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Prevent asynchronous execution of direct foreign-table modifications.

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Commits 27e1f1456 and 86dc90056, which were independently discussed,
cause a crash when executing an inherited foreign UPDATE/DELETE query
with asynchronous execution enabled, where children of an Append node
that is the direct/indirect child of the ModifyTable node are rewritten
so as to modify foreign tables directly by postgresPlanDirectModify();
as in that case the direct modifications are executed asynchronously,
which is not currently supported by asynchronous execution.  Fix by
disabling asynchronous execution of the direct modifications in that
function.

Author: Etsuro Fujita
Reviewed-by: Amit Langote
Discussion: https://postgr.es/m/CAPmGK158e9sJOfuWxfn%2B0ynrspXQU3JhNjSCbaoeSzMvnga%2Bbw%40mail.gmail.com
This commit is contained in:
Etsuro Fujita 2021-05-13 20:00:00 +09:00
parent 5a73a9e3b5
commit a784859f44
3 changed files with 70 additions and 0 deletions
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55
contrib/postgres_fdw/expected/postgres_fdw.out
View File

@ -10154,6 +10154,61 @@ DROP TABLE base_tbl3;
DROP TABLE base_tbl4;
RESET enable_mergejoin;
RESET enable_hashjoin;
-- Test that UPDATE/DELETE with inherited target works with async_capable enabled
EXPLAIN (VERBOSE, COSTS OFF)
UPDATE async_pt SET c = c || c WHERE b = 0 RETURNING *;
QUERY PLAN
----------------------------------------------------------------------------------------------------------
Update on public.async_pt
Output: async_pt_1.a, async_pt_1.b, async_pt_1.c
Foreign Update on public.async_p1 async_pt_1
Foreign Update on public.async_p2 async_pt_2
Update on public.async_p3 async_pt_3
-> Append
-> Foreign Update on public.async_p1 async_pt_1
Remote SQL: UPDATE public.base_tbl1 SET c = (c || c) WHERE ((b = 0)) RETURNING a, b, c
-> Foreign Update on public.async_p2 async_pt_2
Remote SQL: UPDATE public.base_tbl2 SET c = (c || c) WHERE ((b = 0)) RETURNING a, b, c
-> Seq Scan on public.async_p3 async_pt_3
Output: (async_pt_3.c || async_pt_3.c), async_pt_3.tableoid, async_pt_3.ctid, NULL::record
Filter: (async_pt_3.b = 0)
(13 rows)
UPDATE async_pt SET c = c || c WHERE b = 0 RETURNING *;
a | b | c
------+---+----------
1000 | 0 | 00000000
2000 | 0 | 00000000
3000 | 0 | 00000000
(3 rows)
EXPLAIN (VERBOSE, COSTS OFF)
DELETE FROM async_pt WHERE b = 0 RETURNING *;
QUERY PLAN
------------------------------------------------------------------------------------------
Delete on public.async_pt
Output: async_pt_1.a, async_pt_1.b, async_pt_1.c
Foreign Delete on public.async_p1 async_pt_1
Foreign Delete on public.async_p2 async_pt_2
Delete on public.async_p3 async_pt_3
-> Append
-> Foreign Delete on public.async_p1 async_pt_1
Remote SQL: DELETE FROM public.base_tbl1 WHERE ((b = 0)) RETURNING a, b, c
-> Foreign Delete on public.async_p2 async_pt_2
Remote SQL: DELETE FROM public.base_tbl2 WHERE ((b = 0)) RETURNING a, b, c
-> Seq Scan on public.async_p3 async_pt_3
Output: async_pt_3.tableoid, async_pt_3.ctid
Filter: (async_pt_3.b = 0)
(13 rows)
DELETE FROM async_pt WHERE b = 0 RETURNING *;
a | b | c
------+---+----------
1000 | 0 | 00000000
2000 | 0 | 00000000
3000 | 0 | 00000000
(3 rows)
-- Check EXPLAIN ANALYZE for a query that scans empty partitions asynchronously
DELETE FROM async_p1;
DELETE FROM async_p2;

7
contrib/postgres_fdw/postgres_fdw.c
View File

@ -2530,6 +2530,13 @@ postgresPlanDirectModify(PlannerInfo *root,
rebuild_fdw_scan_tlist(fscan, returningList);
}
/*
* Finally, unset the async-capable flag if it is set, as we currently
* don't support asynchronous execution of direct modifications.
*/
if (fscan->scan.plan.async_capable)
fscan->scan.plan.async_capable = false;
table_close(rel, NoLock);
return true;
}

8
contrib/postgres_fdw/sql/postgres_fdw.sql
View File

@ -3237,6 +3237,14 @@ DROP TABLE base_tbl4;
RESET enable_mergejoin;
RESET enable_hashjoin;
-- Test that UPDATE/DELETE with inherited target works with async_capable enabled
EXPLAIN (VERBOSE, COSTS OFF)
UPDATE async_pt SET c = c || c WHERE b = 0 RETURNING *;
UPDATE async_pt SET c = c || c WHERE b = 0 RETURNING *;
EXPLAIN (VERBOSE, COSTS OFF)
DELETE FROM async_pt WHERE b = 0 RETURNING *;
DELETE FROM async_pt WHERE b = 0 RETURNING *;
-- Check EXPLAIN ANALYZE for a query that scans empty partitions asynchronously
DELETE FROM async_p1;
DELETE FROM async_p2;