rake task to load fixtures with pg/heroku issue

Author: xuorig

lib/tasks/load_fixtures.rake

@@ -0,0 +1,50 @@
+# weird issue with heroku + postgres referential integrity
+# http://pvcarrera.github.io/general/2016/02/15/rails-fixtures-and-referencial-integrity.html
+
+namespace :db do
+  desc 'Reset and populate sample data'
+  task load_swapi_fixtures: [:reset, :drop_constraints, 'fixtures:load', :create_constraints] do
+    puts 'Fixtures loaded in the database'
+  end
+
+  desc 'Remove all database constraints'
+  task drop_constraints: [:environment, :create_constraints_script, :drop_constraints_script] do
+    ActiveRecord::Base.connection.execute(IO.read('tmp/drop_constraints.sql'))
+    puts 'Constraints dropped'
+  end
+
+  desc 'Recreate database constraints'
+  task create_constraints: [:environment, :create_constraints_script, :drop_constraints_script] do
+    ActiveRecord::Base.connection.execute(IO.read('tmp/create_constraints.sql'))
+    puts 'Constraints recreated'
+  end
+
+  file drop_constraints_script: :environment do
+    query = (<<-SQL)
+      SELECT 'ALTER TABLE "'||nspname||'"."'||relname||'" DROP CONSTRAINT "'||conname||'";'
+        FROM pg_constraint
+        INNER JOIN pg_class ON conrelid=pg_class.oid
+        INNER JOIN pg_namespace ON pg_namespace.oid=pg_class.relnamespace
+        ORDER BY CASE WHEN contype='f' THEN 0 ELSE 1 END,contype,nspname,relname,conname
+    SQL
+    array_to_file(ActiveRecord::Base.connection.execute(query), 'drop_constraints.sql')
+  end
+
+  file create_constraints_script: :environment do
+    query = (<<-SQL)
+      SELECT 'ALTER TABLE "'||nspname||'"."'||relname||'" ADD CONSTRAINT "'||conname||'" '|| pg_get_constraintdef(pg_constraint.oid)||';'
+       FROM pg_constraint
+       INNER JOIN pg_class ON conrelid=pg_class.oid
+       INNER JOIN pg_namespace ON pg_namespace.oid=pg_class.relnamespace
+       ORDER BY CASE WHEN contype='f' THEN 0 ELSE 1 END DESC,contype DESC,nspname DESC,relname DESC,conname DESC
+    SQL
+    array_to_file(ActiveRecord::Base.connection.execute(query), 'create_constraints.sql')
+  end
+
+  def array_to_file(array, file_name)
+    Dir.mkdir('tmp') unless File.exist?('tmp')
+    File.open("tmp/#{file_name}", 'w+') do |f|
+      f.puts(array.values.flatten)
+    end
+  end
+end