Mysql transactions via ruby

Hi,
I’m trying to use transactions via “ruby mysql module” but there is no
effect, just like the autocommit mode on.

for example:

mSql.query("set autocommit=0")
mSql.query("start transaction")
mSql.query("insert into TEST values ('ABCD')")
mSql.query("rollback")

the record remains in the table.

I’m using Mysql 5.0, Ruby 1.8, table engine InnoDB. The same sql
operations
works fine on mysql console.

any suggestion?
thanks