postgres_fdw: Avoid 'variable not found in subplan target list' error.

The tlist of the EvalPlanQual outer plan for a ForeignScan node is
adjusted to produce a tuple whose descriptor matches the scan tuple slot
for the ForeignScan node.  But in the case where the outer plan contains
an extra Sort node, if the new tlist contained columns required only for
evaluating PlaceHolderVars or columns required only for evaluating local
conditions, this would cause setrefs.c to fail with the error.

The cause of this is that when creating the outer plan by injecting the
Sort node into an alternative local join plan that could emit such extra
columns as well, we fail to arrange for the outer plan to propagate them
up through the Sort node, causing setrefs.c to fail to match up them in
the new tlist to what is available from the outer plan.  Repair.

Per report from Alexander Pyhalov.

Richard Guo and Etsuro Fujita, reviewed by Alexander Pyhalov and Tom Lane.
Backpatch to all supported versions.

Discussion: http://postgr.es/m/cfb17bf6dfdf876467bd5ef533852d18%40postgrespro.ru

1 files changed, 13 insertions, 0 deletions

diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 42735ae78a9..9a493502f1e 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -672,6 +672,19 @@ SELECT * FROM ft1, ft2, ft4, ft5, local_tbl WHERE ft1.c1 = ft2.c1 AND ft1.c2 = f
     AND ft1.c2 = ft5.c1 AND ft1.c2 = local_tbl.c1 AND ft1.c1 < 100 AND ft2.c1 < 100 FOR UPDATE;
 RESET enable_nestloop;
 RESET enable_hashjoin;
+
+-- test that add_paths_with_pathkeys_for_rel() arranges for the epq_path to
+-- return columns needed by the parent ForeignScan node
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT * FROM local_tbl LEFT JOIN (SELECT ft1.*, COALESCE(ft1.c3 || ft2.c3, 'foobar') FROM ft1 INNER JOIN ft2 ON (ft1.c1 = ft2.c1 AND ft1.c1 < 100)) ss ON (local_tbl.c1 = ss.c1) ORDER BY local_tbl.c1 FOR UPDATE OF local_tbl;
+
+ALTER SERVER loopback OPTIONS (DROP extensions);
+ALTER SERVER loopback OPTIONS (ADD fdw_startup_cost '10000.0');
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT * FROM local_tbl LEFT JOIN (SELECT ft1.* FROM ft1 INNER JOIN ft2 ON (ft1.c1 = ft2.c1 AND ft1.c1 < 100 AND ft1.c1 = postgres_fdw_abs(ft2.c2))) ss ON (local_tbl.c3 = ss.c3) ORDER BY local_tbl.c1 FOR UPDATE OF local_tbl;
+ALTER SERVER loopback OPTIONS (DROP fdw_startup_cost);
+ALTER SERVER loopback OPTIONS (ADD extensions 'postgres_fdw');
+
 DROP TABLE local_tbl;
 
 -- check join pushdown in situations where multiple userids are involved