Actually, I hadn't realized that the originally submitted patch had the
test in postgres_fdw only, but we really want it to catch any FDW, so it
needs to be somewhere more general. The best place I found to put this
test is in make_modifytable ... I searched for some earlier place in the
planner to do it, but couldn't find anything.
So what do people think about this?
--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
"La grandeza es una experiencia transitoria. Nunca es consistente.
Depende en gran parte de la imaginación humana creadora de mitos"
(Irulan)
>From 09fba6a6f4caf2a987aa7ee5d77dbf74372ad1d0 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvhe...@alvh.no-ip.org>
Date: Fri, 14 Oct 2022 11:19:10 +0200
Subject: [PATCH v2] Disallow MERGE cleanly for foreign partitions
---
.../postgres_fdw/expected/postgres_fdw.out | 4 ++++
contrib/postgres_fdw/sql/postgres_fdw.sql | 3 +++
src/backend/optimizer/plan/createplan.c | 20 +++++++++++++++++++
3 files changed, 27 insertions(+)
diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 9746998751..bdeba8c291 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8284,6 +8284,10 @@ select tableoid::regclass, * FROM remp2;
(3 rows)
delete from itrtest;
+-- MERGE ought to fail cleanly
+merge into itrtest using (select 1, 'foo') on (true) when matched then do nothing;
+ERROR: cannot execute MERGE on relation "remp1"
+DETAIL: This operation is not supported for foreign tables.
create unique index loct1_idx on loct1 (a);
-- DO NOTHING without an inference specification is supported
insert into itrtest values (1, 'foo') on conflict do nothing returning *;
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 1962051e54..514df43b06 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2207,6 +2207,9 @@ select tableoid::regclass, * FROM remp2;
delete from itrtest;
+-- MERGE ought to fail cleanly
+merge into itrtest using (select 1, 'foo') on (true) when matched then do nothing;
+
create unique index loct1_idx on loct1 (a);
-- DO NOTHING without an inference specification is supported
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index ab4d8e201d..ac86ce9003 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -7078,12 +7078,32 @@ make_modifytable(PlannerInfo *root, Plan *subplan,
RelOptInfo *resultRel = root->simple_rel_array[rti];
fdwroutine = resultRel->fdwroutine;
+
+ /*
+ * MERGE is not currently supported for foreign tables and we
+ * already checked when the table mentioned in the query is
+ * foreign; but we can still get here if a partitioned table has a
+ * foreign table as partition. Disallow that now, to avoid an
+ * uglier error message later.
+ */
+ if (operation == CMD_MERGE && fdwroutine != NULL)
+ {
+ RangeTblEntry *rte = root->simple_rte_array[rti];
+
+ ereport(ERROR,
+ errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("cannot execute MERGE on relation \"%s\"",
+ get_rel_name(rte->relid)),
+ errdetail_relkind_not_supported(rte->relkind));
+ }
+
}
else
{
RangeTblEntry *rte = planner_rt_fetch(rti, root);
Assert(rte->rtekind == RTE_RELATION);
+ Assert(operation != CMD_MERGE);
if (rte->relkind == RELKIND_FOREIGN_TABLE)
fdwroutine = GetFdwRoutineByRelId(rte->relid);
else
--
2.30.2
