From: Amit Kapila Date: Sat, 18 Jul 2026 02:23:13 +0000 (+0530) Subject: Revert "Reject concurrent sequence refreshes". X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=fd27c7e64fe0d5d514ee5fa97250327ce33756fa;p=thirdparty%2Fpostgresql.git Revert "Reject concurrent sequence refreshes". This reverts commit f38afa4abb04e85530c94b88daf11c089375daca. That commit fixed a race that could leave stale sequence values on the subscriber after 'ALTER SUBSCRIPTION ... REFRESH SEQUENCES'. It did so by raising an ERROR during 'ALTER SUBSCRIPTION ... REFRESH SEQUENCES' whenever a sequence synchronization worker was already running for the subscription. That approach caused intermittent buildfarm failures, because the existing tests did not ensure the sequencesync worker had stopped before executing 'ALTER SUBSCRIPTION ... REFRESH SEQUENCES'. While discussing how to fix the tests, we concluded that blocking the command while a sequencesync worker is running is inconvenient for users. So we will fix the original race differently in a follow-up commit. Reported-by: Tom Lane Author: Amit Kapila Backpatch-through: 19 Discussion: https://postgr.es/m/3614163.1784163070@sss.pgh.pa.us Discussion: https://postgr.es/m/20260710045217.f0.noahmisch@microsoft.com --- diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c index 94b163cccc9..ee06a726f42 100644 --- a/src/backend/commands/subscriptioncmds.c +++ b/src/backend/commands/subscriptioncmds.c @@ -1304,33 +1304,6 @@ AlterSubscription_refresh_seq(Subscription *sub) WalReceiverConn *wrconn; bool must_use_password; - /* - * Disallow a concurrent REFRESH SEQUENCES while a sequence sync worker - * for this subscription is still running. This avoids a race where the - * publisher's sequence advances after the current worker has fetched its - * value but before it marks the sequence READY. A user may then issue - * another REFRESH SEQUENCES to synchronize the updated value. Since the - * affected sequences are already in the INIT state, the running worker - * has no indication that a new synchronization has been requested. It - * would then apply the stale value it already fetched and mark the - * sequence READY, causing the new synchronization request to be lost and - * preventing the updated publisher values from being synchronized. - */ - LWLockAcquire(LogicalRepWorkerLock, LW_SHARED); - if (logicalrep_worker_find(WORKERTYPE_SEQUENCESYNC, sub->oid, InvalidOid, - true)) - { - LWLockRelease(LogicalRepWorkerLock); - ereport(ERROR, - errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), - /* translator: %s is an SQL ALTER command */ - errmsg("cannot execute %s while a sequence synchronization worker is running", - "ALTER SUBSCRIPTION ... REFRESH SEQUENCES"), - errhint("Try again after the current synchronization completes.")); - } - - LWLockRelease(LogicalRepWorkerLock); - /* Load the library providing us libpq calls. */ load_file("libpqwalreceiver", false); diff --git a/src/test/subscription/t/036_sequences.pl b/src/test/subscription/t/036_sequences.pl index b3b3b20f82b..77ac9386cd8 100644 --- a/src/test/subscription/t/036_sequences.pl +++ b/src/test/subscription/t/036_sequences.pl @@ -286,10 +286,6 @@ $node_publisher->safe_psql( CREATE SEQUENCE regress_s4 START 10 INCREMENT 2; )); -# Wait for the missing sequence added to be synced -$node_subscriber->poll_query_until('postgres', $synced_query) - or die "Timed out while waiting for subscriber to synchronize data"; - ########## # Ensure that insufficient privileges on the publisher for a sequence # are reported correctly as a permission issue, not as a missing sequence.