Invalidate cached plans on FDW option changes.

This fixes problems where a plan must change but fails to do so,
as seen in a bug report from Rajkumar Raghuwanshi.

For ALTER FOREIGN TABLE OPTIONS, do this through the standard method of
forcing a relcache flush on the table.  For ALTER FOREIGN DATA WRAPPER
and ALTER SERVER, just flush the whole plan cache on any change in
pg_foreign_data_wrapper or pg_foreign_server.  That matches the way
we handle some other low-probability cases such as opclass changes, and
it's unclear that the case arises often enough to be worth working harder.
Besides, that gives a patch that is simple enough to back-patch with
confidence.

Back-patch to 9.3.  In principle we could apply the code change to 9.2 as
well, but (a) we lack postgres_fdw to test it with, (b) it's doubtful that
anyone is doing anything exciting enough with FDWs that far back to need
this desperately, and (c) the patch doesn't apply cleanly.

Patch originally by Amit Langote, reviewed by Etsuro Fujita and Ashutosh
Bapat, who each contributed substantial changes as well.

Discussion: https://postgr.es/m/CAKcux6m5cA6rRPTKkqVdJ-R=KKDfe35Q_ZuUqxDSV_4hwga=og@mail.gmail.com

1 files changed, 23 insertions, 0 deletions

diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index f48743c390d..919177649ed 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -881,12 +881,35 @@ EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st5('foo', 1);
 EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st5('foo', 1);
 EXECUTE st5('foo', 1);
 
+-- altering FDW options requires replanning
+PREPARE st6 AS SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st6;
+PREPARE st7 AS INSERT INTO ft1 (c1,c2,c3) VALUES (1001,101,'foo');
+EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st7;
+ALTER TABLE "S 1"."T 1" RENAME TO "T 0";
+ALTER FOREIGN TABLE ft1 OPTIONS (SET table_name 'T 0');
+EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st6;
+EXECUTE st6;
+EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st7;
+ALTER TABLE "S 1"."T 0" RENAME TO "T 1";
+ALTER FOREIGN TABLE ft1 OPTIONS (SET table_name 'T 1');
+
+PREPARE st8 AS SELECT count(c3) FROM ft1 t1 WHERE t1.c1 === t1.c2;
+EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st8;
+ALTER SERVER loopback OPTIONS (DROP extensions);
+EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st8;
+EXECUTE st8;
+ALTER SERVER loopback OPTIONS (ADD extensions 'postgres_fdw');
+
 -- cleanup
 DEALLOCATE st1;
 DEALLOCATE st2;
 DEALLOCATE st3;
 DEALLOCATE st4;
 DEALLOCATE st5;
+DEALLOCATE st6;
+DEALLOCATE st7;
+DEALLOCATE st8;
 
 -- System columns, except ctid and oid, should not be sent to remote
 EXPLAIN (VERBOSE, COSTS OFF)