add_column ignores index: true

[collimarco]

Using Rails 4.2.0 the index: true part in the following statement is completely ignored:

add_column :my_table, :my_column, :boolean, index: true

This happens for any type of column (e.g. boolean, string).

To reproduce this issue just create a table:

class CreateExamples < ActiveRecord::Migration
  def change
    create_table :examples
  end
end

Then add:

class AddSomethingToExamples < ActiveRecord::Migration
  def change
    add_column :examples, :something, :string, index: true
  end
end

Run the migrations. Then check schema.rbor directly the database and you won't find any index.

The documentation says:

See ActiveRecord::ConnectionAdapters::TableDefinition#column for details of the options you can use.

:index - Create an index for the column. Can be either true or an options hash.

[rafaelfranca]

This is a documentation problem. Could you send a PR?

[collimarco]

What's wrong exactly with the documentation?

Is it the whole statement?

See ActiveRecord::ConnectionAdapters::TableDefinition#column for details of the options you can use.

Or only a part of it?

Furthermore I find it useful to be able to pass options (such as index: true) to add_column. Are you sure that is only documentation that needs to be fixed and not the code?

[rafaelfranca]

The whole statement. add_column don't call TableDefinition#column, its call AlterTable#add_column and this function don't accept all the options of TableDefinition#column.

The code can be changed, yes, bug only on the master branch. Meanwhile the stable branch will be with the wrong documentation so it is better to fix the documentation first and we can change the code later.

[collimarco]

Ok, sure! As you say the index option is passed up to this method, where, indeed, is lost.

[senny]

@collimarco I moved the documentation of common options to add_column. The column method now only documents the additional behavior. That should prevent further confusion. Thank you for reporting 💛

[wagenet]

https://edgeguides.rubyonrails.org/active_record_migrations.html#column-modifiers still implies that this works.

[dogweather]

@wagenet I'd say it's even more than that: The Guide affirmatively states that index is a valid option:

index Adds an index for the column.

@rafaelfranca I'd like to work on removing silent failures. Here, if the programmer uses an unknown or invalid option (like index), the code can help. It could log at the WARN level about the ignored option, or raise an error.

Would a PR for this be welcomed?