Fixed #15527 -- Added a explanatory note about the SQL debug log. Thanks to boxm for the report, and jpaulett for the draft patch

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15897 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/topics/logging.txt

@@ -458,6 +458,10 @@ Messages to this logger have the following extra context:
     * ``sql``: The SQL statement that was executed.
     * ``params``: The parameters that were used in the SQL call.
 
+For performance reasons, SQL logging is only occurs when
+``settings.DEBUG`` is set to ``True``, regardless of the logging
+level or handlers that are installed.
+
 .. note::
     Due to a limitation in the logging library, this extra
     context is not available if you are using Python 2.4.