Re: Non blocking type change for primary column

>
> 1. adding a new nullable column of type bigint.
> 2. copying the primary key into this field in small batches
> 3. Once done. rename the primary column and new column, to swap them
> 4. attach the sequence to the new column and deattach it from the old
> column
> 5. Make new column NON NULL (Not sure if this will block)
> 6. Remove primary key from old column, make new column to be the primary
> key (I fear this will block to create the index, but I guess not nearly
> as long as ALTER COLUMN type)
> 7. Delete old column.
>
> This could be prevented, if this would be done in a non blocking way by
> the database system itself, so I hope this is already implemented or at
> least on the roadmap.
> Any thoughts?

Hye Torge,

I was recently involved with such a change. See this thread[1] for
discussion. In particular, it touches on point 5, where you ask what's
blocking. Hope it helps.

[1]
https://www.postgresql.org/message-id/flat/CABZeWdybDVTgCQFZf0jDtj0p4yLxNrYd8aw61iFxY-Xt%2BfqPkw%40mail.gmail.com