Rails 5 db migration: how to fix ActiveRecord::ConcurrentMigrationError

Question

A previous rake db:rollback stalled. Now when attempting a new migration we get the following error:

rake aborted!
ActiveRecord::ConcurrentMigrationError: 

         


        

Answer 1

For me it was resolved in this way:

Select advisory locks:

SELECT pid, locktype, mode FROM pg_locks WHERE locktype = 'advisory';

SELECT pg_terminate_backend();