SQLAlchemy insert data dumped on the database A into the database B - mysql

Question

What is the most effective way to insert data dumped on the database A into the database B? Normally I would use mysqldump for the task like this, but because of the complex query I had to take a different approach. At present I have the following inefficient solution:
from sqlalchemy import create_engine, Column, INTEGER, CHAR, VARCHAR
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
SessFactory = sessionmaker()
print('## Configure database connections')
db_one = create_engine('mysql://root:pwd1#127.0.0.1/db_one', echo=True).connect()
sess_one = SessFactory(bind=db_one)
db_two = create_engine('mysql://root:pwd2#127.0.0.2/db_two', echo=True).connect()
sess_two = SessFactory(bind=db_two)
## Declare query to dump data
dump_query = (
'SELECT A.id, A.name, B.address '
'FROM table_a A JOIN table_b B '
'ON A.id = B.id_c WHERE '
'A.deleted = 0'
)
print('## Fetch data on db_one')
data = db_one.execute(dump_query).fetchall()
## Declare table on db_two
class cstm_table(Base):
__tablename__ = 'cstm_table'
pk = Column(INTEGER, primary_key=True)
id = Column(CHAR(36), nullable=False)
name = Column(VARCHAR(150), default=None)
address = Column(VARCHAR(150), default=None)
print('## Recreate "cstm_table" on db_two')
cstm_table.__table__.drop(bind=db_two, checkfirst=True)
cstm_table.__table__.create(bind=db_two)
print('## Insert dumped data into the "cstm_table" on db_two')
for row in data:
insert = cstm_table.__table__.insert().values(row)
db_two.execute(insert)
This execute sequentially over a 100K inserts (horrible).
I also tried:
with db_two.connect() as conn:
with conn.begin() as trans:
row_as_dict = [dict(row.items()) for row in data]
try:
conn.execute(cstm_table.__table__.insert(), row_as_dict)
except:
trans.rollback()
raise
else:
trans.commit()
But then after inserting ~20 rows I get error:
OperationalError: (_mysql_exceptions.OperationalError) (2006, 'MySQL server has gone away')
The following also does the job, but I'm not so sure it's the most efficient:
sess_two.add_all([cstm_table(**dict(row.items())) for row in data])
sess_two.flush()
sess_two.commit()