Re: Alter the column data type of the large data volume table.

On Wed, Dec 2, 2020 at 11:53 PM charles meng <xlyybz(at)gmail(dot)com> wrote:

> Hi all,
>
> I have a table with 1.6 billion records. The data type of the primary key
> column is incorrectly used as integer. I need to replace the type of the
> column with bigint. Is there any ideas for this?
>
> Solutions that have been tried:
> Adding temporary columns was too time-consuming, so I gave up.
> Using a temporary table, there is no good way to migrate the original
> table data to the temporary table
>
> Thanks in advance.
>

You can add a new column with NO default value and null as default and have
it be very fast. Then you can gradually update rows in batches (if on
PG11+, perhaps use do script with a loop to commit after X rows) to set the
new column the same as the primary key. Lastly, in a transaction, update
any new rows where the bigint column is null, and change which column is
the primary key & drop the old one. This should keep each transaction
reasonably sized to not hold up other processes.