Re: Perform streaming logical transactions by background workers and parallel apply
Amit Kapila <amit.kapila16@gmail.com>
On Tue, Dec 13, 2022 at 4:36 AM Peter Smith <smithpb2250@gmail.com> wrote:
>
> ~~~
>
> 3. pa_set_stream_apply_worker
>
> +/*
> + * Set the worker that required to apply the current streaming transaction.
> + */
> +void
> +pa_set_stream_apply_worker(ParallelApplyWorkerInfo *winfo)
> +{
> + stream_apply_worker = winfo;
> +}
>
> Comment wording seems wrong.
>
I think something like "Cache the parallel apply worker information."
may be more suitable here.
Few more similar cosmetic comments:
1.
+ /*
+ * Unlock the shared object lock so that the parallel apply worker
+ * can continue to receive changes.
+ */
+ if (!first_segment)
+ pa_unlock_stream(winfo->shared->xid, AccessExclusiveLock);
This comment is missing in the new (0002) patch.
2.
+ if (!winfo->serialize_changes)
+ {
+ if (!first_segment)
+ pa_unlock_stream(winfo->shared->xid, AccessExclusiveLock);
I think we should write some comments on why we are not unlocking when
serializing changes.
3. Please add a comment like below in the patch to make it clear why
in stream_abort case we perform locking before sending the message.
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -1858,6 +1858,13 @@ apply_handle_stream_abort(StringInfo s)
* worker will wait on the lock for the next
set of changes after
* processing the STREAM_ABORT message if it
is not already waiting
* for STREAM_STOP message.
+ *
+ * It is important to perform this locking
before sending the
+ * STREAM_ABORT message so that the leader can
hold the lock first
+ * and the parallel apply worker will wait for
the leader to release
+ * the lock. This is the same as what we do in
+ * apply_handle_stream_stop. See Locking
Considerations atop
+ * applyparallelworker.c.
*/
if (!toplevel_xact)
--
With Regards,
Amit Kapila.
Commits
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the thread's linked commits as JSON, with link sources.
API reference →
-
Fix invalid memory access during the shutdown of the parallel apply worker.
- 3d144c6c8602 16.0 landed
-
Fix assertion failure in apply worker.
- de63f8dadee4 16.0 landed
-
Use elog to report unexpected action in handle_streamed_transaction().
- 781ac42d43ab 16.0 landed
-
Use appropriate wait event when sending data in the apply worker.
- d9d7fe68d35e 16.0 landed
-
Allow the logical_replication_mode to be used on the subscriber.
- 9f2213a7c575 16.0 landed
-
Rename GUC logical_decoding_mode to logical_replication_mode.
- 1e8b61735cfb 16.0 landed
-
Display the leader apply worker's PID for parallel apply workers.
- d540a02a724b 16.0 landed
-
Improve the code to decide and process the apply action.
- c981d9145dea 16.0 landed
-
Document the newly added wait events added by commit 216a784829.
- cd06ccd78fcf 16.0 landed
-
Perform apply of large transactions by parallel workers.
- 216a784829c2 16.0 landed
-
Wake up a subscription's replication worker processes after DDL.
- c6e1f62e2cee 16.0 cited
-
Add copyright notices to meson files
- 8284cf5f746f 16.0 cited
-
Better document logical replication parameters
- a8500750ca0a 16.0 cited
-
Add a common function to generate the origin name.
- 776e1c8a5d14 16.0 cited
-
Harmonize parameter names in storage and AM code.
- bfcf1b34805f 16.0 cited
-
Avoid using list_length() to test for empty list.
- efd0c16becbf 16.0 cited
-
Improve two comments related to a boolean DefElem's value
- 8445f5a21d40 16.0 cited
-
Fix partition table's REPLICA IDENTITY checking on the subscriber.
- 26b3455afaa9 15.0 cited
-
Fix data inconsistency between publisher and subscriber.
- b7658c24c7c1 15.0 cited
-
Fix cache look-up failures while applying changes in logical replication.
- 5a97b1325453 15.0 cited