Re: Perform streaming logical transactions by background workers and parallel apply - Mailing list pgsql-hackers

On Wed, Dec 21, 2022 at 11:02 AM houzj.fnst@fujitsu.com
<houzj.fnst@fujitsu.com> wrote:
>
>
> Attach the new patch set which also includes some
> cosmetic comment changes.
>

I noticed one problem with the recent change in the patch.

+ * The fileset state should become FS_SERIALIZE_DONE once we have waited
+ * for a lock in the FS_SERIALIZE_IN_PROGRESS state, so we get the state
+ * again and recheck it later.
+ */
+ if (fileset_state == FS_SERIALIZE_IN_PROGRESS)
+ {
+ pa_lock_stream(MyParallelShared->xid, AccessShareLock);
+ pa_unlock_stream(MyParallelShared->xid, AccessShareLock);
+
+ fileset_state = pa_get_fileset_state();
+ Assert(fileset_state == FS_SERIALIZE_DONE);

This is not always true because say due to deadlock, this lock is
released by the leader worker, in that case, the file state will be
still in progress. So, I think we need a change like the below:
diff --git a/src/backend/replication/logical/applyparallelworker.c
b/src/backend/replication/logical/applyparallelworker.c
index 45faa74596..8076786f0d 100644
--- a/src/backend/replication/logical/applyparallelworker.c
+++ b/src/backend/replication/logical/applyparallelworker.c
@@ -686,8 +686,8 @@ pa_spooled_messages(void)
         * the leader had serialized all changes which can lead to undetected
         * deadlock.
         *
-        * The fileset state must be FS_SERIALIZE_DONE once the leader
worker has
-        * finished serializing the changes.
+        * Note that the fileset state can be FS_SERIALIZE_DONE once the leader
+        * worker has finished serializing the changes.
         */
        if (fileset_state == FS_SERIALIZE_IN_PROGRESS)
        {
@@ -695,7 +695,6 @@ pa_spooled_messages(void)
                pa_unlock_stream(MyParallelShared->xid, AccessShareLock);

                fileset_state = pa_get_fileset_state();
-               Assert(fileset_state == FS_SERIALIZE_DONE);

-- 
With Regards,
Amit Kapila.