Re: Request for Insights on ID Column Migration Approach

Hi,

Your approach to migrating the ID column from int4 to int8 with minimal
downtime is generally sound but in my option, consider the following also:

- Consider using PostgreSQL's CONCURRENTLY option when creating the
unique index to avoid locking the entire table
- Make sure to first alter the new column to be non-nullable if it’s not
already

On Fri, 27 Sept 2024 at 06:57, Aditya Singh <aditya(dot)singh(at)lji(dot)io> wrote:

> I am just contacting you to talk about a current issue with our database.
> We have run out of a positive sequence in one of our tables and are now
> operating with negative sequences. To address this, we plan to migrate from
> the int4 ID column to an int8 ID column.
>
> The plan involves renaming the int8 column to the id column and setting
> it as the primary key. However, this process will require downtime, which
> may be substantial in a production environment. Fortunately, we have noted
> that other tables do not use the id column as a foreign key, which may
> help mitigate some concerns.
> Our Approach:
>
> 1.
>
> *Create a Unique Index*: We will first create a unique index on the
> new ID column before renaming it and altering it to be non-nullable. This
> step will necessitate scanning the entire table to verify uniqueness.
> 2.
>
> *Add Primary Key*: After ensuring the uniqueness, we will add the ID
> column as the primary key. By doing this, we hope to bypass the additional
> scanning for uniqueness and nullability, as the column will already be set
> as not nullable and will have the uniqueness constraint from the unique
> index.
>
> We want to confirm if this approach will work as expected. If we should be
> aware of any potential pitfalls or considerations, could you please provide
> insights or point us toward relevant documentation?
>
> Thank you so much for your help, and I look forward to your guidance.
>
> Best regards,
>
> Aditya Narayan Singh
> Loyalty Juggernaut Inc.
>
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