[BUG] delete_all using wrong database connection when executing on relation

Context

Using Rails 3.0.3 and Ruby 1.9.2

In one rails project i'm using multiple database connections (code below) and different adapters (mysql and pq).
Connection to RedMine using Mysql adapter
Connection to main database using PostgreSQL adapter

Problem

When I fetching all specification for project it works fine

ruby-1.9.2-p0 > project.specifications
 => [#<RedMine::SpecificationCache id: 1, project_id: 45, version_id: 71, developer_id: nil, status: "@_todo", estimation: nil, tags: "@mapa @__kb_articles", scenario_title: "Scenario 1", feature_title: "Feature 1", feature_hash_id: nil>, #<RedMine::SpecificationCache id: 3, project_id: 45, version_id: 71, developer_id: nil, status: "@_backlog", estimation: nil, tags: "@map @__kb_articles", scenario_title: "Scenario 1", feature_title: "Feature 2", feature_hash_id: nil>, #<RedMine::SpecificationCache id: 4, project_id: 45, version_id: 71, developer_id: 0, status: "@_done", estimation: nil, tags: "@__kb_articles @test @map @onet", scenario_title: "Scenario 2", feature_title: "Feature 1", feature_hash_id: nil>]

but when i try to delete all specification that is related to particular project, sql is executed on main database instead of using connection to RedMine database. ( and if this could be big problem in production - of course in some circumstances )

ruby-1.9.2-p0 > project.specifications.delete_all
ActiveRecord::StatementInvalid: PGError: ERROR:  relation "specification_cache" does not exist
LINE 4:              WHERE a.attrelid = '"specification_cache"'::reg...
                                        ^
:             SELECT a.attname, format_type(a.atttypid, a.atttypmod), d.adsrc, a.attnotnull
              FROM pg_attribute a LEFT JOIN pg_attrdef d
                ON a.attrelid = d.adrelid AND a.attnum = d.adnum
             WHERE a.attrelid = '"specification_cache"'::regclass
               AND a.attnum > 0 AND NOT a.attisdropped
             ORDER BY a.attnum

    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/connection_adapters/abstract_adapter.rb:202:in `rescue in log'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/connection_adapters/abstract_adapter.rb:194:in `log'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/connection_adapters/postgresql_adapter.rb:483:in `query'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/connection_adapters/postgresql_adapter.rb:1015:in `column_definitions'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/connection_adapters/postgresql_adapter.rb:662:in `columns'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/arel-2.0.4/lib/arel/table.rb:93:in `columns'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/arel-2.0.4/lib/arel/table.rb:100:in `[]'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/associations/has_many_association.rb:78:in `delete_records'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/associations/association_collection.rb:222:in `block in delete'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/associations/association_collection.rb:525:in `block in remove_records'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/associations/association_collection.rb:158:in `block in transaction'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/connection_adapters/abstract/database_statements.rb:139:in `transaction'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/transactions.rb:204:in `transaction'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/associations/association_collection.rb:157:in `transaction'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/associations/association_collection.rb:522:in `remove_records'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/associations/association_collection.rb:221:in `delete'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/activerecord-3.0.3/lib/active_record/associations/association_collection.rb:167:in `delete_all'
    from (irb):7
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/railties-3.0.3/lib/rails/commands/console.rb:44:in `start'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/railties-3.0.3/lib/rails/commands/console.rb:8:in `start'
    from /home/mc/.rvm/gems/ruby-1.9.2-p0@selleo-dashboard/gems/railties-3.0.3/lib/rails/commands.rb:23:in `<top (required)>'
    from script/rails:6:in `require'

I'm not sure but maybe AR is setting wrong engine on Arel, but not able to confirm or deny this

Source Code

class Abstract::RedMine < ActiveRecord::Base
  self.abstract_class = true
  establish_connection("redmine_#{Rails.env}")

  private

  def self.instantiate(record)
    (record[self.inheritance_column] = "RedMine::"+record[self.inheritance_column]) if record[self.inheritance_column]
    super
  end
end

class RedMine::Project < Abstract::RedMine
  # ...
  has_many :specifications, :class_name => 'RedMine::SpecificationCache'
  # ...
end

class RedMine::SpecificationCache < Abstract::RedMine
  set_table_name 'specification_cache'
end