How to force primary key in ActiveRecord with PostgreSQL to jump start from a specific integer value?

From this: How to make a primary key start from 1000? It seems that I need to issue the SQL command: ALTER TABLE tbl AUTO_INCREMENT = 1000; But I only have been dealing with the database through the ActiveRecord abstraction. Is there a way to achieve it via active record? Either at the time of migration or on the fly when creating new record on the database?

I have tried both the following and failed:

@record= myRecord.new
while @record.id < 1000 do
    @record= myRecord.new
end

It is inefficient but it would just happen once, yet Rails report that @record.id is nil so cannot do the < comparasion and so I try to save the @record first and then see what id (primary key) value it has been assigned by the database

@record.save
if @record.id <1000
    @record.id = 1000 + @record.id
    @record.save!             
end

Somehow rails reports back that one of the unique field in @record is already there so cannot save the @record again.

EDIT: My bad, the above is MySQL command... for PostgreSQL, it seems to be something along the line ( http://archives.postgresql.org/pgsql-general/2006-10/msg01417.php ):

 SELECT setval('id_seq',100111);

However, I tried to run it on the Ruby console of my deployment environment (shared database on Heroku) and I just got !Internal server error back :-( my ruby class is called:

class Mytable < ActiveRecord::Base

so I run this command:

Mytable.connection.execute('SELECT setval('id_seq', 1000)')

and got Internal 开发者_如何学编程server error (tried with both 'id' and 'id_seq' in the above command) But it may be some sort of Ruby on Heroku specific issue that is causing the trouble, so I would investigate and posts another question instead of changing this one. Thanks!

Addition related PostgreSQL command materials:

http://pointbeing.net/weblog/2008/03/mysql-versus-postgresql-adding-an-auto-increment-column-to-a-table.html

http://archives.postgresql.org/pgsql-general/2006-10/msg01417.php

How to reset postgres' primary key sequence when it falls out of sync?

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You can execute raw sql like this:

ActiveRecord::Base.connection.execute('ALTER TABLE tbl AUTO_INCREMENT = 1000');

Or from any descendant of ActiveRecord::Base (i.e. any model class), like this:

MyRecord.connection.execute('ALTER TABLE tbl AUTO_INCREMENT = 1000')