rails migration runs on local Postgresql but fails on prod

Question

In short, dropping, creating, and running migrate on the local Postgres instance will work any number of times for creating a working database for my app, but the same technique on Heroku's prod always produces:

heroku run rake db:migrate
Running `rake db:migrate` attached to terminal... up, run.9674
PG::UndefinedTable: ERROR:  relation "mytable" does not exist
LINE 5:                WHERE a.attrelid = '"mytable"'::regclass
                                          ^
:               SELECT a.attname, format_type(a.atttypid, a.atttypmod),
                     pg_get_expr(d.adbin, d.adrelid), a.attnotnull, a.atttypid, a.atttypmod
                FROM pg_attribute a LEFT JOIN pg_attrdef d
                  ON a.attrelid = d.adrelid AND a.attnum = d.adnum
               WHERE a.attrelid = '"mytable"'::regclass
                 AND a.attnum > 0 AND NOT a.attisdropped
               ORDER BY a.attnum

rake aborted!
PG::UndefinedTable: ERROR:  relation "mytable" does not exist
LINE 5:                WHERE a.attrelid = '"mytable"'::regclass
                                          ^
:               SELECT a.attname, format_type(a.atttypid, a.atttypmod),
                     pg_get_expr(d.adbin, d.adrelid), a.attnotnull, a.atttypid, a.atttypmod
                FROM pg_attribute a LEFT JOIN pg_attrdef d
                  ON a.attrelid = d.adrelid AND a.attnum = d.adnum
               WHERE a.attrelid = '"mytable"'::regclass
                 AND a.attnum > 0 AND NOT a.attisdropped
               ORDER BY a.attnum

EDIT: see bottom of question for clue on controller getting accessed during migrate.

This is what works locally:

rake db:drop
rake db:create
rake db:migrate

I have

confirmed that Heroku's db is blank before migration by doing heroku pg:psql and then \dt to verify 0 tables exist.
tried heroku pg:reset DATABASE before the migrate
confirmed both local and prod Postgres is version 9.2.4
tried renaming the "mytable" migration file in db/migrate to have the earliest timestamp so as to get run first

This is a pretty simple app so it's very frustrating that something basic like creating a db from scratch keeps failing. Any ideas?

"mytable" migration:

class CreateMytable < ActiveRecord::Migration
  def change
    create_table :mytable do |t|
      t.string :codes
      t.string :name

      t.timestamps
    end
  end
end

likely referecing migration:

class CreateTable2 < ActiveRecord::Migration
  def change
    create_table :table2 do |t|
      t.references :a, index: true
      t.references :b, index: true
      t.string :c
      t.string :d

      t.timestamps
    end
  end
end

EDIT: noticed a clue when running db:migrate with --trace. The top of the stack trace below error shows a controller error?? Why is a controller getting involved with a migration?

/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql_adapter.rb:768:in `exec'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql_adapter.rb:768:in `exec_no_cache'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:138:in `block in exec_query'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:425:in `block in log'
/app/vendor/bundle/ruby/2.0.0/gems/activesupport-4.0.0/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:420:in `log'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:137:in `exec_query'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql_adapter.rb:915:in `column_definitions'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql/schema_statements.rb:174:in `columns'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/schema_cache.rb:114:in `block in prepare_default_proc'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/schema_cache.rb:56:in `yield'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/connection_adapters/schema_cache.rb:56:in `columns'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/model_schema.rb:208:in `columns'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/model_schema.rb:242:in `column_defaults'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/locking/optimistic.rb:169:in `column_defaults'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/core.rb:181:in `initialize'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/inheritance.rb:27:in `new'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.0.0/lib/active_record/inheritance.rb:27:in `new'
/app/app/controllers/home_controller.rb:7:in `<class:HomeController>'

The line 7 in question contains a call to Mytable.new(... . How is it controller code is coming into scope during a db:migrate?

Can you post this migration and the one that includes "mytable"? — steakchaser
– steakchaser, Commented Sep 7, 2013 at 23:22
Added "mytable" migration, but I don't know how to determine what other migration is running when the error occurs. — Josh Diehl
– Josh Diehl, Commented Sep 7, 2013 at 23:31
I'm actually not sure... I would try some of the approaches listed in here (including removing your app entirely). stackoverflow.com/questions/5450930/… — steakchaser
– steakchaser, Commented Sep 7, 2013 at 23:51
Can you run the migrate with --trace? This should give you the migration that's running when it fails. — Jason N
– Jason N, Commented Sep 8, 2013 at 0:07
that make sense now thanks :) I just came across this relating to the controller code being loaded during a migration. You may be running into the same bug, github.com/activescaffold/active_scaffold/issues/131. A quick test would be to add config.cache_classes = false to production.rb. — Jason N
– Jason N, Commented Sep 8, 2013 at 0:32

Josh Diehl · Accepted Answer · 2013-09-08 01:59:28Z

1

This was somehow being caused by setting a class variable in a Rails controller that referenced the "mytable" class. So basically this:

 class HomeController < ApplicationController
  @@data = {MyTable.new(...

Moving this inside of a controller method and making it a non-class variable fixed the problem( I didn't isolate whether it was the class var aspect or location right below class def that was the cause).

I still don't understand why controller code was a factor in a db migrate. I'd be interested to hear if this is something I was doing wrong, or a bug in rake, rails, or something else. Only happened in Heroku production, Rails 4.0.0

answered Sep 8, 2013 at 1:59

Josh Diehl

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1 Comment

Jason N Over a year ago

Josh, running a migration loads all the app code and because you had this this in a class variable it was loaded when the app code was initially loaded (because the class itself was run through the interpreter), causing an error when the db table didn't exist. You could probably comment this line out to run the migrations and then uncomment it if you wanted to keep it. Either way, interesting failure!

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