How can I rename a database column in a Ruby on Rails migration?

Question

I wrongly named a column hased_password instead of hashed_password.

How do I update the database schema, using migration to rename this column?

Answer 1

Could be a better idea than rename a column, create a new column and copy the content:

with this way we can save the content in the old column

this could be the generation:

rails generate migration add_birthdate_to_User birthdate:string

this could be the migration:

class AddBirthdateToUser < ActiveRecord::Migration[7.0]
  def change
    add_column :user, :birthdate, :json, default: '[]', null: false

    reversible do |dir|
      dir.up do
        User.update_all('birthdate=birtdate') # rubocop:disable Rails/SkipsModelValidations
      end
    end
  end
end

after that you have to remove the wrong column 'Birtdate'

class RemoveBirthdateFromUser < ActiveRecord::Migration[7.0]
  def change
    remove_column :User, :Birtdate, :json
  end
end

Answer 2

rename_column :table, :old_column, :new_column

You'll probably want to create a separate migration to do this. (Rename FixColumnName as you will.):

bin/rails generate migration FixColumnName
# creates  db/migrate/xxxxxxxxxx_fix_column_name.rb

Then edit the migration to do your will:

# db/migrate/xxxxxxxxxx_fix_column_name.rb
class FixColumnName < ActiveRecord::Migration
  def self.up
    rename_column :table_name, :old_column, :new_column
  end

  def self.down
    # rename back if you need or do something else or do nothing
  end
end

---

For Rails 3.1 use:

While, the up and down methods still apply, Rails 3.1 receives a change method that "knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method".

See "Active Record Migrations" for more information.

rails g migration FixColumnName

class FixColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

If you happen to have a whole bunch of columns to rename, or something that would have required repeating the table name over and over again:

rename_column :table_name, :old_column1, :new_column1
rename_column :table_name, :old_column2, :new_column2
...

You could use change_table to keep things a little neater:

class FixColumnNames < ActiveRecord::Migration
  def change
    change_table :table_name do |t|
      t.rename :old_column1, :new_column1
      t.rename :old_column2, :new_column2
      ...
    end
  end
end

Then just db:migrate as usual or however you go about your business.

---

For Rails 4:

While creating a Migration for renaming a column, Rails 4 generates a change method instead of up and down as mentioned in the above section. The generated change method is:

$ > rails g migration ChangeColumnName

which will create a migration file similar to:

class ChangeColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

Answer 3

I had this challenge when working on a Rails 6 application with a PostgreSQL database.

Here's how I fixed it:

In my case the table_name was "Products", the old_column was "SKU" and the new_column was "ProductNumber".

1. Create a migration file that will contain the command for renaming the column:

    rails generate migration RenameSKUToProductNumberInProducts
   

2. Open the migration file in the db/migrate directory:

    db/migrate/20201028082344_rename_sku_to_product_number_in_products.rb
   

3. Add the command for renaming the column:

    class RenameSkuToProductNumberInProducts < ActiveRecord::Migration[6.0]
      def change
        # rename_column :table_name, :old_column, :new_column
        rename_column :products, :sku, :product_number
      end
    end
   

4. Save, and then run the migration command:

    rails db:migrate
   

You can now confirm the renaming of the column by taking a look at the schema file:

    db/schema.rb

If you are not satisfied with the renaming of the column, you can always rollback:

    rails db:rollback

Note: Endeavour to modify the column name to the new name in all the places where it is called.

Answer 4

Just generate the migration using:

rails g migration rename_hased_password

After that edit the migration and add the following line in the change method:

rename_column :table, :hased_password, :hashed_password

This should do the trick.

Answer 5

A close cousin of create_table is change_table, used for changing existing tables. It is used in a similar fashion to create_table but the object yielded to the block knows more tricks. For example:

class ChangeBadColumnNames < ActiveRecord::Migration
  def change
    change_table :your_table_name do |t|
      t.rename :old_column_name, :new_column_name
    end
  end
end

This way is more efficient if we use it with other alter methods such as: remove/add index/remove index/add column. We can do things like:

Rename

t.rename :old_column_name, :new_column_name

Add column

t.string :new_column

Remove column

t.remove :removing_column

Index column

t.index :indexing_column

Answer 6

Generate the migration file:

rails g migration FixName

which creates db/migrate/xxxxxxxxxx.rb.

Edit the migration to do your will:

class FixName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

Answer 7

If you need to switch column names you will need to create a placeholder to avoid a "duplicate column name" error. Here's an example:

class SwitchColumns < ActiveRecord::Migration
  def change
    rename_column :column_name, :x, :holder
    rename_column :column_name, :y, :x
    rename_column :column_name, :holder, :y
  end
end

Answer 8

As an alternative option, if you are not married to the idea of migrations, there is a compelling gem for ActiveRecord which will handle the name changes automatically for you, Datamapper style. All you do is change the column name in your model, and make sure you put Model.auto_upgrade! at the bottom of your model.rb, and viola! The database is updated on the fly.

See https://github.com/DAddYE/mini_record

Note: You will need to nuke db/schema.rb to prevent conflicts.

It is still in the beta phase and obviously not for everyone, but it is still a compelling choice. I am currently using it in two non-trivial production apps with no issues.

Answer 9

Some versions of Ruby on Rails support the up/down methods for migration and if you have an up/down method in your migration, then:

def up
    rename_column :table_name, :column_old_name, :column_new_name
end

def down
    rename_column :table_name, :column_new_name, :column_old_name
end

If you have the change method in your migration, then:

def change
    rename_column :table_name, :column_old_name, :column_new_name
end

For more information see: Ruby on Rails - Migrations or Active Record Migrations.

Answer 10

From the API:

rename_column(table_name, column_name, new_column_name)

This renames a column but keeps the type and content remains the same.

Answer 11

Run this command to create a migration file:

rails g migration ChangeHasedPasswordToHashedPassword

Then in the file generated in the db/migrate folder, write rename_column as below:

class ChangeOldColumnToNewColumn < ActiveRecord::Migration
  def change
     rename_column :table_name, :hased_password, :hashed_password
  end
end

Answer 12

See the "Available Transformations" section in the "Active Record Migrations" documentation.

rename_column(table_name, column_name, new_column_name):

Renames a column but keeps the type and content.

Answer 13

In the console:

rails generate migration newMigration

In the newMigration file:

class FixColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

Answer 14

First you need to run

rails g migration create_new_column_in_tablename new_column:datatype
rails g migration remove_column_in_tablename old_column:datatype

and then you need to check db/migration you can check the details in the nem migration, if all the details is correct you need to run:

rails db:migrate

Answer 15

rails g migration migrationName

So you go to your generated migration and add:

rename_column :table, :old_column, :new_column

to the method

Answer 16

You can write a migration run the below command to update the column name:

rename_column :your_table_name, :hased_password, :hashed_password

Also, make sure that you update any usage of the old column name in your code with the new one.

Answer 17

In my opinion, in this case, it's better to use rake db:rollback, then edit your migration and again run rake db:migrate.

However, if you have data in the column you don't want to lose, then use rename_column.

Answer 18

Let's KISS. All it takes is three simple steps. The following works for Rails 5.2.

1 . Create a Migration

• rails g migration RenameNameToFullNameInStudents

• rails g RenameOldFieldToNewFieldInTableName - that way it is perfectly clear to maintainers of the code base later on. (use a plural for the table name).

2. Edit the migration

# I prefer to explicitly write theupanddownmethods.

# ./db/migrate/20190114045137_rename_name_to_full_name_in_students.rb

class RenameNameToFullNameInStudents < ActiveRecord::Migration[5.2]
  def up
    # rename_column :table_name, :old_column, :new_column
    rename_column :students, :name, :full_name
  end

  def down
            # Note that the columns are reversed
    rename_column :students, :full_name, :name
  end
end

3. Run your migrations

rake db:migrate

And you are off to the races!

Answer 19

I'm on rails 5.2, and trying to rename a column on a devise User.

the rename_column bit worked for me, but the singular :table_name threw a "User table not found" error. Plural worked for me.

rails g RenameAgentinUser

Then change migration file to this:

rename_column :users, :agent?, :agent

Where :agent? is the old column name.

Answer 20

Rails 5 migration changes

eg:

rails g model Student student_name:string age:integer

if you want to change student_name column as name

Note:- if you not run rails db:migrate

You can do following steps

rails d model Student student_name:string age:integer

This will remove generated migration file, Now you can correct your column name

rails g model Student name:string age:integer

If you migrated(rails db:migrate), following options to change column name

rails g migration RemoveStudentNameFromStudent student_name:string

rails g migration AddNameToStudent name:string

Answer 21

 def change
    rename_column :table_name, :old_column_name, :new_column_name
  end

Answer 22

Run rails g migration ChangesNameInUsers (or whatever you would like to name it)

Open the migration file that has just been generated, and add this line in the method (in between def change and end):

rename_column :table_name, :the_name_you_want_to_change, :the_new_name

Save the file, and run rake db:migrate in the console

Check out your schema.db in order to see if the name has actually changed in the database!

Hope this helps :)

Answer 23

$:  rails g migration RenameHashedPasswordColumn
invoke  active_record
      create    db/migrate/20160323054656_rename_hashed_password_column.rb

Open that migration file and modify that file as below(Do enter your original table_name)

class  RenameHashedPasswordColumn < ActiveRecord::Migration
  def change
    rename_column :table_name, :hased_password, :hashed_password
  end
end

Answer 24

You have two ways to do this:

1. In this type it automatically runs the reverse code of it, when rollback.

   def change
     rename_column :table_name, :old_column_name, :new_column_name
   end
   

2. To this type, it runs the up method when rake db:migrate and runs the down method when rake db:rollback:

   def self.up
     rename_column :table_name, :old_column_name, :new_column_name
   end
   
   def self.down
     rename_column :table_name,:new_column_name,:old_column_name
   end
   

Answer 25

Generate a Ruby on Rails migration:

$:> rails g migration Fixcolumnname

Insert code in the migration file (XXXXXfixcolumnname.rb):

class Fixcolumnname < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

Answer 26

Open your Ruby on Rails console and enter:

ActiveRecord::Migration.rename_column :tablename, :old_column, :new_column

Answer 27

For Ruby on Rails 4:

def change
    rename_column :table_name, :column_name_old, :column_name_new
end

Answer 28

Manually we can use the below method:

We can edit the migration manually like:

• Open app/db/migrate/xxxxxxxxx_migration_file.rb

• Update hased_password to hashed_password

• Run the below command

  $> rake db:migrate:down VERSION=xxxxxxxxx
  

Then it will remove your migration:

$> rake db:migrate:up VERSION=xxxxxxxxx

It will add your migration with the updated change.

Answer 29

Simply create a new migration, and in a block, use rename_column as below.

rename_column :your_table_name, :hased_password, :hashed_password

Answer 30

If the present data is not important for you, you can just take down your original migration using:

rake db:migrate:down VERSION='YOUR MIGRATION FILE VERSION HERE'

Without the quotes, then make changes in the original migration and run the up migration again by:

rake db:migrate