Horton

RE: logical replication empty transactions

Yu Shi (Fujitsu) <shiy.fnst@fujitsu.com>

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From: "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>
To: Ajin Cherian <itsajin@gmail.com>
Cc: Peter Smith <smithpb2250@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, "osumi.takamichi@fujitsu.com" <osumi.takamichi@fujitsu.com>, vignesh C <vignesh21@gmail.com>, Michael Paquier <michael@paquier.xyz>, Rahila Syed <rahila.syed@2ndquadrant.com>, Dilip Kumar <dilipbalaut@gmail.com>, Jeff Janes <jeff.janes@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Craig Ringer <craig@2ndquadrant.com>
Date: 2022-03-07T08:50:42Z
Lists: pgsql-hackers 
On Fri, Mar 4, 2022 9:41 AM Ajin Cherian <itsajin@gmail.com> wrote:
> 
> I have split the patch into two. I have kept the logic of skipping
> streaming changes in the second patch.
> I will work on the second patch once we can figure out a solution for
> the COMMIT PREPARED after restart problem.
> 

Thanks for updating the patch.

A comment on v23-0001 patch.

@@ -1429,6 +1520,19 @@ pgoutput_message(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 	if (in_streaming)
 		xid = txn->xid;
 
+	/*
+	 * Output BEGIN if we haven't yet.
+	 * Avoid for non-transactional messages.
+	 */
+	if (in_streaming || transactional)
+	{
+		PGOutputTxnData *txndata = (PGOutputTxnData *) txn->output_plugin_private;
+
+		/* Send BEGIN if we haven't yet */
+		if (txndata && !txndata->sent_begin_txn)
+			pgoutput_send_begin(ctx, txn);
+	}
+
 	OutputPluginPrepareWrite(ctx, true);
 	logicalrep_write_message(ctx->out,
 							 xid,

I think we don't need to send BEGIN if in_streaming is true, right? The first
patch doesn't skip streamed transaction, so should we modify
+	if (in_streaming || transactional)
to
+	if (!in_streaming && transactional)
?

Regards,
Shi yu

Commits

  1. Skip empty transactions for logical replication.

  2. Add decoding of sequences to built-in replication

  3. Allow specifying row filters for logical replication of tables.