Dump the 'using' options for a SQL index into the schema.

activerecord/lib/active_record/schema_dumper.rb

@@ -185,6 +185,8 @@ def indexes(table, stream)
 
             statement_parts << ('where: ' + index.where.inspect) if index.where
 
+            statement_parts << ('using: ' + index.using.inspect) if index.using
+
             '  ' + statement_parts.join(', ')
           end
 

activerecord/test/cases/schema_dumper_test.rb

@@ -177,13 +177,19 @@ def test_schema_dump_illegal_ignored_table_value
 
   def test_schema_dumps_index_columns_in_right_order
     index_definition = standard_dump.split(/\n/).grep(/add_index.*companies/).first.strip
-    assert_equal 'add_index "companies", ["firm_id", "type", "rating"], name: "company_index"', index_definition
+    if current_adapter?(:MysqlAdapter) or current_adapter?(:Mysql2Adapter) or current_adapter?(:PostgreSQLAdapter)
+       assert_equal 'add_index "companies", ["firm_id", "type", "rating"], name: "company_index", using: :btree', index_definition
+     else
+       assert_equal 'add_index "companies", ["firm_id", "type", "rating"], name: "company_index"', index_definition
+    end
   end
 
   def test_schema_dumps_partial_indices
     index_definition = standard_dump.split(/\n/).grep(/add_index.*company_partial_index/).first.strip
     if current_adapter?(:PostgreSQLAdapter)
-      assert_equal 'add_index "companies", ["firm_id", "type"], name: "company_partial_index", where: "(rating > 10)"', index_definition
+      assert_equal 'add_index "companies", ["firm_id", "type"], name: "company_partial_index", where: "(rating > 10)", using: :btree', index_definition
+    elsif current_adapter?(:MysqlAdapter) or current_adapter?(:Mysql2Adapter)
+      assert_equal 'add_index "companies", ["firm_id", "type"], name: "company_partial_index", using: :btree', index_definition
     else
       assert_equal 'add_index "companies", ["firm_id", "type"], name: "company_partial_index"', index_definition
     end

activerecord/test/schema/schema.rb

@@ -183,6 +183,7 @@ def create_table(*args, &block)
 
   add_index :companies, [:firm_id, :type, :rating], :name => "company_index"
   add_index :companies, [:firm_id, :type], :name => "company_partial_index", :where => "rating > 10"
+  add_index :companies, :name, :name => 'company_name_index', :using => :btree
 
   create_table :vegetables, :force => true do |t|
     t.string :name