Re: Logical Replication of sequences - Mailing list pgsql-hackers

From Amit Kapila
Subject Re: Logical Replication of sequences
Date
Msg-id CAA4eK1JfGpCpwN=RMz1CReXe7KKG-eeAxkm5-_1LGVCP52mJjA@mail.gmail.com
Whole thread Raw
In response to Re: Logical Replication of sequences  (Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>)
List pgsql-hackers
On Thu, Jun 6, 2024 at 3:44 PM Ashutosh Bapat
<ashutosh.bapat.oss@gmail.com> wrote:
>
> On Thu, Jun 6, 2024 at 9:22 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>>
>> On Wed, Jun 5, 2024 at 6:01 PM Ashutosh Bapat
>> <ashutosh.bapat.oss@gmail.com> wrote:
>> >
>> > On Wed, Jun 5, 2024 at 8:45 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>> >>
>> >>  How about periodically sending this information?
>> >> >
>> >>
>> >> Now, if we want to support some sort of failover then probably this
>> >> will help. Do you have that use case in mind?
>> >
>> >
>> > Regular failover was a goal for supporting logical replication of sequences. That might be more common than major
upgradescenario. 
>> >
>>
>> We can't support regular failovers to subscribers unless we can
>> replicate/copy slots because the existing nodes connected to the
>> current publisher/primary would expect that. It should be primarily
>> useful for major version upgrades at this stage.
>
>
> We don't want to design it in a way that requires major rework when we are able to copy slots and then support
regularfailover. 
>

I don't think we can just copy slots like we do for standbys. The
slots would require WAL locations to continue, so not sure if we can
make it work for failover for subscribers.

>
 That's when the consistency between a sequence and the table using it
would be a must. So it's better that we take that into consideration
now.
>

With the ideas being discussed here, I could only see the use case of
a major version upgrade or planned switchover to work. If we come up
with any other agreeable way that is better than this then we can
consider the same.

--
With Regards,
Amit Kapila.



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