Re: Perform streaming logical transactions by background workers and parallel apply
Amit Kapila <amit.kapila16@gmail.com>
On Thu, Sep 22, 2022 at 8:59 AM wangw.fnst@fujitsu.com
<wangw.fnst@fujitsu.com> wrote:
>
Few comments on v33-0001
=======================
1.
+ else if (data->streaming == SUBSTREAM_PARALLEL &&
+ data->protocol_version < LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM)
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ errmsg("requested proto_version=%d does not support
streaming=parallel mode, need %d or higher",
+ data->protocol_version, LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM)));
I think we can improve this error message as: "requested
proto_version=%d does not support parallel streaming mode, need %d or
higher".
2.
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -3184,7 +3184,7 @@ SELECT pid, wait_event_type, wait_event FROM
pg_stat_activity WHERE wait_event i
</para>
<para>
OID of the relation that the worker is synchronizing; null for the
- main apply worker
+ main apply worker and the apply parallel worker
</para></entry>
</row>
This and other changes in monitoring.sgml refers the workers as "apply
parallel worker". Isn't it better to use parallel apply worker as we
are using at other places in the patch? But, I have another question,
do we really need to display entries for parallel apply workers in
pg_stat_subscription if it doesn't have any meaningful information? I
think we can easily avoid it in pg_stat_get_subscription by checking
apply_leader_pid.
3.
ApplyWorkerMain()
{
...
...
+
+ if (server_version >= 160000 &&
+ MySubscription->stream == SUBSTREAM_PARALLEL)
+ options.proto.logical.streaming = pstrdup("parallel");
After deciding here whether the parallel streaming mode is enabled or
not, we recheck the same thing in apply_handle_stream_abort() and
parallel_apply_can_start(). In parallel_apply_can_start(), we do it
via two different checks. How about storing this information say in
structure MyLogicalRepWorker in ApplyWorkerMain() and then use it at
other places?
--
With Regards,
Amit Kapila.
Commits
GET /api/v1/messages/:b64id/commits
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