# ActiveRecord doesn't find posgresql sequences

**URL:** <https://www.ruby-forum.com/t/activerecord-doesnt-find-posgresql-sequences/69243>\
**Category:** Rails\
**Created:** [September 19, 2006, 5:21pm UTC](https://www.ruby-forum.com/t/activerecord-doesnt-find-posgresql-sequences/69243 "2006-09-19T17:21:46Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![yuleven](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@yuleven](https://www.ruby-forum.com/u/yuleven)\
**Post date:** [September 19, 2006, 5:21pm UTC](https://www.ruby-forum.com/t/activerecord-doesnt-find-posgresql-sequences/69243/1 "2006-09-19T17:21:46Z")

</div>

Hello all,

I used to develop using Rais + Mysql, now I need to switch to  
Postgresql.

I can’t figure out why ActiveRecord cannot find the sequence needed for  
incrementing the id of my table.

The name of the table is users, the name of the sequence is  
users\_id\_seq: (is this the orrect name? )

```
    CREATE TABLE users (
        id int,
        first_name varchar(50),
        constraint users_pkey PRIMARY KEY (id)
    );

    CREATE SEQUENCE users_id_seq
        START WITH 1
        INCREMENT BY 1
        NO MAXVALUE
        NO MINVALUE
        CACHE 1;

```

Well, saving a new records fails:

> ruby script\runner “a = User.new(:first\_name =\> ‘Jack’) ; a.save”  
> c:/ruby/lib/ruby/gems/1.8/gems/rails-1.1.6/lib/commands/runner.rb:27:  
> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/active\_record/connection\_adapters/abstract\_adapter.rb:120:in  
> `log’:  
> RuntimeError: ERROR C23502 Mnull value in column “id” violates  
> not-null constraint FexecMain.c L1806 RExecConstraints:  
> INSERT INTO users (“first\_name”) VALUES(‘Jack’)  
> (ActiveRecord::StatementInvalid)

Ok, well, then I set the sequence manually:

```
    class User < ActiveRecord::Base
      set_sequence_name "users_id_seq"
    end

```

It has no effect! It’s rather annoying.

What am I missing here?

Best regards,  
Yuri

P.S.  
I am using  
postgres-pr (0.4.0)  
rails (1.1.6)  
activerecord (1.14.4)  
postgresql 8.1

---

<div class="post-metadata">

**Author:** ![yuleven](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@yuleven](https://www.ruby-forum.com/u/yuleven)\
**Post date:** [September 19, 2006, 6:06pm UTC](https://www.ruby-forum.com/t/activerecord-doesnt-find-posgresql-sequences/69243/2 "2006-09-19T18:06:26Z")

</div>

Or am I supposed to use

```
id int default nextval('users_id_seq') ?

```

Am I right?

I thought Postgres adaptor will handle it by itself, but I didn’t find  
in in the source code.

Best regards  
Yuri

---

<div class="post-metadata">

**Author:** ![yuleven](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@yuleven](https://www.ruby-forum.com/u/yuleven)\
**Post date:** [September 19, 2006, 9:37pm UTC](https://www.ruby-forum.com/t/activerecord-doesnt-find-posgresql-sequences/69243/3 "2006-09-19T21:37:01Z")

</div>

On 9/19/06, Yuri L. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> Or am I supposed to use
> 
> ```
> id int default nextval('users_id_seq') ?
> 
> ```
> 
> Am I right?
> 
> I thought Postgres adaptor will handle it by itself, but I didn’t find  
> in in the source code.

id must have a default nextval. The postgres adapter will deduce it if  
you  
provide it.

Defining your tables with  
id serial primary key  
is the typical idiom.

jeremy

---

<div class="post-metadata">

**Author:** ![yuleven](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@yuleven](https://www.ruby-forum.com/u/yuleven)\
**Post date:** [September 20, 2006, 11:00am UTC](https://www.ruby-forum.com/t/activerecord-doesnt-find-posgresql-sequences/69243/4 "2006-09-20T11:00:15Z")

</div>

Hi,

Jeremy K. wrote:

> id must have a default nextval. The postgres adapter will deduce it if you  
> provide it.
> 
> Defining your tables with  
> id serial primary key  
> is the typical idiom.

Well, I read the source code of ActiveRecord::Base and the postgres-pr  
adaptor and found out that the deduction you are referring to works  
only for figuring out the id of the record just created:

```
  def insert(sql, name = nil, pk = nil, id_value = nil,

```

sequence\_name = nil) #:nodoc:  
execute(sql, name)  
table = sql.split(" ", 4)[2]  
id\_value || last\_insert\_id(table, sequence\_name ||  
default\_sequence\_name(table, pk))  
end

Well, that’s ok, I’m fine with the rdbms taking care of incrementing  
the pk, I just had false expectations about Active Record, because in  
some O/R Mappers I used in the past (OJB) you can configure it to take  
care of the PKs.

Well, problem’s solved, no, there’s no problem, I’m pretty happy with  
ActiveRecord.

Yuri