What&#39;s the syntax for dropping a database table column through a [Rails migration](https://guides.rubyonrails.org/active_record_migrations.html)?

How to drop columns using Rails migration

A user has many uploads. I want to add a column to the `uploads` table that references the `user`. What should the migration look like? 

Here is what I have. I&#39;m not sure if I should use (1) `:user_id, :int` or (2) `:user, :references`. I&#39;m not even sure if (2) works. Just trying to do this the &quot;rails&quot; way.

    class AddUserToUploads &lt; ActiveRecord::Migration
      def change
      	add_column :uploads, :user_id, :integer
      end
    end

Relevant question except for Rails 3. https://stackoverflow.com/questions/4954969/rails-3-migrations-adding-reference-column

Add a reference column migration in Rails 4

I have a rake task that won&#39;t work unless a table exists. I&#39;m working with more than 20 engineers on a website so I want to make sure they have migrated the table before they can do a rake task which will populate that respective table.

Does AR have a method such as `Table.exists`? How can I make sure they have migrated the table successfully?

Check if a table exists in Rails

I have the problem, that I have an migration in Rails that sets up a default setting for a column, like this example:

    def self.up
      add_column :column_name, :bought_at, :datetime, :default =&gt; Time.now
    end

Suppose, I like to drop that default settings in a later migration, how do I do that with using rails migrations?

My current workaround is the execution of a custom sql command in the rails migration, like this:

    def self.up
      execute &#39;alter table column_name alter bought_at drop default&#39;
    end

But I don&#39;t like this approach, because I am now dependent on how the underlying database is interpreting this command. In case of a change of the database this query perhaps might not work anymore and the migration would be broken. So, is there a way to express the undo of a default setting for a column in rails?

Rails migrations: Undo default setting for a column

I need to add timestamps (`created_at` &amp; `updated_at`) to an existing table. I tried the following code but it didn&#39;t work.

    class AddTimestampsToUser &lt; ActiveRecord::Migration
        def change_table
            add_timestamps(:users)
        end
    end

Add timestamps to an existing table

Is there a rake task that shows the pending migrations in a rails app?

Show pending migrations in rails

I want to make a `migration` in Rails, referencing another table. Usually, I would do something like:

    add_column :post, :user, :references

This creates a column named `user_id` in `posts` table. But what if, instead of `user_id`, I want something like `author_id`? How can I do that?

Specifying column name in a &quot;references&quot; migration

I have a Products table and want to add a column:

    t.references :imageable, :polymorphic =&gt; true

I was trying to generate migration for this by doing:

    $ rails generate migration AddImageableToProducts imageable:references:polymorphic

but I am obviously doing it wrong. Can anybody make any suggestion? Thanks

When I try to manually put it in after generating the migration, I did it like this:


    class AddImageableToProducts &lt; ActiveRecord::Migration
      def self.up
        add_column :products, :imageable, :references, :polymorphic =&gt; true
      end
    
      def self.down
        remove_column :products, :imageable
      end
    end

and it still hasn&#39;t worked

how to generate migration to make references polymorphic

What is the difference between `t.references` and `t.belongs_to`?
Why are we having those two different words? It seems to me they do the same thing?
Tried some Google search, but find no explanation.

    class CreateFoos &lt; ActiveRecord::Migration
      def change
        create_table :foos do |t|
          t.references :bar
          t.belongs_to :baz
          # The two above seems to give similar results
          t.belongs_to :fooable, :polymorphic =&gt; true
          # I have not tried polymorphic with t.references
          t.timestamps
        end
      end
    end


What is the difference between t.belongs_to and t.references in rails?

Looks like the new rails version has &quot;change&quot; versus self.up and self.down methods.

So what happens when one has to roll back a migration how does it know what actions to perform. I have the following method that I need to implement based on an online tutorial:

    class AddImageToUsers &lt; ActiveRecord::Migration
      def self.up
        add_column :users, :image_file_name, :string
        add_column :users, :image_content_type, :string
        add_column :users, :image_file_size, :integer
        add_column :users, :image_updated_at, :datetime
      end
    
      def self.down
        remove_column :users, :image_file_name, :string
        remove_column :users, :image_content_type, :string
        remove_column :users, :image_file_size, :integer
        remove_column :users, :image_updated_at, :datetime
      end    
    end

How can I do the same using the new change method?

Rails migrations: self.up and self.down versus change

How do you roll back a failed rails migration? I would expect that `rake db:rollback` would undo the failed migration, but no, it rolls back the previous migration (the failed migration minus one). And `rake db:migrate:down VERSION=myfailedmigration` doesn&#39;t work either. I&#39;ve ran into this a few times and it&#39;s very frustrating. Here&#39;s a simple test I made to duplicate the problem:

    class SimpleTest &lt; ActiveRecord::Migration
      def self.up
        add_column :assets, :test, :integer
        # the following syntax error will cause the migration to fail
        add_column :asset, :test2, :integer
      end
    
      def self.down
        remove_column :assets, :test
        remove_column :assets, :test2
      end
    end

result:

&lt;pre&gt;
==  SimpleTest: migrating =====================================================
-- add_column(:assets, :test, :integer)
   -&gt; 0.0932s
-- add_column(:asset, :error)
rake aborted!
An error has occurred, all later migrations canceled:

wrong number of arguments (2 for 3)
&lt;/pre&gt;

ok, lets roll it back:

&lt;pre&gt;
$ rake db:rollback
==  AddLevelsToRoles: reverting ===============================================
-- remove_column(:roles, :level)
   -&gt; 0.0778s
==  AddLevelsToRoles: reverted (0.0779s) ======================================
&lt;/pre&gt;

huh? that was my last migration before SimpleTest, not the failed migration. (And oh, it would be nice if the migration output included the version number.)

So lets try running the down for the failed migration SimpleTest:

&lt;pre&gt;
$ rake db:migrate:down VERSION=20090326173033
$
&lt;/pre&gt;

Nothing happens, and no output either. But maybe it ran the migration anyway? So lets fix the syntax error in the SimpleTest migration, and try to run it again. 

&lt;pre&gt;
$ rake db:migrate:up VERSION=20090326173033
==  SimpleTest: migrating =====================================================
-- add_column(:assets, :test, :integer)
rake aborted!
Mysql::Error: Duplicate column name &#39;test&#39;: ALTER TABLE `assets` ADD `test` int(11)
&lt;/pre&gt;

Nope. Obviously the migrate:down didn&#39;t work. It&#39;s not failing, it&#39;s just not executing.

No way to get rid of that duplicate table other than manually going into the database and removing it, and then running the test. There&#39;s got to be a better way than that.


Rolling back a failed Rails migration

I have the following two Models:

    class Store &lt; ActiveRecord::Base
        belongs_to :person
    end

    class Person &lt; ActiveRecord::Base
        has_one :store
    end


Here is the issue: I am trying to create a migration to create the foreign key within the people table. However, the column referring to the foreign key of Store is not named *store_id* as would be rails convention but is instead named *foo_bar_store_id*.  

If I was following the rails convention I would do the migration like this:

    class AddReferencesToPeople &lt; ActiveRecord::Migration
      def change
        add_reference :people, :store, index: true
      end
    end

However this will not work because the column name is not ***store_id*** but is ***foo_bar_store_id***.  So how do I specify that the foreign key name is just different, but still maintain index: true to maintain fast performance?

Rails Migration: add_reference to Table but Different Column Name For Foreign Key Than Rails Convention

I can&#39;t find the active record documenation page that has a list of all the data types.

Can someone help me out?


Where is the documentation page for ActiveRecord data types?

I have a `User` model and a `Task` model. I have not mentioned any relation between them while creating them. 

I need to establish that `User` `has_many` `Tasks` and a `Task` `belongs_to` `User` through a migration  

What would be the migration generation command for establishing that relationship?

has_many, belongs_to relation in active record migration rails 4

On Rails 4.0.0.rc1, Ruby 2.0.0, after I run a migration, I see the following error when I try to run a test through `rspec`:


&gt; /Users/peeja/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/activerecord-4.0.0.rc1/lib/active_record/migration.rb:376:in
&gt; `check_pending!&#39;: Migrations are pending; run &#39;rake db:migrate
&gt; RAILS_ENV=test&#39; to resolve this issue.
&gt; (ActiveRecord::PendingMigrationError)


That doesn&#39;t seem right. No one migrates their test database, do they? They `db:test:prepare` it, which—to be fair—I&#39;ve forgotten to do. So I run `rake db:test:prepare` and run my `rspec` command again…and see the same error.

If I actually `rake db:migrate RAILS_ENV=test`, the error does in fact go away.

What&#39;s going on? Is this new in Rails 4?

Why am I asked to run &#39;rake db:migrate RAILS_ENV=test&#39;?

I&#39;m in the process of adding Devise to an existing Rails app, with a Users table already defined. The devise generator pushed out the following migration:
        
    class AddDeviseToUsers &lt; ActiveRecord::Migration
      def self.up
        change_table(:users) do |t|
   
         ## Database authenticatable
         t.string :email,              :null =&gt; false, :default =&gt; &quot;&quot;
         t.string :encrypted_password, :null =&gt; false, :default =&gt; &quot;&quot;

         ## Recoverable
         t.string   :reset_password_token
         t.datetime :reset_password_sent_at
 
         ## Rememberable
         t.datetime :remember_created_at

         ## Trackable
         t.integer  :sign_in_count, :default =&gt; 0

         blah blah blah....

       end

       add_index :users, :email,                :unique =&gt; true
       add_index :users, :reset_password_token, :unique =&gt; true
     end

The downward migration isn&#39;t generated, and I&#39;m having a heck of a time removing those indexes. I&#39;m seeing different suggested notation in the documentation, and different suggestions online, but none of them seem to be working for me.  For example...

    def self.down
      change_table(:users) do |t|
        t.remove  :email
        t.remove  :encrypted_password
      
        t.remove  :reset_password_token

        blah blah blah...
      end
    
      remove_index :users, :email
      remove_index :users, :reset_password_token
    end

results in...

    An error has occurred, this and all later migrations canceled:

    Index name &#39;index_users_on_email&#39; on table &#39;users&#39; does not exist

which is odd, because if I check the database, sure enough, &#39;index_users_on_email&#39; is right there...  

I&#39;ve tried other variations, including

    remove_index :users, :column =&gt; :email

    remove_index :users, &#39;email&#39;

or:

    change_table(:users) do |t|
      t.remove_index :email
    end

...but no dice. I&#39;m running Rails 3.1.0, Ruby 1.9.2, rake 0.9.2.2, with Postgres.

The command that&#39;s letting me down is:

    bundle exec rake db:rollback STEP=1

after successfully apply the migration up. Any advice?

What&#39;s the correct syntax for remove_index in a Rails 3.1.0 migration?

It is easily possible to remove a column using rails migration.


    class SomeClass &lt; ActiveRecord::Migration
      def self.up
        remove_column :table_name, :column_name
      end
    end

I want to know if there is any way to remove a column from table using console.


How can i remove a column from table using rails console

I have a migration that removes a column:

    def change
      remove_column :foos, :bar, :boolean
    end

When I try to `rake db:rollback` that migration, I get the following error:

    remove_column is only reversible if given a type.

The [ActiveRecord::Migration][1] documentation says that the following is the signature for `remove_column`:

    remove_column(table_name, column_name, type, options)

So my type in this case should be `:boolean`, and I expect that migration to be reversible. What am I missing?

I can certainly break this out into an `up` and `down` migration to avoid this problem, but I&#39;d like to understand why the `change` syntax isn&#39;t working in this case.


  [1]: http://api.rubyonrails.org/classes/ActiveRecord/Migration.html

How do you make remove_column reversible?

After creating a migration file with `rails generate migration AddClientToUser` I can edit my migration file like so:

    class AddClientToUser &lt; ActiveRecord::Migration
      def self.up
        change_table :users do |t|
          t.references :client
        end
      end
    
      def self.down
        change_table :users do |t|
          t.remove :client_id
        end
      end
    end

Is this the correct way to reverse the reference column added in the migration?

Rails Migration with adding and removing reference

This questions stems from: https://stackoverflow.com/questions/11313872/how-to-link-form-after-creating-rails-join-table

I am creating the join table between my Product and Category Models.

What should the join table be named? categories_products or category_products or something else?

Rails naming convention for join table

I created a model ruby script/generate model Article (simple enuff)

Here is the migration file create_articles.rb:

    def self.up
      create_table :articles do |t|
        t.column :user_id, :integer
        t.column :title, :string
        t.column :synopsis, :text, :limit =&gt; 1000
        t.column :body, :text, :limit =&gt; 20000
        t.column :published, :boolean, :default =&gt; false
        t.column :created_at, :datetime
        t.column :updated_at, :datetime
        t.column :published_at, :datetime
        t.column :category_id, :integer
      end
    
    def self.down
      drop_table :articles
     end
    end

When I run the rake:db migrate command I receive an error rake aborted! &quot;Uninitialized constant CreateArticles.&quot;  

Does anyone know why this error keeps happening? 


When I run the rake:db migrate command I get an error &quot;Uninitialized constant CreateArticles&quot;

In Rails 2, will removing a column with a Rails migration also change/remove indexes associated with the column?  If not, and instead you have to also change/remove each index manually, shouldn&#39;t it instead be automated?

Thanks (from a Rails newbie)

Will removing a column with a Rails migration remove indexes associated with the column

I have a model &amp; a table which I no longer need in my App, I could leave them there but I would like to remove them to keep things tidy.

I&#39;m trying to figure out the best way to remove them with out messing around with my *migrations* &amp; *db/schema.rb* files &amp; any side effect it could have on my production environment, my app is on Heroku.  I&#39;m using PostgreSQL on both my local machine &amp; heroku.

So far I&#39;ve found two ways to do this but am not sure which is the best method/ rails way?

Method 1
--------

I thought about just going in to my database &amp; dropping the table &amp; then destroying the model.

    rails db
    DROP TABLE table_name
    \q
    rails destroy model model_name

If I do this what will happen to the migrations I have for this model/table?  I have two migrations for this model, a **timestamp_create_modelname** &amp; a add_attribute_to_table name.  

Also will this method update the *db/schema.rb* file?

When I push the App to Heroku I suspect the Model will be removed but the table will remain in place, is there a heroku command to drop a table.

Method Two
----------

Another way I read about was to generate a new migration to drop the table &amp; then destroy the model.

    rails generate migration drop_tablename

&amp; then update the below file:

db/migrate/timestamp_drop_tablename **(updated in response to Dan Wich&#39;s answer below)**

    class DropTablename &lt; ActiveRecord::Migration
      def up
        drop_table :tablename
      end
    
      def down
        create_table :tablename do |t|
          t.string :table_column
          t.references :anothertable

          t.timestamps        
        end
        add_index :tablenames, :anothertable_id
      end
    end

&amp; then in the terminal:

    rake db:migrate
    rails destroy model model_name
    rake db:migrate
    git add .
    git commit -m &quot;removed table/model_name&quot;
    git push heroku master
    heroku run rake db:migrate
    heroku restart

This seems to be the best method but what happens to the older migration files?  Will they remain &amp; update db/schema every time I run rake db:migrate only to be overridden by db/migrate/timestamp_drop_tablename?

I&#39;m happy to experiment with the second method but would like someone with someone with experience to weigh in &amp; tell me the rails ways for doing this.

What is the best way to drop a table &amp; remove a model in Rails 3?

I&#39;ve been doing the Rails tutorial found [here][1] and have been successful up to the point of having to migrate the Comments migration using **$ rails db:migrate**. Prior to this point, I&#39;ve been able to generate the Article model and migrate the Articles create migration with no issues. In between these two migrations, nothing has changed in my Gemfile, so I&#39;m not sure what it is Bundler is having an issue with. 

Here are the errors, followed by the full command-line output, along with my Gemfile and schema.rb:

    Gem::LoadError: can&#39;t activate pg (~&gt; 0.18), already activated pg-1.0.0.
    
    Gem::LoadError: Specified &#39;postgresql&#39; for database adapter, but the gem is not loaded. Add `gem &#39;pg&#39;` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord).

**Full command-line output**

    xxx:gangelo: ~/dev/rails/test/blog (master*) ☠  rbenv exec rails db:migrate
    rails aborted!
    Gem::LoadError: Specified &#39;postgresql&#39; for database adapter, but the gem is not loaded. Add `gem &#39;pg&#39;` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord).
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:188:in `rescue in spec&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:185:in `spec&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:880:in `establish_connection&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_handling.rb:58:in `establish_connection&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:124:in `block (2 levels) in &lt;class:Railtie&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `instance_eval&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `block in execute_hook&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:60:in `with_execution_control&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:65:in `execute_hook&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:50:in `block in run_load_hooks&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `each&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `run_load_hooks&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:326:in `&lt;module:ActiveRecord&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:25:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:6:in `&lt;class:MySQLDatabaseTasks&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:3:in `&lt;module:Tasks&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:2:in `&lt;module:ActiveRecord&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:1:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:74:in `&lt;module:DatabaseTasks&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:35:in `&lt;module:Tasks&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:2:in `&lt;module:ActiveRecord&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:1:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:34:in `block (3 levels) in &lt;class:Railtie&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:21:in `block in perform&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:18:in `perform&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/command.rb:46:in `invoke&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands.rb:16:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/bin/rails:9:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/bin/rails:9:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `load&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `call&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/command.rb:7:in `call&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client.rb:30:in `run&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/bin/spring:49:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `load&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/bin/spring:15:in `&lt;top (required)&gt;&#39;
    bin/rails:3:in `load&#39;
    bin/rails:3:in `&lt;main&gt;&#39;
    
    Caused by:
    Gem::LoadError: can&#39;t activate pg (~&gt; 0.18), already activated pg-1.0.0. Make sure all dependencies are added to Gemfile.
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/postgresql_adapter.rb:2:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:186:in `spec&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:880:in `establish_connection&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_handling.rb:58:in `establish_connection&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:124:in `block (2 levels) in &lt;class:Railtie&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `instance_eval&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `block in execute_hook&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:60:in `with_execution_control&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:65:in `execute_hook&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:50:in `block in run_load_hooks&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `each&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `run_load_hooks&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:326:in `&lt;module:ActiveRecord&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:25:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:6:in `&lt;class:MySQLDatabaseTasks&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:3:in `&lt;module:Tasks&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:2:in `&lt;module:ActiveRecord&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:1:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:74:in `&lt;module:DatabaseTasks&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:35:in `&lt;module:Tasks&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:2:in `&lt;module:ActiveRecord&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:1:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:34:in `block (3 levels) in &lt;class:Railtie&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:21:in `block in perform&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:18:in `perform&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/command.rb:46:in `invoke&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands.rb:16:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/bin/rails:9:in `require&#39;
    /Users/gangelo/dev/rails/test/blog/bin/rails:9:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `load&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `call&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/command.rb:7:in `call&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client.rb:30:in `run&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/bin/spring:49:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `load&#39;
    /Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `&lt;top (required)&gt;&#39;
    /Users/gangelo/dev/rails/test/blog/bin/spring:15:in `&lt;top (required)&gt;&#39;
    bin/rails:3:in `load&#39;
    bin/rails:3:in `&lt;main&gt;&#39;
    Tasks: TOP =&gt; db:migrate =&gt; db:load_config
    (See full trace by running task with --trace)

**Gemfile**

    source &#39;https://rubygems.org&#39;
    
    ruby &#39;2.3.1&#39;
    
    git_source(:github) do |repo_name|
      repo_name = &quot;#{repo_name}/#{repo_name}&quot; unless repo_name.include?(&quot;/&quot;)
      &quot;https://github.com/#{repo_name}.git&quot;
    end
    
    
    # Bundle edge Rails instead: gem &#39;rails&#39;, github: &#39;rails/rails&#39;
    gem &#39;rails&#39;, &#39;~&gt; 5.1.4&#39;
    
    # Use sqlite3 as the database for Active Record
    # gem &#39;sqlite3&#39;
    
    # Use postgres as the database for Active Record
    gem &#39;pg&#39;
    
    # Use Puma as the app server
    gem &#39;puma&#39;, &#39;~&gt; 3.7&#39;
    # Use SCSS for stylesheets
    gem &#39;sass-rails&#39;, &#39;~&gt; 5.0&#39;
    # Use Uglifier as compressor for JavaScript assets
    gem &#39;uglifier&#39;, &#39;&gt;= 1.3.0&#39;
    # See https://github.com/rails/execjs#readme for more supported runtimes
    # gem &#39;therubyracer&#39;, platforms: :ruby
    
    # Use CoffeeScript for .coffee assets and views
    gem &#39;coffee-rails&#39;, &#39;~&gt; 4.2&#39;
    # Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
    gem &#39;turbolinks&#39;, &#39;~&gt; 5&#39;
    # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
    gem &#39;jbuilder&#39;, &#39;~&gt; 2.5&#39;
    # Use Redis adapter to run Action Cable in production
    # gem &#39;redis&#39;, &#39;~&gt; 3.0&#39;
    # Use ActiveModel has_secure_password
    # gem &#39;bcrypt&#39;, &#39;~&gt; 3.1.7&#39;
    
    # Use Capistrano for deployment
    # gem &#39;capistrano-rails&#39;, group: :development
    
    group :development, :test do
      # Call &#39;byebug&#39; anywhere in the code to stop execution and get a debugger console
      gem &#39;byebug&#39;, platforms: [:mri, :mingw, :x64_mingw]
      # Adds support for Capybara system testing and selenium driver
      gem &#39;capybara&#39;, &#39;~&gt; 2.13&#39;
      gem &#39;selenium-webdriver&#39;
    end
    
    # gma - start
    group :development, :test do
      gem &#39;rspec-rails&#39;, &#39;~&gt; 3.5&#39;, &#39;&gt;= 3.5.2&#39;
      gem &#39;rspec-activemodel-mocks&#39;, &#39;~&gt; 1.0&#39;, &#39;&gt;= 1.0.3&#39;
      gem &#39;shoulda-matchers&#39;, &#39;~&gt; 3.1&#39;, &#39;&gt;= 3.1.1&#39;
      gem &#39;factory_bot_rails&#39;, &#39;~&gt; 4.8&#39;, &#39;&gt;= 4.8.2&#39;
      gem &#39;ffaker&#39;, &#39;~&gt; 2.2&#39;
      # gem &#39;timecop&#39;, &#39;~&gt; 0.8.1&#39;
    end
    # gma - end
    
    group :development do
      # Access an IRB console on exception pages or by using &lt;%= console %&gt; anywhere in the code.
      gem &#39;web-console&#39;, &#39;&gt;= 3.3.0&#39;
      gem &#39;listen&#39;, &#39;&gt;= 3.0.5&#39;, &#39;&lt; 3.2&#39;
      # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
      gem &#39;spring&#39;
      gem &#39;spring-watcher-listen&#39;, &#39;~&gt; 2.0.0&#39;
    end
    
    # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
    gem &#39;tzinfo-data&#39;, platforms: [:mingw, :mswin, :x64_mingw, :jruby]

  
**Schema.rb**

    ActiveRecord::Schema.define(version: 20180110153949) do
      # These are extensions that must be enabled in order to support this database
      enable_extension &quot;plpgsql&quot;
    
      create_table &quot;articles&quot;, force: :cascade do |t|
        t.string &quot;title&quot;
        t.text &quot;text&quot;
        t.datetime &quot;created_at&quot;, null: false
        t.datetime &quot;updated_at&quot;, null: false
      end
    end

**Migration file**

    class CreateComments &lt; ActiveRecord::Migration[5.1]
      def change
        create_table :comments do |t|
          t.string :commenter
          t.text :body
          t.references :article, foreign_key: true
    
          t.timestamps
        end
      end
    end


[1]: http://guides.rubyonrails.org/getting_started.html


Gem::LoadError: can&#39;t activate pg (~&gt; 0.18), already activated pg-1.0.0

I have been switching between branches in a project and each of them have different migrations... This is the scenario:


&gt; $ rake db:migrate:status

     Status   Migration ID    Migration Name
    --------------------------------------------------
       ...
       up     20130307154128  Change columns in traffic capture
       up     20130311155109  Remove log settings
       up     20130311160901  Remove log alarm table
       up     20130320144219  ********** NO FILE **********
       up     20130320161939  ********** NO FILE **********
       up     20130320184628  ********** NO FILE **********
       up     20130322004817  Add replicate to root settings
       up     20130403190042  ********** NO FILE **********
       up     20130403195300  ********** NO FILE **********
       up     20130403214000  ********** NO FILE **********
       up     20130405164752  Fix ap hostnames
       up     20130410194222  ********** NO FILE **********


The problem is `rake db:rollback` don&#39;t work at all because of the missing files...

What should I do to be able to rollback again and get rid of the NO FILE messages?

Btw, `rake db:reset` or `rake db:drop` are not an option, I cannot lose data from other tables...

What is the best way to resolve Rails orphaned migrations?

Is the following correct?

     change_column :tablename, :fieldname, :limit =&gt; null

In a rails migration, how can you remove the limit of a field

Given the following `schema.rb`:

      create_table &quot;people&quot;, force: true do |t|
        t.string   &quot;name&quot;,  null: false
        t.integer  &quot;age&quot;
        t.integer  &quot;height&quot;
        t.string   &quot;email&quot;
        t.boolean  &quot;married&quot;,  default: false
        t.text     &quot;bio&quot;
        t.integer  &quot;fav_number&quot;
        t.decimal  &quot;lucky_num&quot;,  precision: 2, scale: 2
        t.datetime &quot;birthday&quot;
        t.datetime &quot;created_at&quot;
        t.datetime &quot;updated_at&quot;
      end

I&#39;d like to remove the `name` default value of `null: false`. I&#39;ve tried running a separate migration with `change_column_default`, but that had no impact on `schema.rb`. Any suggestions?

All Rails Migrations Solutions on Gang of Coders

Total of 27 Rails Migrations Solutions