What's the correct syntax for remove_index in a Rails 3.1.0 migration?

Question

I\'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:

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Answer 1

Here is my full run of this(in Rails 5):

I have team_id as an index in table vendors. I no longer need this relation. To get rid of it. Did the following:

1) create the migration.

  $ rails generate migration RemoveTeam_idFromVendor team_id:integer

2) Running the migration, give me this error. And that is because vendor table has rows whose foreign key references the primary key value of the team table

== 20170727202815 RemoveTeamIdFromVendor: migrating ===========================
-- remove_column(:vendors, :team_id, :integer)
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:

SQLite3::ConstraintException: FOREIGN KEY constraint failed: DROP TABLE "vendors"

3) To solve this and get the migration running, I did the following(Note: i am in dev):

$ rake db:drop


Dropped database 'db/development.sqlite3'
Dropped database 'db/test.sqlite3'


$ rake db:create
Created database 'db/development.sqlite3'
Created database 'db/test.sqlite3'

$ rake db:migrate
~
~
~

== 20170727202815 RemoveTeamIdFromVendor: migrating ===========================
-- remove_column(:vendors, :team_id, :integer)
   -> 0.0185s
== 20170727202815 RemoveTeamIdFromVendor: migrated (0.0185s) ==================