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

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On Sun, Oct 15, 2017 at 8:24 PM, Igal @ Lucee.org <igal@lucee.org> wrote:

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

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The correct way to make r_id the primary key would be:

ALTER TABLE event_log
ADD COLUMN r_id SERIAL;

ALTER TABLE event_log
ALTER COLUMN r_id TYPE BIGINT,
ADD CONSTRAINT dummy_pk PRIMARY KEY (r_id);

That automatically generates the column as

r_id bigint NOT NULL DEFAULT nextval('dummy_r_id_seq'::regclass),
CONSTRAINT dummy_pk PRIMARY KEY (r_id)

and creates the appropriate sequence for you.

--
*Melvin Davidson*
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.

Melvin,

On 10/15/2017 5:56 PM, Melvin Davidson wrote:

On Sun, Oct 15, 2017 at 8:24 PM, Igal @ Lucee.org <igal@lucee.org
<mailto:igal@lucee.org>> wrote:

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):

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:

The correct way to make r_id the primary key would be:

ALTER TABLE  event_log
  ADD COLUMN r_id SERIAL;

ALTER TABLE  event_log
  ALTER COLUMN r_id TYPE BIGINT,
  ADD CONSTRAINT dummy_pk PRIMARY KEY (r_id);

That automatically generates the column as

r_id bigint NOT NULL DEFAULT nextval('dummy_r_id_seq'::regclass),
  CONSTRAINT dummy_pk PRIMARY KEY (r_id)

and creates the appropriate sequence for you.

Does that use the new IDENTITY construct that was added in Postgres 10? 
I do not really care for the PRIMARY KEY constraint.  I just want the
sequence with the benefits of the new IDENTITY "type".

Thanks,

Igal

On Sun, Oct 15, 2017 at 9:09 PM, Igal @ Lucee.org <igal@lucee.org> wrote:

Melvin,

On 10/15/2017 5:56 PM, Melvin Davidson wrote:

On Sun, Oct 15, 2017 at 8:24 PM, Igal @ Lucee.org <igal@lucee.org> wrote:

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):

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:

The correct way to make r_id the primary key would be:

ALTER TABLE event_log
ADD COLUMN r_id SERIAL;

ALTER TABLE event_log
ALTER COLUMN r_id TYPE BIGINT,
ADD CONSTRAINT dummy_pk PRIMARY KEY (r_id);

That automatically generates the column as

r_id bigint NOT NULL DEFAULT nextval('dummy_r_id_seq'::regclass),
CONSTRAINT dummy_pk PRIMARY KEY (r_id)

and creates the appropriate sequence for you.

Does that use the new IDENTITY construct that was added in Postgres 10? I
do not really care for the PRIMARY KEY constraint. I just want the
sequence with the benefits of the new IDENTITY "type".

Thanks,

Igal

Does that use the new IDENTITY construct that was added in Postgres 10?

I cannot say, as I do not yet have PostgreSQL 10 installed because it was
very recently released.
However, the method I supplied works for all prior versions of PostgreSQL.

--
*Melvin Davidson*
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.

On 10/15/2017 6:42 PM, Melvin Davidson wrote:

On Sun, Oct 15, 2017 at 9:09 PM, Igal @ Lucee.org <igal@lucee.org
<mailto:igal@lucee.org>> wrote:

Melvin,

On 10/15/2017 5:56 PM, Melvin Davidson wrote:

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):

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:

The correct way to make r_id the primary key would be:

ALTER TABLE  event_log
  ADD COLUMN r_id SERIAL;

ALTER TABLE  event_log
  ALTER COLUMN r_id TYPE BIGINT,
  ADD CONSTRAINT dummy_pk PRIMARY KEY (r_id);

That automatically generates the column as

r_id bigint NOT NULL DEFAULT nextval('dummy_r_id_seq'::regclass),
  CONSTRAINT dummy_pk PRIMARY KEY (r_id)

and creates the appropriate sequence for you.

Does that use the new IDENTITY construct that was added in
Postgres 10?  I do not really care for the PRIMARY KEY
constraint.  I just want the sequence with the benefits of the new
IDENTITY "type".

Does that use the new IDENTITY construct that was added in Postgres 10?

I cannot say, as I do not yet have PostgreSQL 10 installed because it
was very recently released.
However, the method I supplied works for all prior versions of PostgreSQL.

Understood.  But I already had a an auto-increment column by way of
BIGSERIAL.

I want specifically to use the new IDENTITY feature of Postgres 10.

Best,

Igal Sapir
Lucee Core Developer
Lucee.org <http://lucee.org/&gt;