From 97380d4803d1f9188a1436c6fe7ecd7db285c55c Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 31 Jul 2024 18:54:10 -0400 Subject: [PATCH] Allow parallel workers to cope with a newly-created session user ID. Parallel workers failed after a sequence like BEGIN; CREATE USER foo; SET SESSION AUTHORIZATION foo; because check_session_authorization could not see the uncommitted pg_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 lookups and isn't forgiving about the lookups failing. To fix, postpone RestoreGUCState() into the worker's main transaction after we've set up a snapshot duplicating the leader's. This affects check_transaction_isolation and check_transaction_deferrable, which think they should only run during transaction start. Make them act like check_transaction_read_only, which already knows it should silently accept the value when InitializingParallelWorker. Per bug #18545 from Andrey Rachitskiy. Back-patch to all supported branches, because this has been wrong for awhile. Discussion: https://postgr.es/m/18545-feba138862f19aaa@postgresql.org --- src/backend/access/transam/parallel.c | 12 ++++++++---- src/backend/commands/variable.c | 10 ++++++++-- src/test/regress/expected/select_parallel.out | 18 ++++++++++++++++++ src/test/regress/sql/select_parallel.sql | 9 +++++++++ 4 files changed, 43 insertions(+), 6 deletions(-) diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c index 8ce95ab190b..7d8966cc206 100644 --- a/src/backend/access/transam/parallel.c +++ b/src/backend/access/transam/parallel.c @@ -1402,10 +1402,6 @@ ParallelWorkerMain(Datum main_arg) libraryspace = shm_toc_lookup(toc, PARALLEL_KEY_LIBRARY, false); StartTransactionCommand(); RestoreLibraryState(libraryspace); - - /* Restore GUC values from launching backend. */ - gucspace = shm_toc_lookup(toc, PARALLEL_KEY_GUC, false); - RestoreGUCState(gucspace); CommitTransactionCommand(); /* Crank up a transaction state appropriate to a parallel worker. */ @@ -1447,6 +1443,14 @@ ParallelWorkerMain(Datum main_arg) */ InvalidateSystemCaches(); + /* + * Restore GUC values from launching backend. We can't do this earlier, + * because GUC check hooks that do catalog lookups need to see the same + * database state as the leader. + */ + gucspace = shm_toc_lookup(toc, PARALLEL_KEY_GUC, false); + RestoreGUCState(gucspace); + /* * Restore current role id. Skip verifying whether session user is * allowed to become this role and blindly restore the leader's state for diff --git a/src/backend/commands/variable.c b/src/backend/commands/variable.c index 0c85679420c..a10ea7da0b4 100644 --- a/src/backend/commands/variable.c +++ b/src/backend/commands/variable.c @@ -519,14 +519,16 @@ check_transaction_read_only(bool *newval, void **extra, GucSource source) * We allow idempotent changes at any time, but otherwise this can only be * changed in a toplevel transaction that has not yet taken a snapshot. * - * As in check_transaction_read_only, allow it if not inside a transaction. + * As in check_transaction_read_only, allow it if not inside a transaction, + * or if restoring state in a parallel worker. */ bool check_XactIsoLevel(int *newval, void **extra, GucSource source) { int newXactIsoLevel = *newval; - if (newXactIsoLevel != XactIsoLevel && IsTransactionState()) + if (newXactIsoLevel != XactIsoLevel && + IsTransactionState() && !InitializingParallelWorker) { if (FirstSnapshotSet) { @@ -561,6 +563,10 @@ check_XactIsoLevel(int *newval, void **extra, GucSource source) bool check_transaction_deferrable(bool *newval, void **extra, GucSource source) { + /* Just accept the value when restoring state in a parallel worker */ + if (InitializingParallelWorker) + return true; + if (IsSubTransaction()) { GUC_check_errcode(ERRCODE_ACTIVE_SQL_TRANSACTION); diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out index 91f74fe47a3..3c6887fcb97 100644 --- a/src/test/regress/expected/select_parallel.out +++ b/src/test/regress/expected/select_parallel.out @@ -1219,3 +1219,21 @@ SELECT 1 FROM tenk1_vw_sec (9 rows) rollback; +-- test that a newly-created session role propagates to workers. +begin; +create role regress_parallel_worker; +set session authorization regress_parallel_worker; +select current_setting('session_authorization'); + current_setting +------------------------- + regress_parallel_worker +(1 row) + +set force_parallel_mode = 1; +select current_setting('session_authorization'); + current_setting +------------------------- + regress_parallel_worker +(1 row) + +rollback; diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql index 62fb68c7a04..11d861584ef 100644 --- a/src/test/regress/sql/select_parallel.sql +++ b/src/test/regress/sql/select_parallel.sql @@ -462,3 +462,12 @@ SELECT 1 FROM tenk1_vw_sec WHERE (SELECT sum(f1) FROM int4_tbl WHERE f1 < unique1) < 100; rollback; + +-- test that a newly-created session role propagates to workers. +begin; +create role regress_parallel_worker; +set session authorization regress_parallel_worker; +select current_setting('session_authorization'); +set force_parallel_mode = 1; +select current_setting('session_authorization'); +rollback; -- 2.39.5