From 507b72bd9f7de95a224ae5af8797f42bfce1ed9c Mon Sep 17 00:00:00 2001 From: Noah Misch Date: Tue, 17 Sep 2024 19:53:11 -0700 Subject: [PATCH] Don't enter parallel mode when holding interrupts. Doing so caused the leader to hang in wait_event=ParallelFinish, which required an immediate shutdown to resolve. Back-patch to v12 (all supported versions). Francesco Degrassi Discussion: https://postgr.es/m/CAC-SaSzHUKT=vZJ8MPxYdC_URPfax+yoA1hKTcF4ROz_Q6z0_Q@mail.gmail.com --- src/backend/optimizer/plan/planner.c | 6 ++++ src/test/regress/expected/select_parallel.out | 24 ++++++++++++++ src/test/regress/sql/select_parallel.sql | 31 +++++++++++++++++++ 3 files changed, 61 insertions(+) diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c index 65a9b0d802a..f7539fed6fb 100644 --- a/src/backend/optimizer/plan/planner.c +++ b/src/backend/optimizer/plan/planner.c @@ -331,6 +331,11 @@ standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams) * general; updates and deletes have additional problems especially around * combo CIDs.) * + * We don't try to use parallel mode unless interruptible. The leader + * expects ProcessInterrupts() calls to reach HandleParallelMessages(). + * Even if we called HandleParallelMessages() another way, starting a + * parallel worker is too delay-prone to be prudent when uncancellable. + * * For now, we don't try to use parallel mode if we're running inside a * parallel worker. We might eventually be able to relax this * restriction, but for now it seems best not to have parallel workers @@ -341,6 +346,7 @@ standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams) parse->commandType == CMD_SELECT && !parse->hasModifyingCTE && max_parallel_workers_per_gather > 0 && + INTERRUPTS_CAN_BE_PROCESSED() && !IsParallelWorker()) { /* all the cheap tests pass, so scan the query tree */ diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out index c5943e55a0e..7df008c3c3f 100644 --- a/src/test/regress/expected/select_parallel.out +++ b/src/test/regress/expected/select_parallel.out @@ -1207,3 +1207,27 @@ reset force_parallel_mode; drop function set_and_report_role(); drop function set_role_and_error(int); drop role regress_parallel_worker; +-- don't freeze in ParallelFinish while holding an LWLock +BEGIN; +CREATE FUNCTION my_cmp (int4, int4) +RETURNS int LANGUAGE sql AS +$$ + SELECT + CASE WHEN $1 < $2 THEN -1 + WHEN $1 > $2 THEN 1 + ELSE 0 + END; +$$; +CREATE TABLE parallel_hang (i int4); +INSERT INTO parallel_hang + (SELECT * FROM generate_series(1, 400) gs); +CREATE OPERATOR CLASS int4_custom_ops FOR TYPE int4 USING btree AS + OPERATOR 1 < (int4, int4), OPERATOR 2 <= (int4, int4), + OPERATOR 3 = (int4, int4), OPERATOR 4 >= (int4, int4), + OPERATOR 5 > (int4, int4), FUNCTION 1 my_cmp(int4, int4); +CREATE UNIQUE INDEX parallel_hang_idx + ON parallel_hang + USING btree (i int4_custom_ops); +SET force_parallel_mode = on; +DELETE FROM parallel_hang WHERE 380 <= i AND i <= 420; +ROLLBACK; diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql index a31770cfc34..2f7f7563d21 100644 --- a/src/test/regress/sql/select_parallel.sql +++ b/src/test/regress/sql/select_parallel.sql @@ -477,3 +477,34 @@ reset force_parallel_mode; drop function set_and_report_role(); drop function set_role_and_error(int); drop role regress_parallel_worker; + +-- don't freeze in ParallelFinish while holding an LWLock +BEGIN; + +CREATE FUNCTION my_cmp (int4, int4) +RETURNS int LANGUAGE sql AS +$$ + SELECT + CASE WHEN $1 < $2 THEN -1 + WHEN $1 > $2 THEN 1 + ELSE 0 + END; +$$; + +CREATE TABLE parallel_hang (i int4); +INSERT INTO parallel_hang + (SELECT * FROM generate_series(1, 400) gs); + +CREATE OPERATOR CLASS int4_custom_ops FOR TYPE int4 USING btree AS + OPERATOR 1 < (int4, int4), OPERATOR 2 <= (int4, int4), + OPERATOR 3 = (int4, int4), OPERATOR 4 >= (int4, int4), + OPERATOR 5 > (int4, int4), FUNCTION 1 my_cmp(int4, int4); + +CREATE UNIQUE INDEX parallel_hang_idx + ON parallel_hang + USING btree (i int4_custom_ops); + +SET force_parallel_mode = on; +DELETE FROM parallel_hang WHERE 380 <= i AND i <= 420; + +ROLLBACK; -- 2.39.5