Efficient Pandas to MySQL “UPDATE… WHERE”

I have a pandas DataFrame and a (MySQL) database with the same columns. The database is not managed by me.

I want to update the values in the database in an "UPDATE... WHERE" style, updating only some columns wherever some other columns match.

Here's my code:

import sqlalchemy as sqla

def save_to_db(final_df, passwd):

    engine_str = 'mysql+mysqldb://username:{}@localhost/mydb'.format(passwd)

    engine = sqla.create_engine(engine_str)

    sm = sessionmaker(bind=engine)
    session = sm()

    metadata = sqla.MetaData(bind=engine)

    datatable = sqla.Table('AdcsLogForProduct', metadata, autoload=True)

    for ind, row in final_df.iterrows():
        u = sqla.sql.update(datatable) \
            .values({"q_ECI_B_x": row.q_ECI_B_x,
                     "q_ECI_B_y": row.q_ECI_B_y,
                     "q_ECI_B_z": row.q_ECI_B_z,
                     "q_ECI_B_s": row.q_ECI_B_s}) \
            .where(sqla.and_(datatable.c.year == row.year,
                             datatable.c.month == row.month,
                             datatable.c.day == row.day,
                             datatable.c.hours == row.hours,
                             datatable.c.minutes == row.minutes,
                             datatable.c.seconds == row.seconds,
                             datatable.c.milliseconds == row.milliseconds,
                             datatable.c.microseconds == row.microseconds))

        session.execute(u)

    session.flush()
    session.commit()

I'm doing this with plain sqlalchemy because apparently pandas' built-in SQL functions can't handle "UPDATE... WHERE" scenarios. However, this is really slow.

Isn't there a more efficient way to do this?