Commitac04aa8

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Don't enter parallel mode when holding interrupts.

Doing so caused the leader to hang in wait_event=ParallelFinish, whichrequired an immediate shutdown to resolve. Back-patch to v12 (allsupported versions).Francesco DegrassiDiscussion:https://postgr.es/m/CAC-SaSzHUKT=vZJ8MPxYdC_URPfax+yoA1hKTcF4ROz_Q6z0_Q@mail.gmail.com

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Original file line number	Diff line number	Diff line change
`@@ -342,6 +342,11 @@ standard_planner(Query parse, const char query_string, int cursorOptions,`
`342`	`342`	`* we want to allow parallel inserts in general; updates and deletes have`
`343`	`343`	`* additional problems especially around combo CIDs.)`
`344`	`344`	`*`
	`345`	`+ * We don't try to use parallel mode unless interruptible. The leader`
	`346`	`+ * expects ProcessInterrupts() calls to reach HandleParallelMessages().`
	`347`	`+ * Even if we called HandleParallelMessages() another way, starting a`
	`348`	`+ * parallel worker is too delay-prone to be prudent when uncancellable.`
	`349`	`+ *`
`345`	`350`	`* For now, we don't try to use parallel mode if we're running inside a`
`346`	`351`	`* parallel worker. We might eventually be able to relax this`
`347`	`352`	`* restriction, but for now it seems best not to have parallel workers`
`@@ -352,6 +357,7 @@ standard_planner(Query parse, const char query_string, int cursorOptions,`
`352`	`357`	`parse->commandType==CMD_SELECT&&`
`353`	`358`	`!parse->hasModifyingCTE&&`
`354`	`359`	`max_parallel_workers_per_gather>0&&`
	`360`	`+INTERRUPTS_CAN_BE_PROCESSED()&&`
`355`	`361`	`!IsParallelWorker())`
`356`	`362`	`{`
`357`	`363`	`/* all the cheap tests pass, so scan the query tree */`

Lines changed: 24 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -1386,3 +1386,27 @@ reset debug_parallel_query;`
`1386`	`1386`	`drop function set_and_report_role();`
`1387`	`1387`	`drop function set_role_and_error(int);`
`1388`	`1388`	`drop role regress_parallel_worker;`
	`1389`	`+-- don't freeze in ParallelFinish while holding an LWLock`
	`1390`	`+BEGIN;`
	`1391`	`+CREATE FUNCTION my_cmp (int4, int4)`
	`1392`	`+RETURNS int LANGUAGE sql AS`
	`1393`	`+$$`
	`1394`	`+SELECT`
	`1395`	`+CASE WHEN $1 < $2 THEN -1`
	`1396`	`+WHEN $1 > $2 THEN 1`
	`1397`	`+ELSE 0`
	`1398`	`+END;`
	`1399`	`+$$;`
	`1400`	`+CREATE TABLE parallel_hang (i int4);`
	`1401`	`+INSERT INTO parallel_hang`
	`1402`	`+(SELECT * FROM generate_series(1, 400) gs);`
	`1403`	`+CREATE OPERATOR CLASS int4_custom_ops FOR TYPE int4 USING btree AS`
	`1404`	`+OPERATOR 1 < (int4, int4), OPERATOR 2 <= (int4, int4),`
	`1405`	`+OPERATOR 3 = (int4, int4), OPERATOR 4 >= (int4, int4),`
	`1406`	`+OPERATOR 5 > (int4, int4), FUNCTION 1 my_cmp(int4, int4);`
	`1407`	`+CREATE UNIQUE INDEX parallel_hang_idx`
	`1408`	`+ON parallel_hang`
	`1409`	`+USING btree (i int4_custom_ops);`
	`1410`	`+SET debug_parallel_query = on;`
	`1411`	`+DELETE FROM parallel_hang WHERE 380 <= i AND i <= 420;`
	`1412`	`+ROLLBACK;`

Lines changed: 31 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -543,3 +543,34 @@ reset debug_parallel_query;`
`543`	`543`	`dropfunction set_and_report_role();`
`544`	`544`	`dropfunction set_role_and_error(int);`
`545`	`545`	`drop role regress_parallel_worker;`
	`546`	`+`
	`547`	`+-- don't freeze in ParallelFinish while holding an LWLock`
	`548`	`+BEGIN;`
	`549`	`+`
	`550`	`+CREATEFUNCTIONmy_cmp (int4, int4)`
	`551`	`+RETURNSint LANGUAGE sqlAS`
	`552`	`+$$`
	`553`	`+SELECT`
	`554`	`+CASE WHEN $1< $2 THEN-1`
	`555`	`+WHEN $1> $2 THEN1`
	`556`	`+ELSE0`
	`557`	`+END;`
	`558`	`+$$;`
	`559`	`+`
	`560`	`+CREATETABLEparallel_hang (i int4);`
	`561`	`+INSERT INTO parallel_hang`
	`562`	`+(SELECT*FROM generate_series(1,400) gs);`
	`563`	`+`
	`564`	`+CREATEOPERATOR CLASSint4_custom_ops FOR TYPE int4 USING btreeAS`
	`565`	`+OPERATOR1< (int4, int4), OPERATOR2<= (int4, int4),`
	`566`	`+OPERATOR3= (int4, int4), OPERATOR4>= (int4, int4),`
	`567`	`+OPERATOR5> (int4, int4), FUNCTION1 my_cmp(int4, int4);`
	`568`	`+`
	`569`	`+CREATEUNIQUE INDEXparallel_hang_idx`
	`570`	`+ON parallel_hang`
	`571`	`+USING btree (i int4_custom_ops);`
	`572`	`+`
	`573`	`+SET debug_parallel_query=on;`
	`574`	`+DELETEFROM parallel_hangWHERE380<= iAND i<=420;`
	`575`	`+`
	`576`	`+ROLLBACK;`

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