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Etsuro Fujita
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Prevent asynchronous execution of direct foreign-table modifications.
Commits 27e1f14 and 86dc900, 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
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‎contrib/postgres_fdw/expected/postgres_fdw.out

+55
Original file line numberDiff line numberDiff line change
@@ -10154,6 +10154,61 @@ DROP TABLE base_tbl3;
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DROP TABLE base_tbl4;
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RESET enable_mergejoin;
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RESET enable_hashjoin;
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-- Test that UPDATE/DELETE with inherited target works with async_capable enabled
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EXPLAIN (VERBOSE, COSTS OFF)
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UPDATE async_pt SET c = c || c WHERE b = 0 RETURNING *;
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QUERY PLAN
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----------------------------------------------------------------------------------------------------------
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Update on public.async_pt
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Output: async_pt_1.a, async_pt_1.b, async_pt_1.c
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Foreign Update on public.async_p1 async_pt_1
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Foreign Update on public.async_p2 async_pt_2
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Update on public.async_p3 async_pt_3
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-> Append
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-> Foreign Update on public.async_p1 async_pt_1
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Remote SQL: UPDATE public.base_tbl1 SET c = (c || c) WHERE ((b = 0)) RETURNING a, b, c
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-> Foreign Update on public.async_p2 async_pt_2
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Remote SQL: UPDATE public.base_tbl2 SET c = (c || c) WHERE ((b = 0)) RETURNING a, b, c
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-> Seq Scan on public.async_p3 async_pt_3
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Output: (async_pt_3.c || async_pt_3.c), async_pt_3.tableoid, async_pt_3.ctid, NULL::record
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Filter: (async_pt_3.b = 0)
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(13 rows)
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UPDATE async_pt SET c = c || c WHERE b = 0 RETURNING *;
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a | b | c
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------+---+----------
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1000 | 0 | 00000000
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2000 | 0 | 00000000
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3000 | 0 | 00000000
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(3 rows)
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EXPLAIN (VERBOSE, COSTS OFF)
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DELETE FROM async_pt WHERE b = 0 RETURNING *;
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QUERY PLAN
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------------------------------------------------------------------------------------------
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Delete on public.async_pt
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Output: async_pt_1.a, async_pt_1.b, async_pt_1.c
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Foreign Delete on public.async_p1 async_pt_1
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Foreign Delete on public.async_p2 async_pt_2
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Delete on public.async_p3 async_pt_3
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-> Append
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-> Foreign Delete on public.async_p1 async_pt_1
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Remote SQL: DELETE FROM public.base_tbl1 WHERE ((b = 0)) RETURNING a, b, c
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-> Foreign Delete on public.async_p2 async_pt_2
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Remote SQL: DELETE FROM public.base_tbl2 WHERE ((b = 0)) RETURNING a, b, c
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-> Seq Scan on public.async_p3 async_pt_3
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Output: async_pt_3.tableoid, async_pt_3.ctid
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Filter: (async_pt_3.b = 0)
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(13 rows)
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DELETE FROM async_pt WHERE b = 0 RETURNING *;
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a | b | c
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------+---+----------
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1000 | 0 | 00000000
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2000 | 0 | 00000000
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3000 | 0 | 00000000
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(3 rows)
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-- Check EXPLAIN ANALYZE for a query that scans empty partitions asynchronously
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DELETE FROM async_p1;
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DELETE FROM async_p2;

‎contrib/postgres_fdw/postgres_fdw.c

+7
Original file line numberDiff line numberDiff line change
@@ -2530,6 +2530,13 @@ postgresPlanDirectModify(PlannerInfo *root,
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rebuild_fdw_scan_tlist(fscan, returningList);
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}
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/*
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* Finally, unset the async-capable flag if it is set, as we currently
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* don't support asynchronous execution of direct modifications.
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*/
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if (fscan->scan.plan.async_capable)
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fscan->scan.plan.async_capable = false;
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table_close(rel, NoLock);
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return true;
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}

‎contrib/postgres_fdw/sql/postgres_fdw.sql

+8
Original file line numberDiff line numberDiff line change
@@ -3237,6 +3237,14 @@ DROP TABLE base_tbl4;
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RESET enable_mergejoin;
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RESET enable_hashjoin;
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-- Test that UPDATE/DELETE with inherited target works with async_capable enabled
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EXPLAIN (VERBOSE, COSTS OFF)
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UPDATE async_pt SET c = c || c WHERE b = 0 RETURNING *;
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UPDATE async_pt SET c = c || c WHERE b = 0 RETURNING *;
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EXPLAIN (VERBOSE, COSTS OFF)
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DELETE FROM async_pt WHERE b = 0 RETURNING *;
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DELETE FROM async_pt WHERE b = 0 RETURNING *;
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-- Check EXPLAIN ANALYZE for a query that scans empty partitions asynchronously
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DELETE FROM async_p1;
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DELETE FROM async_p2;

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