1 files changed, 86 insertions, 0 deletions
diff --git a/activerecord/lib/arel/visitors/mysql.rb b/activerecord/lib/arel/visitors/mysql.rb
new file mode 100644
index 0000000000..4c734f6292
--- /dev/null
+++ b/activerecord/lib/arel/visitors/mysql.rb
@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+module Arel
+  module Visitors
+    class MySQL < Arel::Visitors::ToSql
+      private
+      def visit_Arel_Nodes_Union o, collector, suppress_parens = false
+        unless suppress_parens
+          collector << "( "
+        end
+
+        collector =   case o.left
+                      when Arel::Nodes::Union
+                        visit_Arel_Nodes_Union o.left, collector, true
+                      else
+                        visit o.left, collector
+                      end
+
+        collector << " UNION "
+
+        collector =    case o.right
+                       when Arel::Nodes::Union
+                         visit_Arel_Nodes_Union o.right, collector, true
+                       else
+                         visit o.right, collector
+                       end
+
+        if suppress_parens
+          collector
+        else
+          collector << " )"
+        end
+      end
+
+      def visit_Arel_Nodes_Bin o, collector
+        collector << "BINARY "
+        visit o.expr, collector
+      end
+
+      ###
+      # :'(
+      # http://dev.mysql.com/doc/refman/5.0/en/select.html#id3482214
+      def visit_Arel_Nodes_SelectStatement o, collector
+        if o.offset && !o.limit
+          o.limit = Arel::Nodes::Limit.new(18446744073709551615)
+        end
+        super
+      end
+
+      def visit_Arel_Nodes_SelectCore o, collector
+        o.froms ||= Arel.sql('DUAL')
+        super
+      end
+
+      def visit_Arel_Nodes_UpdateStatement o, collector
+        collector << "UPDATE "
+        collector = visit o.relation, collector
+
+        unless o.values.empty?
+          collector << " SET "
+          collector = inject_join o.values, collector, ', '
+        end
+
+        unless o.wheres.empty?
+          collector << " WHERE "
+          collector = inject_join o.wheres, collector, ' AND '
+        end
+
+        unless o.orders.empty?
+          collector << " ORDER BY "
+          collector = inject_join o.orders, collector, ', '
+        end
+
+        maybe_visit o.limit, collector
+      end
+
+      def visit_Arel_Nodes_Concat o, collector
+        collector << " CONCAT("
+        visit o.left, collector
+        collector << ", "
+        visit o.right, collector
+        collector << ") "
+        collector
+      end
+    end
+  end
+end