Recursive query in mysql
Here is my working theory: Because you have the table data in InnoDB it may subjected to MVCC and Transaction Isolation in the midst of the InnoDB Infrastructure.

Please notice in my original post that I used MyISAM tables, which are not subject to ACID compliance.

Make a copy of the table, convert it to MyISAM, and run GetAncestry against it. You should find better performance.

Give it a Try !!!