Re: Logical Replication of sequences

On Wed, Aug 7, 2024 at 10:12 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>
> This is mostly a repeat of my previous mail from a while ago [1] but
> includes some corrections, answers, and more examples. I'm going to
> try to persuade one last time because the current patch is becoming
> stable, so I wanted to revisit this syntax proposal before it gets too
> late to change anything.
>
> If there is some problem with the proposed idea please let me know
> because I can see only the advantages and no disadvantages of doing it
> this way.
>
> ~~~
>
> The current patchset offers two forms of subscription refresh:
> 1. ALTER SUBSCRIPTION name REFRESH PUBLICATION [ WITH ( refresh_option
> [= value] [, ... ] ) ]
> 2. ALTER SUBSCRIPTION name REFRESH PUBLICATION SEQUENCES
>
> Since 'copy_data' is the only supported refresh_option, really it is more like:
> 1. ALTER SUBSCRIPTION name REFRESH PUBLICATION [ WITH ( copy_data [=
> true|false] ) ]
> 2. ALTER SUBSCRIPTION name REFRESH PUBLICATION SEQUENCES
>
> ~~~
>
> I proposed previously that instead of having 2 commands for refreshing
> subscriptions we should have a single refresh command:
>
> ALTER SUBSCRIPTION name REFRESH PUBLICATION [TABLES|SEQUENCES] [ WITH
> ( copy_data [= true|false] ) ]
>
> Why?
>
> - IMO it is less confusing than having 2 commands that both refresh
> sequences in slightly different ways
>
> - It is more flexible because apart from refreshing everything, a user
> can choose to refresh only tables or only sequences if desired; IMO
> more flexibility is always good.
>
> - There is no loss of functionality from the current implementation
> AFAICT. You can still say "ALTER SUBSCRIPTION sub REFRESH PUBLICATION
> SEQUENCES" exactly the same as the patchset allows.
>
> ~~~
>
> So, to continue this proposal, let the meaning of 'copy_data' for
> SEQUENCES be as follows:
>
> - when copy_data == false: it means don't copy data (i.e. don't
> synchronize anything). Add/remove sequences from pg_subscriber_rel as
> needed.
>
> - when copy_data == true: it means to copy data (i.e. synchronize) for
> all sequences. Add/remove sequences from pg_subscriber_rel as needed)
>

I find overloading the copy_data option more confusing than adding a
new variant for REFRESH. To make it clear, we can even think of
extending the command as ALTER SUBSCRIPTION name REFRESH PUBLICATION
ALL SEQUENCES or something like that. I don't know where there is a
need or not but one can imagine extending it as ALTER SUBSCRIPTION
name REFRESH PUBLICATION SEQUENCES [<seq_name_1>, <seq_name_2>, ..].
This will allow to selectively refresh the sequences.

--
With Regards,
Amit Kapila.