Rails Migration Add_Index issue

Question

I'm trying to add indexing to my users table for the email column. Typing rails g migration add_index_to_users_email generates the migration but the function is empty. The snake casing should be correct, so I'm at a loss as to why the migration is being created but the change function inside is empty.

I've also tried AddIndexToUsersName and the same issue arises.

Any direction on what the issue could be would be greatly appreciated. Only thing I can think of is that I'm using Postgres and not MySQL or SQLite, but that wouldn't matter would it?

Patrick McLaren · Accepted Answer · 2015-05-07 23:40:25Z

1

As far as I know, migration generators only support addition and removal of columns, with a specified modifier. For example, if you wished to add a new string column phone to the users table, you could use the command

rails generate migration AddPhoneToUsers phone:string

Check the Rails Guides for column modifiers. You can try

rails generate migration AddIndexToUsers email:index

to add an index to the existing column. However, I am not sure if generators support column modification. You can write the migration yourself, assuming the email column already exists on the users table:

class AddIndexToUsers < ActiveRecord::Migration
  def change
    add_index :users, :email
  end
end

answered May 7, 2015 at 23:40

Patrick McLaren

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3 Comments

Dipet Over a year ago

Ah, that makes sense. I also see where I errored in assuming my original rails migration would work. I misread Hartl's explanation on what to do. Thanks.

Patrick McLaren Over a year ago

No problem, glad it helped! Quick question, who is Hartl?

Dipet Over a year ago

Hartl, I've really been digging the book. Very in depth giving thorough explanations to everything.

apotry · Accepted Answer · 2015-05-07 23:35:19Z

1

Have a look at:

http://guides.rubyonrails.org/active_record_migrations.html

The correct command is

rails g migration AddIndexToUsers email:string:index

This will generate:

class AddIndexToUsers < ActiveRecord::Migration
  def change
    add_column :users, :email, :string
    add_index :users, :email
  end
end

Edit the migration file and delete the add_column line, then run the migration.

answered May 7, 2015 at 23:35

apotry

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