1 files changed, 20 insertions, 0 deletions
diff --git a/lib/arel/visitors.rb b/lib/arel/visitors.rb
index 22077d5943..879635575b 100644
--- a/lib/arel/visitors.rb
+++ b/lib/arel/visitors.rb
@@ -4,3 +4,23 @@ require 'arel/visitors/mysql'
 require 'arel/visitors/join_sql'
 require 'arel/visitors/order_clauses'
 require 'arel/visitors/dot'
+
+module Arel
+  module Visitors
+    VISITORS = {
+      'postgresql' => Arel::Visitors::PostgreSQL,
+      'mysql'      => Arel::Visitors::MySQL,
+      'mysql2'     => Arel::Visitors::MySQL,
+    }
+
+    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
+  end
+end