Re: Perform streaming logical transactions by background workers and parallel apply

Amit Kapila <amit.kapila16@gmail.com>

From: Amit Kapila <amit.kapila16@gmail.com>

To: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>

Cc: Peter Smith <smithpb2250@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, Dilip Kumar <dilipbalaut@gmail.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>

Date: 2022-12-22T12:04:56Z

Lists: 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.
>

Few minor comments:
=================
1.
+       <literal>t</literal> = spill the changes of in-progress
transactions to+       disk and apply at once after the transaction is
committed on the+       publisher,

Can we change this description to: "spill the changes of in-progress
transactions to disk and apply at once after the transaction is
committed on the publisher and received by the subscriber,"

2.
    table is in progress, there will be additional workers for the tables
-   being synchronized.
+   being synchronized. Moreover, if the streaming transaction is applied in
+   parallel, there will be additional workers.

Do we need this change in the first patch? We skip parallel apply
workers from view for the first patch. Am, I missing something?

3.
I think we would need a catversion bump for parallel apply feature
because of below change:
@@ -7913,11 +7913,16 @@ SCRAM-SHA-256$<replaceable>&lt;iteration
count&gt;</replaceable>:<replaceable>&l

      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>substream</structfield> <type>bool</type>
+       <structfield>substream</structfield> <type>char</type>
       </para>

Am, I missing something? If not, then I think we can note that in the
commit message to avoid forgetting it before commit.

4. Kindly change the below comments:
diff --git a/src/backend/replication/logical/applyparallelworker.c
b/src/backend/replication/logical/applyparallelworker.c
index 97f4a3037c..02bb608188 100644
--- a/src/backend/replication/logical/applyparallelworker.c
+++ b/src/backend/replication/logical/applyparallelworker.c
@@ -9,11 +9,10 @@
  *
  * This file contains the code to launch, set up, and teardown a parallel apply
  * worker which receives the changes from the leader worker and
invokes routines
- * to apply those on the subscriber database.
- *
- * This file contains routines that are intended to support setting up, using
- * and tearing down a ParallelApplyWorkerInfo which is required so the leader
- * worker and parallel apply workers can communicate with each other.
+ * to apply those on the subscriber database. Additionally, this file contains
+ * routines that are intended to support setting up, using, and tearing down a
+ * ParallelApplyWorkerInfo which is required so the leader worker and parallel
+ * apply workers can communicate with each other.
  *
  * The parallel apply workers are assigned (if available) as soon as xact's
  * first stream is received for subscriptions that have set their 'streaming'

-- 
With Regards,
Amit Kapila.

Commits

Same data as JSON: 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