# Dynamic connection **URL:** \ **Category:** Rails\ **Created:** [May 9, 2007, 2:58pm UTC](https://www.ruby-forum.com/t/dynamic-connection/103705 "2007-05-09T14:58:31Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![bazzel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/76d3ee/32.png) [@bazzel](https://www.ruby-forum.com/u/bazzel)\ **Post date:** [May 9, 2007, 2:58pm UTC](https://www.ruby-forum.com/t/dynamic-connection/103705/1 "2007-05-09T14:58:31Z")
Hello all, In my Rails app I have a model which I want to use to maintain records in several tables (identical structure) in multiple databases. Is there a way to use establish\_connection and set\_table\_name in a dynamic way? ---
**Author:** ![bazzel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/76d3ee/32.png) [@bazzel](https://www.ruby-forum.com/u/bazzel)\ **Post date:** [May 9, 2007, 3:33pm UTC](https://www.ruby-forum.com/t/dynamic-connection/103705/2 "2007-05-09T15:33:42Z")
Yes, there is. establish\_connection and _not_ set\_table\_name is the answer. I’ve been down both routes and establish\_connection is much lighter on the necessary code than set\_table\_name. RSL ---
**Author:** ![bazzel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/76d3ee/32.png) [@bazzel](https://www.ruby-forum.com/u/bazzel)\ **Post date:** [May 9, 2007, 4:28pm UTC](https://www.ruby-forum.com/t/dynamic-connection/103705/3 "2007-05-09T16:28:32Z")
Russell N. wrote: > Yes, there is. establish\_connection and _not_ set\_table\_name is the > answer. > I’ve been down both routes and establish\_connection is much lighter on > the > necessary code than set\_table\_name. > > RSL Hi RSL, Thanks for answering. However, I think I need both set\_table\_name and establish\_connection I want to access multiple tables on multiple databases. Maybe I can overload the ActiveRecord class methods create, save, etc. by defining extra parameters for both connection and table\_name: ` def self.create(attributes, connection, table_name) set_table_name = table_name establish_connection connection super(attributes) end ` but I haven’t tried this appraach yet. ---
**Author:** ![bazzel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/76d3ee/32.png) [@bazzel](https://www.ruby-forum.com/u/bazzel)\ **Post date:** [May 10, 2007, 10:13am UTC](https://www.ruby-forum.com/t/dynamic-connection/103705/4 "2007-05-10T10:13:37Z")
I figured out that it’s actually pretty easy to set connection and tablename dynamically by using establish\_connection and set\_table\_name for my model only: … Site.establish\_connection some\_method Site.set\_table\_name another\_method Site.create (or whatever class method) In my situation I want to update several MSSQL records on several servers. The default database is mySQL. However… since I use the RedHill lpugin ([http://www.redhillonrails.org/#redhillonrails\_core](http://www.redhillonrails.org/#redhillonrails_core)) it seems that there is a conflict when I try to create or update on MSSQL when my default connection connects to mySQL: NoMethodError: undefined method `[]=' for # from c:/DEV/ruby/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/active_record/connection_adapters/sqlserver_adapter.rb:439:in `indexes’ from ./script/…/config/…/config/…/vendor/plugins/redhillonrails\_core/lib/red\_hill\_consulting/core/active\_record/base.rb:42:in `indexes' from ./script/../config/../config/../vendor/plugins/redhillonrails_core/lib/red_hill_consulting/core/active_record/base.rb:27:in `columns’ from c:/DEV/ruby/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/active\_record/base.rb:776:in `column_names' from c:/DEV/ruby/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/active_record/base.rb:789:in `column\_methods\_hash’ from c:/DEV/ruby/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/active\_record/base.rb:1263:in `all_attributes_exists?' from (irb):9:in `all?’ from c:/DEV/ruby/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/active\_record/base.rb:1263:in `each' from c:/DEV/ruby/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/active_record/base.rb:1263:in `all?’ from c:/DEV/ruby/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/active\_record/base.rb:1263:in `all_attributes_exists?' from c:/DEV/ruby/lib/ruby/gems/1.8/gems/activerecord-1.15.2/lib/active_record/base.rb:1197:in `method\_missing’ from (irb):9 The story continues, but thanks for the reply! Patrick ---
**Author:** ![bazzel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/76d3ee/32.png) [@bazzel](https://www.ruby-forum.com/u/bazzel)\ **Post date:** [May 9, 2007, 4:41pm UTC](https://www.ruby-forum.com/t/dynamic-connection/103705/5 "2007-05-09T16:41:45Z")
Here’s what I did. Site model is in the default db and contains a db\_name attribute which holds the name of the db for that site. In Site… DB\_PREFIX = “whatever\_” def ensure\_connection [Attachment, Document, Category, Tag].each do |klass| unless ActiveRecord::Base.configurations.has\_key? db\_name config = ActiveRecord::Base.configurations[RAILS\_ENV] ActiveRecord::Base.configurations[db\_name] = { :adapter =\> “mysql”, :host =\> config[“host”], :username =\> config[“username”], :password =\> config[“password”], :database =\> “#{DB\_PREFIX}#{db\_name}” } end [Attachment, Category, Comment, Document, Tag, Source].each do |model| if model.connection.config[:database] != “#{DB\_PREFIX}#{db\_name}” model.establish\_connection db\_name # You have to do this manually… model.connection.logger = RAILS\_DEFAULT\_LOGGER end end end end and in my controllers that need to access that data just create a before\_filter which calls Site#ensure\_connections. Unless you’re on to something I wasn’t set\_table\_name is more trouble than it’s worth. Hope that helps. RSL