Auto-increment lost during migration.

rubyonrails-talk
1

Hi. I get some strange results when using rename_column on a primary key in a migration. It seems like the migration script removes the auto-increment property if you rename a column.

This is a minimal example.

    create_table :foo, :primary_key => :foo_id do |t|       t.column "name", :string     end

    # renaming the primary key makes auto-increment disappear.     rename_column :foo, :foo_id, :bar_id

Is this a known problem, any beautiful solution available? Maybe use change_column instead?

Best regards, Tobias Nurmiranta

2

Tobias Numiranta wrote:

    create_table :foo, :primary_key => :foo_id do |t|       t.column "name", :string     end

    # renaming the primary key makes auto-increment disappear.     rename_column :foo, :foo_id, :bar_id

What RDBMS are you using? Can you show what the table schema looks like (as reported by the rdbms) before and after the change?

3

Sure. I'm using Mysql. Using mysqldump before and after I get:

before:

CREATE TABLE `foo` (   `foo_id` int(11) NOT NULL auto_increment,   `name` varchar(255) default NULL,   PRIMARY KEY (`foo_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1;

after:

CREATE TABLE `foo` (   `bar_id` int(11) NOT NULL default '0',   `name` varchar(255) default NULL,   PRIMARY KEY (`bar_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Have a nice day, T

4

Tobias Numiranta wrote:

Sure. I'm using Mysql. Using mysqldump before and after I get:

before:

CREATE TABLE `foo` (   `foo_id` int(11) NOT NULL auto_increment,   `name` varchar(255) default NULL,   PRIMARY KEY (`foo_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1;

after:

CREATE TABLE `foo` (   `bar_id` int(11) NOT NULL default '0',   `name` varchar(255) default NULL,   PRIMARY KEY (`bar_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Interesting. I don't use MySQL. What do the logs show as the SQL being issued to MySQL for the change_column migration?

5

Hi. This is the issued SQL:

-- create_table(:foo, {:primary_key=>:foo_id}) CREATE TABLE foo (`foo_id` int(11) DEFAULT NULL auto_increment PRIMARY KEY, `name` varchar(255)) ENGINE=InnoDB

-- rename_column(:foo, :foo_id, :bar_id) SHOW COLUMNS FROM foo LIKE 'foo_id' ALTER TABLE foo CHANGE foo_id bar_id int(11)

Maybe the alter table command need to specify auto_increment, but rails doesn't do so?