From 33187ab5984fcbb4afc0999e478b3e965c4262ab Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 31 Jul 2024 20:54:59 -0400
Subject: [PATCH] Revert "Allow parallel workers to cope with a newly-created
session user ID."
This reverts commit 849326e49a5dd56941eb8fb4699130c301bff303.
Some buildfarm animals are failing with "cannot change
"client_encoding" during a parallel operation". It looks like
assign_client_encoding is unhappy at being asked to roll back a
client_encoding setting after a parallel worker encounters a
failure. There must be more to it though: why didn't I see this
during local testing? In any case, it's clear that moving the
RestoreGUCState() call is not as side-effect-free as I thought.
Given that the bug f5f30c22e intended to fix has gone unreported
for years, it's not something that's urgent to fix; I'm not
willing to risk messing with it further with only days to our
next release wrap.
---
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, 6 insertions(+), 43 deletions(-)
diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
index 8606c009dd9..2b8bc2f58dd 100644
--- a/src/backend/access/transam/parallel.c
+++ b/src/backend/access/transam/parallel.c
@@ -1414,6 +1414,10 @@ 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. */
@@ -1455,14 +1459,6 @@ 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 f25563fa5f0..f0f2e076552 100644
--- a/src/backend/commands/variable.c
+++ b/src/backend/commands/variable.c
@@ -577,16 +577,14 @@ 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,
- * or if restoring state in a parallel worker.
+ * As in check_transaction_read_only, allow it if not inside a transaction.
*/
bool
check_transaction_isolation(int *newval, void **extra, GucSource source)
{
int newXactIsoLevel = *newval;
- if (newXactIsoLevel != XactIsoLevel &&
- IsTransactionState() && !InitializingParallelWorker)
+ if (newXactIsoLevel != XactIsoLevel && IsTransactionState())
{
if (FirstSnapshotSet)
{
@@ -621,10 +619,6 @@ check_transaction_isolation(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 768b42c9293..d88353d496c 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -1219,21 +1219,3 @@ 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 debug_parallel_query = 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 e98c759bb25..80c914dc02b 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -462,12 +462,3 @@ 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 debug_parallel_query = 1;
-select current_setting('session_authorization');
-rollback;