Commit2370582

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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
`@@ -340,6 +340,11 @@ standard_planner(Query parse, const char query_string, int cursorOptions,`
`340`	`340`	`* we want to allow parallel inserts in general; updates and deletes have`
`341`	`341`	`* additional problems especially around combo CIDs.)`
`342`	`342`	`*`
	`343`	`+ * We don't try to use parallel mode unless interruptible. The leader`
	`344`	`+ * expects ProcessInterrupts() calls to reach HandleParallelMessages().`
	`345`	`+ * Even if we called HandleParallelMessages() another way, starting a`
	`346`	`+ * parallel worker is too delay-prone to be prudent when uncancellable.`
	`347`	`+ *`
`343`	`348`	`* For now, we don't try to use parallel mode if we're running inside a`
`344`	`349`	`* parallel worker. We might eventually be able to relax this`
`345`	`350`	`* restriction, but for now it seems best not to have parallel workers`
`@@ -350,6 +355,7 @@ standard_planner(Query parse, const char query_string, int cursorOptions,`
`350`	`355`	`parse->commandType==CMD_SELECT&&`
`351`	`356`	`!parse->hasModifyingCTE&&`
`352`	`357`	`max_parallel_workers_per_gather>0&&`
	`358`	`+INTERRUPTS_CAN_BE_PROCESSED()&&`
`353`	`359`	`!IsParallelWorker())`
`354`	`360`	`{`
`355`	`361`	`/* 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
`@@ -1327,3 +1327,27 @@ reset debug_parallel_query;`
`1327`	`1327`	`drop function set_and_report_role();`
`1328`	`1328`	`drop function set_role_and_error(int);`
`1329`	`1329`	`drop role regress_parallel_worker;`
	`1330`	`+-- don't freeze in ParallelFinish while holding an LWLock`
	`1331`	`+BEGIN;`
	`1332`	`+CREATE FUNCTION my_cmp (int4, int4)`
	`1333`	`+RETURNS int LANGUAGE sql AS`
	`1334`	`+$$`
	`1335`	`+SELECT`
	`1336`	`+CASE WHEN $1 < $2 THEN -1`
	`1337`	`+WHEN $1 > $2 THEN 1`
	`1338`	`+ELSE 0`
	`1339`	`+END;`
	`1340`	`+$$;`
	`1341`	`+CREATE TABLE parallel_hang (i int4);`
	`1342`	`+INSERT INTO parallel_hang`
	`1343`	`+(SELECT * FROM generate_series(1, 400) gs);`
	`1344`	`+CREATE OPERATOR CLASS int4_custom_ops FOR TYPE int4 USING btree AS`
	`1345`	`+OPERATOR 1 < (int4, int4), OPERATOR 2 <= (int4, int4),`
	`1346`	`+OPERATOR 3 = (int4, int4), OPERATOR 4 >= (int4, int4),`
	`1347`	`+OPERATOR 5 > (int4, int4), FUNCTION 1 my_cmp(int4, int4);`
	`1348`	`+CREATE UNIQUE INDEX parallel_hang_idx`
	`1349`	`+ON parallel_hang`
	`1350`	`+USING btree (i int4_custom_ops);`
	`1351`	`+SET debug_parallel_query = on;`
	`1352`	`+DELETE FROM parallel_hang WHERE 380 <= i AND i <= 420;`
	`1353`	`+ROLLBACK;`

Lines changed: 31 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -519,3 +519,34 @@ reset debug_parallel_query;`
`519`	`519`	`dropfunction set_and_report_role();`
`520`	`520`	`dropfunction set_role_and_error(int);`
`521`	`521`	`drop role regress_parallel_worker;`
	`522`	`+`
	`523`	`+-- don't freeze in ParallelFinish while holding an LWLock`
	`524`	`+BEGIN;`
	`525`	`+`
	`526`	`+CREATEFUNCTIONmy_cmp (int4, int4)`
	`527`	`+RETURNSint LANGUAGE sqlAS`
	`528`	`+$$`
	`529`	`+SELECT`
	`530`	`+CASE WHEN $1< $2 THEN-1`
	`531`	`+WHEN $1> $2 THEN1`
	`532`	`+ELSE0`
	`533`	`+END;`
	`534`	`+$$;`
	`535`	`+`
	`536`	`+CREATETABLEparallel_hang (i int4);`
	`537`	`+INSERT INTO parallel_hang`
	`538`	`+(SELECT*FROM generate_series(1,400) gs);`
	`539`	`+`
	`540`	`+CREATEOPERATOR CLASSint4_custom_ops FOR TYPE int4 USING btreeAS`
	`541`	`+OPERATOR1< (int4, int4), OPERATOR2<= (int4, int4),`
	`542`	`+OPERATOR3= (int4, int4), OPERATOR4>= (int4, int4),`
	`543`	`+OPERATOR5> (int4, int4), FUNCTION1 my_cmp(int4, int4);`
	`544`	`+`
	`545`	`+CREATEUNIQUE INDEXparallel_hang_idx`
	`546`	`+ON parallel_hang`
	`547`	`+USING btree (i int4_custom_ops);`
	`548`	`+`
	`549`	`+SET debug_parallel_query=on;`
	`550`	`+DELETEFROM parallel_hangWHERE380<= iAND i<=420;`
	`551`	`+`
	`552`	`+ROLLBACK;`

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