I've run into autoflush issue while using AssociationProxy with
sqlalchemy-1.1.6. Appending to association list fails, because object is
flushed before it is appended (and appending sets primary key value). I can
avoid it with session.no_autoflush context manager, but I wonder if it's
not worth slightly changing proxy behaviour to make it work with autoflush
enabled.
Minimal example of this issue below:
engine = engine_from_config(CONFIG)
DBSession = scoped_session(sessionmaker())
DBSession.configure(bind=engine)
Base = declarative_base()
class UserAlias(Base):
__tablename__ = 'user_aliases'
user_id = Column(Integer, ForeignKey('user.id'), primary_key=True)
alias_id = Column(Integer, ForeignKey('aliases.id'), primary_key=True)
valid = Column(Boolean)
alias = relationship('Alias', backref=backref('user_assocs', uselist=
False))
user = relationship('User', backref=backref('alias_assocs'))
def __init__(self, alias, valid=True):
self.alias = alias
self.valid = valid
class Alias(Base):
__tablename__ = 'aliases'
id = Column(Integer, primary_key=True)
name = Column('name', String(64))
user = association_proxy('user_assocs', 'user')
def __init__(self, name):
self.name = name
class User(Base):
__tablename__ = 'user'
id = Column(Integer, primary_key=True)
name = Column(String(64))
aliases = association_proxy('alias_assocs', 'alias')
def __init__(self, name):
self.name = name
def test_assoc():
user = User(name='John')
DBSession.add(user)
DBSession.commit()
johny = Alias(name='Johny')
user.aliases.append(johny)
DBSession.commit()
jan = Alias(name='Jan')
DBSession.add(jan) # in my real use case proxied object is already
attached to session before appending, here I simulate it with DBSession.add
user.aliases.append(jan) # autoflush fails here
DBSession.commit()
return user
and stacktrace:
/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/sql
/crud.py:692: SAWarning: Column 'user_aliases.user_id' is marked as a
member of the primary key for table 'user_aliases', but has no Python-side
or server-side default generator indicated, nor does it indicate
'autoincrement=True' or 'nullable=True', and no explicit value is passed.
Primary key columns typically may not store NULL. Note that as of SQLAlchemy
1.1, 'autoincrement=True' must be indicated explicitly for composite (e.g.
multicolumn) primary keys if AUTO_INCREMENT/SERIAL/IDENTITY behavior is
expected for one of the columns in the primary key. CREATE TABLE statements
are impacted by this change as well on most backends.
util.warn(msg)
Traceback (most recent call last):
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/engine/base.py"
, line 1182, in _execute_context
context)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/engine/default.py"
, line 470, in do_execute
cursor.execute(statement, parameters)
psycopg2.IntegrityError: null value in column "user_id" violates not-null
constraint
DETAIL: Failing row contains (null, 50, t).
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/home/bartek/dev/sqlalchemy-test/sqlalchemy_test/models.py", line
111, in <module>
test_assoc()
File "/home/bartek/dev/sqlalchemy-test/sqlalchemy_test/models.py", line
105, in test_assoc
user.aliases.append(jan)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/ext/associationproxy.py"
, line 610, in append
self.col.append(item)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/ext/associationproxy.py"
, line 509, in <lambda>
col = property(lambda self: self.lazy_collection())
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/ext/associationproxy.py"
, line 467, in __call__
return getattr(obj, self.target)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/attributes.py"
, line 237, in __get__
return self.impl.get(instance_state(instance), dict_)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/attributes.py"
, line 584, in get
value = self.callable_(state, passive)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/strategies.py"
, line 557, in _load_for_state
return self._emit_lazyload(session, state, ident_key, passive)
File "<string>", line 1, in <lambda>
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/strategies.py"
, line 635, in _emit_lazyload
result = q.all()
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/query.py"
, line 2679, in all
return list(self)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/query.py"
, line 2830, in __iter__
self.session._autoflush()
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/session.py"
, line 1375, in _autoflush
util.raise_from_cause(e)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/util/compat.py"
, line 203, in raise_from_cause
reraise(type(exception), exception, tb=exc_tb, cause=cause)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/util/compat.py"
, line 187, in reraise
raise value
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/session.py"
, line 1365, in _autoflush
self.flush()
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/session.py"
, line 2139, in flush
self._flush(objects)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/session.py"
, line 2259, in _flush
transaction.rollback(_capture_exception=True)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/util/langhelpers.py"
, line 60, in __exit__
compat.reraise(exc_type, exc_value, exc_tb)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/util/compat.py"
, line 187, in reraise
raise value
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/session.py"
, line 2223, in _flush
flush_context.execute()
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/unitofwork.py"
, line 389, in execute
rec.execute(self)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/unitofwork.py"
, line 548, in execute
uow
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/persistence.py"
, line 181, in save_obj
mapper, table, insert)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/orm/persistence.py"
, line 835, in _emit_insert_statements
execute(statement, params)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/engine/base.py"
, line 945, in execute
return meth(self, multiparams, params)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/sql/elements.py"
, line 263, in _execute_on_connection
return connection._execute_clauseelement(self, multiparams, params)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/engine/base.py"
, line 1053, in _execute_clauseelement
compiled_sql, distilled_params
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/engine/base.py"
, line 1189, in _execute_context
context)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/engine/base.py"
, line 1393, in _handle_dbapi_exception
exc_info
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/util/compat.py"
, line 203, in raise_from_cause
reraise(type(exception), exception, tb=exc_tb, cause=cause)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/util/compat.py"
, line 186, in reraise
raise value.with_traceback(tb)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/engine/base.py"
, line 1182, in _execute_context
context)
File
"/home/bartek/envs/sqlalchemy-test/lib/python3.5/site-packages/sqlalchemy/engine/default.py"
, line 470, in do_execute
cursor.execute(statement, parameters)
sqlalchemy.exc.IntegrityError: (raised as a result of Query-invoked
autoflush; consider using a session.no_autoflush block if this flush is
occurring prematurely) (psycopg2.IntegrityError) null value in column
"user_id" violates not-null constraint
DETAIL: Failing row contains (null, 50, t).
[SQL: 'INSERT INTO user_aliases (alias_id, valid) VALUES (%(alias_id)s,
%(valid)s)'] [parameters: {'alias_id': 50, 'valid': True}]
Autoflush occurs in _AssociationList append method:
def append(self, value):
item = self._create(value)
self.col.append(item)
If _create was called before self.col is evaluted created object would not
be autoflushed prematurely. Maybe it is worth changing it if it does not
break anything else.
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
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