Merge pull request rails#412 from yui-knk/remove_not_used_codes

Delete not used codes

lib/arel/visitors.rb

@@ -14,28 +14,5 @@
 
 module Arel
   module Visitors
-    VISITORS = {
-      'postgresql'      => Arel::Visitors::PostgreSQL,
-      'mysql'           => Arel::Visitors::MySQL,
-      'mysql2'          => Arel::Visitors::MySQL,
-      'mssql'           => Arel::Visitors::MSSQL,
-      'sqlserver'       => Arel::Visitors::MSSQL,
-      'oracle_enhanced' => Arel::Visitors::Oracle,
-      'sqlite'          => Arel::Visitors::SQLite,
-      'sqlite3'         => Arel::Visitors::SQLite,
-      'ibm_db'          => Arel::Visitors::IBM_DB,
-      'informix'        => Arel::Visitors::Informix,
-    }
-
-    ENGINE_VISITORS = Hash.new do |hash, engine|
-      pool         = engine.connection_pool
-      adapter      = pool.spec.config[:adapter]
-      hash[engine] = (VISITORS[adapter] || Visitors::ToSql).new(engine)
-    end
-
-    def self.visitor_for engine
-      ENGINE_VISITORS[engine]
-    end
-    class << self; alias :for :visitor_for; end
   end
 end