script generate migration remove foreign key constraints; cut and paste in up/down/change block rails; uses schema_plus_foreign_key "4-argument" syntax https://github.com/SchemaPlus/schema_plus_foreign_keys/blob/affa91c1a508dae2ff8bb7be9e3ed4731106ae1e/lib/schema_plus/foreign_keys/active_record/connection_adapters/abstract_adapter.rb#L31

migration-remove-foreign-key-constraints.rb

sql = "SELECT 
  TABLE_NAME,COLUMN_NAME,CONSTRAINT_NAME, REFERENCED_TABLE_NAME, REFERENCED_COLUMN_NAME
FROM
  INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE REFERENCED_TABLE_SCHEMA = 'awesome_db'"
x = ActiveRecord::Base.connection.execute(sql)

# remove constraints
z = x.map {|y| 
  "remove_foreign_key :#{y[0]}, column: '#{y[1]}', name: '#{y[2]}'\n" +
  "add_foreign_key    '#{y[0]}', ['#{y[1]}'], '#{y[3]}', ['#{y[4]}'], on_update: :no_action, on_delete: :no_action, name: '#{y[2]}'"
};nil
puts z.join("\n\n");nil

# reverse to default :restrict
z = x.map {|y| 
  "remove_foreign_key :#{y[0]}, column: '#{y[1]}', name: '#{y[2]}'\n" +
  "add_foreign_key    '#{y[0]}', ['#{y[1]}'], '#{y[3]}', ['#{y[4]}'], on_update: :restrict, on_delete: :restrict, name: '#{y[2]}'"
};nil
puts z.join("\n\n");nil