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

rename_column :table, :old_column, :new_column

Update:

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

script/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

---

An update for Rails 3.1

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"

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

Thank you, Luke && Turadg, for bringing up the topic.

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

---

An update for Rails 4

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

$ > rails g migration ChangeColumnName

which will create a migration file similar to this :

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

Answer 2

IMO, in this case, better use rake db:rollback. Then edit your migration and again type rake db:migrate. However, if you have data in the column you don't want to lose, then use rename_column.

Answer 3

If the column is already populated with data and live in production, I'd recommend a step by step approach, so as to avoid downtime in production while waiting for the migrations.

First I'd create a db migration to add columns with the new name(s) and populate them with the values from the old column name.

class AddCorrectColumnNames < ActiveRecord::Migration
  def up
    add_column :table, :correct_name_column_one, :string
    add_column :table, :correct_name_column_two, :string

    puts 'Updating correctly named columns'
    execute "UPDATE table_name SET correct_name_column_one = old_name_column_one, correct_name_column_two = old_name_column_two"
    end
  end

  def down
    remove_column :table, :correct_name_column_one
    remove_column :table, :correct_name_column_two
  end
end

Then I'd commit just that change, and push the change into production.

git commit -m 'adding columns with correct name'

Then once the commit has been pushed into production, I'd run.

Production $ bundle exec rake db:migrate

Then I'd update all of the views/controllers that referenced the old column name to the new column name. Run through my test suite, and commit just those changes. (After making sure it was working locally and passing all tests first!)

git commit -m 'using correct column name instead of old stinky bad column name'

Then I'd push that commit to production.

At this point you can remove the original column without worrying about any sort of downtime associated with the migration itself.

class RemoveBadColumnNames < ActiveRecord::Migration
  def up
    remove_column :table, :old_name_column_one
    remove_column :table, :old_name_column_two
  end

  def down
    add_column :table, :old_name_column_one, :string
    add_column :table, :old_name_column_two, :string
  end
end

Then push this latest migration to production and run bundle exec rake db:migrate in the background.

I realize this is a bit more involved of a process, but I'd rather do this than have issues with my production migration.

Answer 4

http://api.rubyonrails.org/classes/ActiveRecord/Migration.html

Under Available Transformations

rename_column(table_name, column_name, new_column_name):

Renames a column but keeps the type and content.

Answer 5

Run the below 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 ChangeOldCoulmnToNewColumn < ActiveRecord::Migration
  def change
     rename_column :table_name, :hased_password, :hashed_password
  end
end

Answer 6

From API:

rename_column(table_name, column_name, new_column_name)

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

Answer 7

Some versions of Ruby on Rails support to up/down method to migration and if you have 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 you can move: Ruby on Rails - Migrations or Active Record Migrations.

Answer 8

If your code is not shared with other one, then best option is to do just rake db:rollback then edit your column name in migration and rake db:migrate. Thats it

And you can write another migration to rename the column

 def change
    rename_column :table_name, :old_name, :new_name
  end

Thats it.

Answer 9

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 10

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! Database is updated on the fly.

https://github.com/DAddYE/mini_record

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

Still in beta phases and obviously not for everyone but still a compelling choice (I am currently using it in two non-trivial production apps with no issues)

Answer 11

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

Answer 12

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

rename_column :your_table_name, :hased_password, :hashed_password

Answer 13

For Ruby on Rails 4:

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

Answer 14

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 15

Generate the migration file:

rails g migration FixName

# 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 16

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 17

$:  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 18

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

Answer 19

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 20

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 21

Open your Ruby on Rails console and enter:

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

Answer 22

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 23

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 24

Just generate migration using command

rails g migration rename_hased_password

After that edit the migration add following line in change method

rename_column :table, :hased_password, :hashed_password

This should do the trick.

Answer 25

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 26

Update - 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 do with other alter methods such as: remove/add index/remove index/add column, eg we can do further 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
#...