Horton

Re: logical replication empty transactions

Ajin Cherian <itsajin@gmail.com>

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From: Ajin Cherian <itsajin@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: "osumi.takamichi@fujitsu.com" <osumi.takamichi@fujitsu.com>, Peter Smith <smithpb2250@gmail.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: 2022-02-25T11:19:02Z
Lists: pgsql-hackers

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On Fri, Feb 18, 2022 at 9:27 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
>
> Yeah, I think there could be multiple ways (a) We can send such a keep
> alive in WalSndUpdateProgress() itself by using ctx->write_location.
> For this, we need to modify WalSndKeepalive() to take sentPtr as
> input. (b) set some flag in WalSndUpdateProgress() and then do it
> somewhere in WalSndLoop probably in WalSndKeepaliveIfNecessary, or
> maybe there is another better way.
>

Thanks for the suggestion Amit and Osumi-san, I experimented with both
the suggestions but finally decided to use
 (a)Modifying WalSndKeepalive() to take an LSN optionally as input and
passed in the  ctx->write_location.

I also verified that if I block the WalSndKeepalive() in
WalSndWaitForWal, then my new code sends the keepalive
when skipping transactions and the syncrep gets back feedback..

I will address comments from Peter and Wang in my next patch update.

regards,
Ajin Cherian
Fujitsu Australia

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.