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No database selected error after explicit declaration_base

I'm having this issue, where sqlalchemy does not recognize the database, even though it is declared with declarative_base. After trying to run a simple query of session.query(AppGeofencing).all() I get sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (1046, 'No database selected').
The table is declared as
Base = declarative_base()
AppBase = declarative_base(metadata=MetaData(schema='app'))
class AppGeofencing(AppBase):
__tablename__ = 'geofencing'
id = Column(INTEGER, primary_key=True, autoincrement=True)
name = Column(VARCHAR(45))
polygon = Column(Geometry('POLYGON'))
def __init__(self, name=None, polygon=None):
self.name = name
self.polygon = polygon
The case is only with this table, because I have also done similarly for other tables, and they work just fine.
After enabling the logging for sqlalchemy I can see that is does indeed create the correct query
INFO:sqlalchemy.engine.Engine:SELECT app.geofencing.id AS app_geofencing_id, app.geofencing.name AS app_geofencing_name, ST_AsEWKB(app.geofencing.polygon) AS app_geofencing_polygon
FROM app.geofencing
but somehow it cannot determine the database to use?
Does anyone have any idea, what could cause such issue?

Why I receive sqlalchemy.exc.IntegrityError

I faced with error, the sense of witch I can't understand:
I write to models:
class User(db.Model):
__tablename__ = 'users'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(255))
class UserFile(db.Model):
__tablename__ = 'user_files'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(255))
author_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False)
author = db.relationship(User, foreign_keys=[author_id])
I need to do a number of additional steps when I delete a UserFile instance.
When a UserFile instance is deleted directly, I can do whatever I need to do. There is a problem when the User instance is deleted. In this case, I need to remove all UserFile instances associated with the User. But I can't use cascade deletion, because I need to perform additional actions for each UserFile.
I tried using SQLAlchemy 'before_delete' event, but I got an error because it was already running after deletion, although it was called 'before'. I saw this by adding output of the message to the console and not seeing this message in the console until I got the error.
Then I tried using FLASK-sqlalchemy signals. I did:
from flask_sqlalchemy import before_models_committed
#before_models_committed.connect_via(app)
def delete_all_user_folders_after_delete(sender, changes):
for obj, operation in changes:
if isinstance(obj, User) and operation == 'delete':
print('files: ', UserFile.query.filter_by(author_id=obj.id, parent_id=None).all())
for item in UserFile.query.filter_by(author_id=obj.id,
parent_id=None).all():
print(item)
delete_file(item, True)
And got error on line:
print ('files: ', UserFile.query.filter_by(author_id=obj.id, parent_id=None).all())
What is the cause of this error and how do I properly pre-delete all Userfiles before deleting a User?
Error description:
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) update or delete on table "users" violates foreign key constraint "user_files_author_id_fkey" on table "user_files"
DETAIL: Key (id)=(2) is still referenced from table "user_files".

The query performed in delete_all_user_folders_after_delete() causes autoflush, which flushes the deletions prematurely, before your manual cleanup has been done. The default referential action in PostgreSQL is NO ACTION, which "means that if any referencing rows still exist when the constraint is checked, an error is raised". It would seem that you have not deferred the constraint in question, so it is checked immediately.
You could perhaps try the solution proposed in the error message:
#before_models_committed.connect_via(app)
def delete_all_user_folders_after_delete(sender, changes):
for obj, operation in changes:
if isinstance(obj, User) and operation == 'delete':
with db.session.no_autoflush:
fs = UserFile.query.filter_by(author_id=obj.id, parent_id=None).all()
print('files: ', fs)
for item in fs:
print(item)
# If this queries the DB, remember to disable autoflush again
delete_file(item, True)

sqlalchemy one-to-many ORM update error

I have two tables: Eca_users and Eca_user_emails, one user can have many emails. I recive json with users and their emails. And I wont to load them into MS SQL database. Users can update their emails, so in this json I can get the same users with new (or changed) emails.
My code
# some import here
Base = declarative_base()
class Eca_users(Base):
__tablename__ = 'eca_users'
sql_id = sqlalchemy.Column(sqlalchemy.Integer(), primary_key = True)
first_id = sqlalchemy.Column(sqlalchemy.String(15))
name = sqlalchemy.Column(sqlalchemy.String(200))
main_email = sqlalchemy.Column(sqlalchemy.String(200))
user_emails = relationship("Eca_user_emails", backref=backref('eca_users'))
class Eca_user_emails(Base):
__tablename__ = 'user_emails'
sql_id = sqlalchemy.Column(sqlalchemy.Integer(), primary_key = True)
email_address = Column(String(200), nullable=False)
status = Column(String(10), nullable=False)
active = Column(DateTime, nullable=True)
sql_user_id = Column(Integer, ForeignKey('eca_users.sql_id'))
def main()
engine = sqlalchemy.create_engine('mssql+pymssql://user:pass/ECAusers?charset=utf8')
Session = sessionmaker()
Session.configure(bind = engine)
session = Session()
#then I get my json, parse it and...
query = session.query(Eca_users).filter(Eca_users.first_id == str(user_id))
if query.count() == 0:
# not interesting now
else:
for exstUser in query:
exstUser.name = name #update user info
exstUser.user_emails = [:] # empty old emails
# creating new Email obj
newEmail = Eca_user_emails(email_address = email_record['email'],
status = email_record['status'],
active = active_date)
exstUser.user_emails.append(newEmail) # and I get error here because autoflush
session.commit()
if __name__ == '__main__':
main()
Error message:
sqlalchemy.exc.IntegrityError: ...
[SQL: 'UPDATE user_emails SET sql_user_id=%(sql_user_id)s WHERE user_emails.sql_id = %(user_emails_sql_id)s'] [parameters: {'sql_user_id': None, 'user_emails_sql_id': Decimal('1')}]
Can't find any idea why this sql_user_id is None :(
When I chek exstUser and newEmail objects in debugger - it looks like everething fine. I mean all the reference is OK. The session obj and it's dirty attribute looks also OK in the debugger (sql_user_id is set for Eca_user_emails obj).
And what is most strange for me - this code worked absolutely fine when it was without a main function, just all code after the classes declaration. But after I wrote main declaration and put all code here I started to get this error.
I am completely new to Python so maybe this is one of stupid mistakes...
Any ideas how to fix it and what is the reason? Thanks for reading this :)
By the way: Python 3.4, sqlalchemy 1.0, SQL Server 2012

sql_user_id is None because by default SQLAlchemy clears out the foreign key when you delete a child object across a relationship, that is, when you clear exstUser.user_emails SQLAlchemy sets sql_user_id to None for all those instances. If you want SQLAlchemy to issue DELETEs for Eca_user_emails instances when they are detached from Eca_users, you need to add delete-orphan cascade option to the user_emails relationship. If you want SQLAlchemy to issue DELETEs for Eca_user_emails instances when a Eca_users instance is deleted, you need to add the delete cascade option to the user_emails relationship.
user_emails = relationship("Eca_user_emails", backref=backref('eca_users'), cascade="save-update, merge, delete, delete-orphan")
You can find more information about cascades in the SQLAlchemy docs

Get last inserted value from MySQL using SQLAlchemy

I've just run across a fairly vexing problem, and after testing I have found that NONE of the available answers are sufficient.
I have seen various suggestions but none seem to be able to return the last inserted value for an auto_increment field in MySQL.
I have seen examples that mention the use of session.flush() to add the record and then retrieve the id. However that always seems to return 0.
I have also seen examples that mention the use of session.refresh() but that raises the following error: InvalidRequestError: Could not refresh instance ''
What I'm trying to do seems insanely simple but I can't seem to figure out the secret.
I'm using the declarative approach.
So, my code looks something like this:
class Foo(Base):
__tablename__ = 'tblfoo'
__table_args__ = {'mysql_engine':'InnoDB'}
ModelID = Column(INTEGER(unsigned=True), default=0, primary_key=True, autoincrement=True)
ModelName = Column(Unicode(255), nullable=True, index=True)
ModelMemo = Column(Unicode(255), nullable=True)
f = Foo(ModelName='Bar', ModelMemo='Foo')
session.add(f)
session.flush()
At this point, the object f has been pushed to the DB, and has been automatically assigned a unique primary key id. However, I can't seem to find a way to obtain the value to use in some additional operations. I would like to do the following:
my_new_id = f.ModelID
I know I could simply execute another query to lookup the ModelID based on other parameters but I would prefer not to if at all possible.
I would much appreciate any insight into a solution to this problem.
Thanks for the help in advance.

The problem is you are setting defaul for the auto increment. So when it run the insert into query the log of server is
2011-12-21 13:44:26,561 INFO sqlalchemy.engine.base.Engine.0x...1150 INSERT INTO tblfoo (`ModelID`, `ModelName`, `ModelMemo`) VALUES (%s, %s, %s)
2011-12-21 13:44:26,561 INFO sqlalchemy.engine.base.Engine.0x...1150 (0, 'Bar', 'Foo')
ID : 0
So the output is 0 which is the default value and which is passed because you are setting default value for autoincrement column.
If I run same code without default then it give the correct output.
Please try this code
from sqlalchemy import create_engine
engine = create_engine('mysql://test:test#localhost/test1', echo=True)
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
from sqlalchemy.orm import sessionmaker
Session = sessionmaker(bind=engine)
session = Session()
from sqlalchemy import Column, Integer, Unicode
class Foo(Base):
__tablename__ = 'tblfoo'
__table_args__ = {'mysql_engine':'InnoDB'}
ModelID = Column(Integer, primary_key=True, autoincrement=True)
ModelName = Column(Unicode(255), nullable=True, index=True)
ModelMemo = Column(Unicode(255), nullable=True)
Base.metadata.create_all(engine)
f = Foo(ModelName='Bar', ModelMemo='Foo')
session.add(f)
session.flush()
print "ID :", f.ModelID

Try using session.commit() instead of session.flush(). You can then use f.ModelID.

Not sure why the flagged answer worked for you. But in my case, that does not actually insert the row into the table. I need to call commit() in the end.
So the last few lines of code are:
f = Foo(ModelName='Bar', ModelMemo='Foo')
session.add(f)
session.flush()
print "ID:", f.ModelID
session.commit()

How to write alter column name migrations with sqlalchemy-migrate?

I'm trying to alter a column name. First attempt was with this script:
meta = MetaData()
users = Table('users', meta,
Column('id', Integer, primary_key=True),
Column('name', String(50), unique=True),
Column('email', String(120), unique=True)
)
def upgrade(migrate_engine):
meta.bind = migrate_engine
users.c.id.alter(name='id')
def downgrade(migrate_engine):
meta.bind = migrate_engine
users.c.id.alter(name='user_id')
Running migrate.py test on my dev database (sqlite) works and so does upgrading and downgrading. But when deploying it to my test environment on Heroku (where PostgreSQL 8.3 is used) I get a trace when I try to upgrade. Gist is this message:
sqlalchemy.exc.ProgrammingError: (ProgrammingError) column "id" does not exist
I then tried to use users.c.user_idin the upgrade method. That fails in both environments.:
AttributeError: user_id
The workaround I'm using now is this script:
meta_old = MetaData()
meta_new = MetaData()
users_old = Table('users', meta_old,
Column('user_id', Integer, primary_key=True),
Column('name', String(50), unique=True),
Column('email', String(120), unique=True)
)
users_new = Table('users', meta_new,
Column('id', Integer, primary_key=True),
Column('name', String(50), unique=True),
Column('email', String(120), unique=True)
)
def upgrade(migrate_engine):
meta_old.bind = migrate_engine
users_old.c.user_id.alter(name='id')
def downgrade(migrate_engine):
meta_new.bind = migrate_engine
users_new.c.id.alter(name='user_id')
It's already recommended practice to copy-paste the model to the sqlalchemy-migrate scripts. But this extra duplications gets a bit too much for me. Anyone knows how this should be done. Assuming it's a bug, I'd like suggestions on how to DRY up the workaround some.

This one also works:
from alembic import op
....
def upgrade(migrate_engine):
op.alter_column('users', 'user_id', new_column_name='id')
def downgrade(migrate_engine):
op.alter_column('users', 'id', new_column_name='user_id')

Turns out there's an even DRY:er solution to this than I had hoped for. Introspection! Like so:
def upgrade(migrate_engine):
meta = MetaData(bind=migrate_engine)
users = Table('users', meta, autoload=True)
users.c.user_id.alter(name='id')
def downgrade(migrate_engine):
meta = MetaData(bind=migrate_engine)
users = Table('users', meta, autoload=True)
users.c.id.alter(name='user_id')
Works like a charm!

I bet that it can't generate any SQL because your metadata references are getting mixed up. You seem to be using two different metadata objects in your Table classes, and that's really not good. You only need one. The metadata tracks stale-ness of objects, whether it needs to issue queries for object updates, foreign key constraints, etc. and it needs to know about all your tables and relationships.
Change to use a single MetaData object, and pass echo=True to your sqlalchemy.create_engine call and it will print the SQL query that it's using to standard output. Try executing that query yourself while logged in as the same role (user) to Postgres. You may find that it's a simple permissions issue.
Regarding copy-pasting: I think Django has a good convention of placing Table and declarative classes in their own module and importing them. However, because you have to pass a MetaData object to the Table factory, that complicates matters. You can use a singleton/global metadata object, or just convert to declarative.
For a while I chose to implement one-argument functions that returned Table objects given a metadata and cached the result--in effect implementing a singleton model class. Then I decided that was silly and switched to declarative.