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Commit4853630

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Allow parallel workers to cope with a newly-created session user ID.
Parallel workers failed after a sequence likeBEGIN;CREATE USER foo;SET SESSION AUTHORIZATION foo;because check_session_authorization could not see the uncommittedpg_authid row for "foo". This is because we ran RestoreGUCState()in a separate transaction using an ordinary just-created snapshot.The same disease afflicts any other GUC that requires catalog lookupsand isn't forgiving about the lookups failing.To fix, postpone RestoreGUCState() into the worker's main transactionafter we've set up a snapshot duplicating the leader's. This affectscheck_transaction_isolation and check_transaction_deferrable, whichthink they should only run during transaction start. Make themact like check_transaction_read_only, which already knows it shouldsilently accept the value when InitializingParallelWorker.Per bug #18545 from Andrey Rachitskiy. Back-patch to allsupported branches, because this has been wrong for awhile.Discussion:https://postgr.es/m/18545-feba138862f19aaa@postgresql.org
1 parent27146e7 commit4853630

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4 files changed

+43
-6
lines changed

4 files changed

+43
-6
lines changed

‎src/backend/access/transam/parallel.c‎

Lines changed: 8 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1402,10 +1402,6 @@ ParallelWorkerMain(Datum main_arg)
14021402
libraryspace=shm_toc_lookup(toc,PARALLEL_KEY_LIBRARY, false);
14031403
StartTransactionCommand();
14041404
RestoreLibraryState(libraryspace);
1405-
1406-
/* Restore GUC values from launching backend. */
1407-
gucspace=shm_toc_lookup(toc,PARALLEL_KEY_GUC, false);
1408-
RestoreGUCState(gucspace);
14091405
CommitTransactionCommand();
14101406

14111407
/* Crank up a transaction state appropriate to a parallel worker. */
@@ -1447,6 +1443,14 @@ ParallelWorkerMain(Datum main_arg)
14471443
*/
14481444
InvalidateSystemCaches();
14491445

1446+
/*
1447+
* Restore GUC values from launching backend. We can't do this earlier,
1448+
* because GUC check hooks that do catalog lookups need to see the same
1449+
* database state as the leader.
1450+
*/
1451+
gucspace=shm_toc_lookup(toc,PARALLEL_KEY_GUC, false);
1452+
RestoreGUCState(gucspace);
1453+
14501454
/*
14511455
* Restore current role id. Skip verifying whether session user is
14521456
* allowed to become this role and blindly restore the leader's state for

‎src/backend/commands/variable.c‎

Lines changed: 8 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -519,14 +519,16 @@ check_transaction_read_only(bool *newval, void **extra, GucSource source)
519519
* We allow idempotent changes at any time, but otherwise this can only be
520520
* changed in a toplevel transaction that has not yet taken a snapshot.
521521
*
522-
* As in check_transaction_read_only, allow it if not inside a transaction.
522+
* As in check_transaction_read_only, allow it if not inside a transaction,
523+
* or if restoring state in a parallel worker.
523524
*/
524525
bool
525526
check_XactIsoLevel(int*newval,void**extra,GucSourcesource)
526527
{
527528
intnewXactIsoLevel=*newval;
528529

529-
if (newXactIsoLevel!=XactIsoLevel&&IsTransactionState())
530+
if (newXactIsoLevel!=XactIsoLevel&&
531+
IsTransactionState()&& !InitializingParallelWorker)
530532
{
531533
if (FirstSnapshotSet)
532534
{
@@ -561,6 +563,10 @@ check_XactIsoLevel(int *newval, void **extra, GucSource source)
561563
bool
562564
check_transaction_deferrable(bool*newval,void**extra,GucSourcesource)
563565
{
566+
/* Just accept the value when restoring state in a parallel worker */
567+
if (InitializingParallelWorker)
568+
return true;
569+
564570
if (IsSubTransaction())
565571
{
566572
GUC_check_errcode(ERRCODE_ACTIVE_SQL_TRANSACTION);

‎src/test/regress/expected/select_parallel.out‎

Lines changed: 18 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1219,3 +1219,21 @@ SELECT 1 FROM tenk1_vw_sec
12191219
(9 rows)
12201220

12211221
rollback;
1222+
-- test that a newly-created session role propagates to workers.
1223+
begin;
1224+
create role regress_parallel_worker;
1225+
set session authorization regress_parallel_worker;
1226+
select current_setting('session_authorization');
1227+
current_setting
1228+
-------------------------
1229+
regress_parallel_worker
1230+
(1 row)
1231+
1232+
set force_parallel_mode = 1;
1233+
select current_setting('session_authorization');
1234+
current_setting
1235+
-------------------------
1236+
regress_parallel_worker
1237+
(1 row)
1238+
1239+
rollback;

‎src/test/regress/sql/select_parallel.sql‎

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -462,3 +462,12 @@ SELECT 1 FROM tenk1_vw_sec
462462
WHERE (SELECTsum(f1)FROM int4_tblWHERE f1< unique1)<100;
463463

464464
rollback;
465+
466+
-- test that a newly-created session role propagates to workers.
467+
begin;
468+
create role regress_parallel_worker;
469+
set session authorization regress_parallel_worker;
470+
select current_setting('session_authorization');
471+
set force_parallel_mode=1;
472+
select current_setting('session_authorization');
473+
rollback;

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