I'm new to both python and SQLAlchemy, but am improving. I'm building
a new application that will use a sqlite database. A unit test is
failing with this exception:
"sqlalchemy.exceptions.ConcurrentModificationError: Updated rowcount 0
does not match number of objects updated 1"
Below is a small version of what I'm trying to do. Is this a
SQLAlchemy bug or do I need to be doing something differently? The
error happens on the final flush() call.
####################################
import sqlalchemy as sqla
db_con = sqla.create_engine('sqlite:///:memory:')
metadata = sqla.BoundMetaData(db_con)
signal_types = sqla.Table('signal_types', metadata,
sqla.Column('signal_type_id',
sqla.Integer,
primary_key = True),
sqla.Column('signal_type_name',
sqla.String(25),
nullable = False,
unique = True),
sqla.UniqueConstraint('signal_type_name',
name = 'signal_types_idx1')
)
signal_enumerations = sqla.Table('signal_enumerations', metadata,
sqla.Column('signal_type_id',
sqla.Integer,
sqla.ForeignKey('signal_types.signal_type_id'),
nullable = False),
sqla.Column('signal_enumeration_name',
sqla.String(50),
nullable = False),
sqla.Column('signal_enumeration_value',
sqla.Integer,
nullable = False),
sqla.PrimaryKeyConstraint('signal_type_id', 'signal_enumeration_name')
)
metadata.create_all()
session = sqla.create_session(db_con)
class Signal_type(object):
"Model class for the Signal_types table"
def __init__(self, name):
self.signal_type_name = name
class Signal_enumeration(object):
"Model class for the Signal_enumeration table"
def __init__(self, name, value):
self.signal_enumeration_name = name
self.signal_enumeration_value = value
def __repr__(self):
return "%s: %d" % (self.signal_enumeration_name,
self.signal_enumeration_value)
# Table signal_types
# Primary Key: signal_type_id
signal_types_mapper = sqla.mapper(Signal_type, signal_types)
# Table signal_enumerations
# Primary Key: signal_enumeration_name
# Foreign Key: signal_types(signal_type_id)
sqla.mapper(Signal_enumeration, signal_enumerations)
signal_types_mapper.add_property('enumerations',
sqla.relation(Signal_enumeration,
order_by = signal_enumerations.c.signal_enumeration_value,
cascade = "all, delete-orphan"))
###########################################################################
# Add database data
new_type = Signal_type('enum_type')
new_type.enumerations.append(Signal_enumeration('one', 1))
new_type.enumerations.append(Signal_enumeration('two', 2))
new_type.enumerations.append(Signal_enumeration('three', 3))
new_type.enumerations.append(Signal_enumeration('four', 4))
session.save(new_type)
session.flush()
new_type.enumerations[2].signal_enumeration_name = 'thirty'
#session.flush()
new_type.enumerations[2].signal_enumeration_value = 30
session.flush()
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