Commit916b8ae

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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
`@@ -332,6 +332,11 @@ standard_planner(Query parse, const char query_string, int cursorOptions,`
`332`	`332`	`* if we want to allow parallel inserts in general; updates and deletes`
`333`	`333`	`* have additional problems especially around combo CIDs.)`
`334`	`334`	`*`
	`335`	`+ * We don't try to use parallel mode unless interruptible. The leader`
	`336`	`+ * expects ProcessInterrupts() calls to reach HandleParallelMessages().`
	`337`	`+ * Even if we called HandleParallelMessages() another way, starting a`
	`338`	`+ * parallel worker is too delay-prone to be prudent when uncancellable.`
	`339`	`+ *`
`335`	`340`	`* For now, we don't try to use parallel mode if we're running inside a`
`336`	`341`	`* parallel worker. We might eventually be able to relax this`
`337`	`342`	`* restriction, but for now it seems best not to have parallel workers`
`@@ -342,6 +347,7 @@ standard_planner(Query parse, const char query_string, int cursorOptions,`
`342`	`347`	`parse->commandType==CMD_SELECT&&`
`343`	`348`	`!parse->hasModifyingCTE&&`
`344`	`349`	`max_parallel_workers_per_gather>0&&`
	`350`	`+INTERRUPTS_CAN_BE_PROCESSED()&&`
`345`	`351`	`!IsParallelWorker())`
`346`	`352`	`{`
`347`	`353`	`/* 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
`@@ -1254,3 +1254,27 @@ reset force_parallel_mode;`
`1254`	`1254`	`drop function set_and_report_role();`
`1255`	`1255`	`drop function set_role_and_error(int);`
`1256`	`1256`	`drop role regress_parallel_worker;`
	`1257`	`+-- don't freeze in ParallelFinish while holding an LWLock`
	`1258`	`+BEGIN;`
	`1259`	`+CREATE FUNCTION my_cmp (int4, int4)`
	`1260`	`+RETURNS int LANGUAGE sql AS`
	`1261`	`+$$`
	`1262`	`+SELECT`
	`1263`	`+CASE WHEN $1 < $2 THEN -1`
	`1264`	`+WHEN $1 > $2 THEN 1`
	`1265`	`+ELSE 0`
	`1266`	`+END;`
	`1267`	`+$$;`
	`1268`	`+CREATE TABLE parallel_hang (i int4);`
	`1269`	`+INSERT INTO parallel_hang`
	`1270`	`+(SELECT * FROM generate_series(1, 400) gs);`
	`1271`	`+CREATE OPERATOR CLASS int4_custom_ops FOR TYPE int4 USING btree AS`
	`1272`	`+OPERATOR 1 < (int4, int4), OPERATOR 2 <= (int4, int4),`
	`1273`	`+OPERATOR 3 = (int4, int4), OPERATOR 4 >= (int4, int4),`
	`1274`	`+OPERATOR 5 > (int4, int4), FUNCTION 1 my_cmp(int4, int4);`
	`1275`	`+CREATE UNIQUE INDEX parallel_hang_idx`
	`1276`	`+ON parallel_hang`
	`1277`	`+USING btree (i int4_custom_ops);`
	`1278`	`+SET force_parallel_mode = on;`
	`1279`	`+DELETE FROM parallel_hang WHERE 380 <= i AND i <= 420;`
	`1280`	`+ROLLBACK;`

Lines changed: 31 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -487,3 +487,34 @@ reset force_parallel_mode;`
`487`	`487`	`dropfunction set_and_report_role();`
`488`	`488`	`dropfunction set_role_and_error(int);`
`489`	`489`	`drop role regress_parallel_worker;`
	`490`	`+`
	`491`	`+-- don't freeze in ParallelFinish while holding an LWLock`
	`492`	`+BEGIN;`
	`493`	`+`
	`494`	`+CREATEFUNCTIONmy_cmp (int4, int4)`
	`495`	`+RETURNSint LANGUAGE sqlAS`
	`496`	`+$$`
	`497`	`+SELECT`
	`498`	`+CASE WHEN $1< $2 THEN-1`
	`499`	`+WHEN $1> $2 THEN1`
	`500`	`+ELSE0`
	`501`	`+END;`
	`502`	`+$$;`
	`503`	`+`
	`504`	`+CREATETABLEparallel_hang (i int4);`
	`505`	`+INSERT INTO parallel_hang`
	`506`	`+(SELECT*FROM generate_series(1,400) gs);`
	`507`	`+`
	`508`	`+CREATEOPERATOR CLASSint4_custom_ops FOR TYPE int4 USING btreeAS`
	`509`	`+OPERATOR1< (int4, int4), OPERATOR2<= (int4, int4),`
	`510`	`+OPERATOR3= (int4, int4), OPERATOR4>= (int4, int4),`
	`511`	`+OPERATOR5> (int4, int4), FUNCTION1 my_cmp(int4, int4);`
	`512`	`+`
	`513`	`+CREATEUNIQUE INDEXparallel_hang_idx`
	`514`	`+ON parallel_hang`
	`515`	`+USING btree (i int4_custom_ops);`
	`516`	`+`
	`517`	`+SET force_parallel_mode=on;`
	`518`	`+DELETEFROM parallel_hangWHERE380<= iAND i<=420;`
	`519`	`+`
	`520`	`+ROLLBACK;`

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