Comment 1 for bug 1004991

At this point, I've traced this down to 'mysql_stmt_result_metadata(stmt)' returning NULL when a stored procedure is called.

According to some bug reports,
 http://bugs.mysql.com/bug.php?id=42490
http://bugs.mysql.com/bug.php?id=19008
http://bugs.mysql.com/bug.php?id=11918

The relevant section from the manual:
"The multiple statement and result capabilities can be used only with mysql_query() or mysql_real_query(). They cannot be used with the prepared statement interface. Prepared statement handles are defined to work only with strings that contain a single statement. See Section 22.8.4, “C API Prepared Statements”."
http://dev.mysql.com/doc/refman/5.5/en/c-api-multiple-queries.html

So the answer is "you cannot call a stored procedure from mysql_stmt_query() if you want any results" :(

In order to do what you want to do (use CALL) you have to do the escaping manually yourself, and use curs.execute("CALL foo(1,2,3)", plain_query=True)