MySQL: fix show_variable. Closes #8448.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@7071 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* MySQL: fix show_variable.  #8448 [matt, Jeremy Kemper]
+
 * Fixtures: correctly delete and insert fixtures in a single transaction.  #8553 [Michael Schuerig]
 
 * Fixtures: people(:technomancy, :josh) returns both fixtures.  #7880 [technomancy, Josh Peek]

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -409,7 +409,8 @@ module ActiveRecord
 
       # SHOW VARIABLES LIKE 'name'
       def show_variable(name)
-        select_value "SHOW VARIABLES LIKE '#{name}'"
+        variables = select_all("SHOW VARIABLES LIKE '#{name}'")
+        variables.first['Value'] unless variables.empty?
       end
 
       private

activerecord/test/adapter_test.rb

@@ -48,11 +48,19 @@ class AdapterTest < Test::Unit::TestCase
 
   if current_adapter?(:MysqlAdapter)
     def test_charset
-      assert @connection.charset
+      assert_not_nil @connection.charset
+      assert_not_equal 'character_set_database', @connection.charset
+      assert_equal @connection.show_variable('character_set_database'), @connection.charset
     end
 
     def test_collation
-      assert @connection.collation
+      assert_not_nil @connection.collation
+      assert_not_equal 'collation_database', @connection.collation
+      assert_equal @connection.show_variable('collation_database'), @connection.collation
+    end
+
+    def test_show_nonexistent_variable_returns_nil
+      assert_nil @connection.show_variable('foo_bar_baz')
     end
   end