db:migrate hangs on simple migration

Question

I am using PostgreSQL, Rails 3.1.3 and Ruby 1.9.3. I am struggling to use db:migrate as outlined here.

This is what I am seeing in the terminal:

funkdified@funkdified-laptop:~/railsprojects/hartl$ bundle exec rake db:migrate --trace 
** Invoke db:migrate (first_time) 
** Invoke environment (first_time) 
** Execute environment 
** Invoke db:load_config (first_time) 
** Invoke rails_env (first_time) 
** Execute rails_env 
** Execute db:load_config 
** Execute db:migrate 
== AddEmailUniquenessIndex: migrating ======================================== 
-- add_index(:users, :email, {:unique=>true})

and then the code hangs at this point. Any ideas why?

From: development.log

[1m[36m (0.1ms)[0m [1mSHOW search_path[0m 
[1m[35m (0.5ms)[0m SELECT "schema_migrations"."version" FROM "schema_migrations"
Migrating to CreateUsers (20120124022843) 
Migrating to AddEmailUniquenessIndex (20120124093922) 
[1m[36m (0.1ms)[0m [1mBEGIN[0m 
[1m[35m (3.6ms)[0m SELECT distinct i.relname, d.indisunique, d.indkey, t.oid 
FROM pg_class t 
INNER JOIN pg_index d ON t.oid = d.indrelid 
INNER JOIN pg_class i ON d.indexrelid = i.oid 
WHERE i.relkind = 'i' 
AND d.indisprimary = 'f' 
AND t.relname = 'users' 
AND i.relnamespace IN (SELECT oid FROM pg_namespace WHERE nspname = ANY (current_schemas(false)) ) 
ORDER BY i.relname

Answer 1

I just had a similar problem, where a very simple migration was stalling for no apparent reason. I believe the problem has to do with not being able to get a database connection. I exited a rails console session that I had open in another terminal and then the migration immediately finished with no problems.

Answer 2

I just made two migrations. The first one created a new table, the second one removed fields from an existing table. The second migration was hanging, and the reason turned out to be a rails console session (rails console --sandbox) running in another terminal windows.

Answer 3

I had the same issue and after trying a bunch of solutions what worked was...shutting down all of my terminal sessions, restarting the computer, and trying again. Sometimes it's just power cycle magic.