How do I solve "index unique_schema_migrations already exists" in Rails?
migration, ruby, ruby-on-rails
Solution
In SQLite, index name uniqueness is enforced at the database level. In MySQL, uniqueness is enforced only at the table level. That's why your migrations work in the latter and not the former: you have two indexes with the same name on different tables.
Rename the index, or find and rename the other `unique_schema_migrations` index, and your migrations should work.
Problem
Running `rake db:migrate` followed by `rake test:units` yields the following: ``` rake test:functionals (in /projects/my_project) rake aborted! SQLite3::SQLException: index unique_schema_migrations already exists: CREATE UNIQUE INDEX "unique_schema_migrations" ON "ts_schema_migrations" ("version") ``` The relevant part of `db/schema.rb` is as follows: ``` create_table "ts_schema_migrations", :id => false, :force => true do |t| t.string "version", :null => false end add_index "ts_schema_migrations", ["version"], :name => "unique_schema_migrations", :unique => true ``` I'm not manually changing this index anywhere, and I'm using Rails' default SQLite3 adapter with a brand new database. (That is, running `rm db/*sqlite3` before `rake db:migrate` doesn't help.) Is the `test:units` task perhaps trying to re-load the schema? If so, why? Shouldn't it recognize the schema is already up to date?