Re: Adding identity column to a non-empty table

On 10/15/2017 4:01 PM, Igal @ Lucee.org wrote:
>
> Hello,
>
> I'm trying to add an identity column to a table that has records
> (previously had a bigserial column which I removed):
>
>   ALTER TABLE event_log
> ADD COLUMN r_id BIGINT GENERATED BY DEFAULT AS IDENTITY;
>
> But I'm getting an error `column r_id contains null values`.
>
> How can I add the column and populate it for the existing rows?
>

There is probably a better solution, but the one I came up with is to
add the column as BIGSERIAL and DROP the SEQUENCE CASCADE, SELECT the
max(rid) + 1, and then convert the column to IDENTITY:

  ALTER TABLE transient.event_log ADD COLUMN r_id BIGSERIAL;

  -- find the sequence name and then
  DROP sequence <sequence-name> CASCADE;

  -- find min value by executing select max(r_id) + 1
  ALTER table transient.event_log
      ALTER COLUMN r_id
          ADD GENERATED BY DEFAULT AS IDENTITY (MINVALUE <min-value>);

If anyone has a better suggestion then please let me know.

Thanks,

Igal