Re: Column type modification in big tables

On Tue, Aug 13, 2024 at 7:39 PM Greg Sabino Mullane <htamfids(at)gmail(dot)com>
wrote:

> On Sat, Aug 10, 2024 at 5:06 PM Lok P <loknath(dot)73(at)gmail(dot)com> wrote:
>
>
>> Can someone through some light , in case we get 5-6hrs downtime for this
>> change , then what method should we choose for this Alter operation?
>>
>
> We can't really answer that. Only you know what resources you have, what
> risk/reward you are willing to handle, and how long things may take. For
> that latter item, your best bet is to try this out on the same/similar
> hardware and see how long it takes. Do a smaller table and extrapolate if
> you need to. Or promote one of your replicas offline and modify that. I've
> given you a low-risk / medium-reward option with check constraints, but for
> the ALTER TABLE options you really need to try it and see (on non-prod).
>
>
*"Do a smaller table and extrapolate if you need to. Or promote one of your
replicas offline and modify that. I've given you a low-risk / medium-reward
option with check constraints, but for the ALTER TABLE options you really
need to try it and see (on non-prod)."*

Is there any possible method(maybe by looking into the data dictionary
tables/views etc) to see the progress of the Alter statement by which we
can estimate the expected completion time of the "Alter" command? I
understand pg_stat_activity doesn't show any completion percentage of a
statement, but wondering if by any other possible way we can estimate the
amount of time it will take in prod for the completion of the ALTER command.