkeys;
-
-		/* Convert subpath's pathkeys to outer representation */
-		pathkeys = convert_subquery_pathkeys(root,
-											 rel,
-											 subpath->pathkeys,
-											 make_tlist_from_pathtarget(subpath->pathtarget));
+		/* If consider_parallel is false, there should be no partial paths. */
+		Assert(sub_final_rel->consider_parallel ||
+			   sub_final_rel->partial_pathlist == NIL);
 
-		/* Generate outer path using this subpath */
-		add_partial_path(rel, (Path *)
-						 create_subqueryscan_path(root, rel, subpath,
-												  pathkeys, required_outer));
+		/* Same for partial paths. */
+		foreach(lc, sub_final_rel->partial_pathlist)
+		{
+			Path	   *subpath = (Path *) lfirst(lc);
+			List	   *pathkeys;
+
+			/* Convert subpath's pathkeys to outer representation */
+			pathkeys = convert_subquery_pathkeys(root,
+												 rel,
+												 subpath->pathkeys,
+												 make_tlist_from_pathtarget(subpath->pathtarget));
+
+			/* Generate outer path using this subpath */
+			add_partial_path(rel, (Path *)
+							 create_subqueryscan_path(root, rel, subpath,
+													  pathkeys,
+													  required_outer));
+		}
 	}
 }