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• sqlalchemy date type in 0.6 migration using mssql

  - by nosklo

  I'm connection to mssql server through pyodbc, via FreeTDS odbc driver, on linux ubuntu 10.04. Sqlalchemy 0.5 uses DATETIME for sqlalchemy.Date() fields. Now Sqlalchemy 0.6 uses DATE, but sql server 2000 doesn't have a DATE type. How can I make DATETIME be the default for sqlalchemy.Date() on sqlalchemy 0.6 mssql+pyodbc dialect? I'd like to keep it as clean as possible. Here's code to reproduce the issue: import sqlalchemy from sqlalchemy import Table, Column, MetaData, Date, Integer, create_engine engine = create_engine( 'mssql+pyodbc://sa:sa@myserver/mydb?driver=FreeTDS') m = MetaData(bind=engine) tb = sqlalchemy.Table('test_date', m, Column('id', Integer, primary_key=True), Column('dt', Date()) ) tb.create() And here is the traceback I'm getting: Traceback (most recent call last): File "/tmp/teste.py", line 15, in <module> tb.create() File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/schema.py", line 428, in create bind.create(self, checkfirst=checkfirst) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1647, in create connection=connection, **kwargs) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1682, in _run_visitor **kwargs).traverse_single(element) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/sql/visitors.py", line 77, in traverse_single return meth(obj, **kw) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/ddl.py", line 58, in visit_table self.connection.execute(schema.CreateTable(table)) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1157, in execute params) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1210, in _execute_ddl return self.__execute_context(context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1268, in __execute_context context.parameters[0], context=context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1367, in _cursor_execute context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1360, in _cursor_execute context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/default.py", line 277, in do_execute cursor.execute(statement, parameters) sqlalchemy.exc.ProgrammingError: (ProgrammingError) ('42000', '[42000] [FreeTDS][SQL Server]Column or parameter #2: Cannot find data type DATE. (2715) (SQLExecDirectW)') '\nCREATE TABLE test_date (\n\tid INTEGER NOT NULL IDENTITY(1,1), \n\tdt DATE NULL, \n\tPRIMARY KEY (id)\n)\n\n' ()

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• OperationalError "unable to open database file" processing query results with SQLAlchemy and SQLite3

  - by Peter

  I'm running into this little problem that I hope is just a dumb user error. It looks like some sort of a size limit with a query to a SQLite database. I managed to reproduce the issue with an in-memory DB and a simple script shown below. I can make it work by either reducing the number of records in the DB; or by reducing the size of each record; or by dropping the order_by() call. I am using Python 2.5.5 and SQLAlchemy 0.6.0 in a Cygwin environment. Thanks! #!/usr/bin/python from sqlalchemy.orm import sessionmaker import sqlalchemy import sqlalchemy.orm class Person(object): def __init__(self, name): self.name = name engine = sqlalchemy.create_engine('sqlite:///:memory:') Session = sessionmaker(bind=engine) metadata = sqlalchemy.schema.MetaData(bind=engine) person_table = sqlalchemy.Table('person', metadata, sqlalchemy.Column('id', sqlalchemy.types.Integer, primary_key=True), sqlalchemy.Column('name', sqlalchemy.types.String)) metadata.create_all(engine) sqlalchemy.orm.mapper(Person, person_table) session = Session() session.add_all([Person("012345678901234567890123456789012") for i in range(5000)]) session.commit() persons = session.query(Person).order_by(Person.name).all() print "count =", len(persons) session.close() The all() call to the query result fails with the OperationalError exception: Traceback (most recent call last): File "./stress.py", line 27, in <module> persons = session.query(Person).order_by(Person.name).all() File "/usr/lib/python2.5/site-packages/sqlalchemy/orm/query.py", line 1343, in all return list(self) File "/usr/lib/python2.5/site-packages/sqlalchemy/orm/query.py", line 1451, in __iter__ return self._execute_and_instances(context) File "/usr/lib/python2.5/site-packages/sqlalchemy/orm/query.py", line 1456, in _execute_and_instances mapper=self._mapper_zero_or_none()) File "/usr/lib/python2.5/site-packages/sqlalchemy/orm/session.py", line 737, in execute clause, params or {}) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/base.py", line 1109, in execute return Connection.executors[c](self, object, multiparams, params) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/base.py", line 1186, in _execute_clauseelement return self.__execute_context(context) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/base.py", line 1215, in __execute_context context.parameters[0], context=context) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/base.py", line 1284, in _cursor_execute self._handle_dbapi_exception(e, statement, parameters, cursor, context) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/base.py", line 1282, in _cursor_execute self.dialect.do_execute(cursor, statement, parameters, context=context) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/default.py", line 277, in do_execute cursor.execute(statement, parameters) sqlalchemy.exc.OperationalError: (OperationalError) unable to open database file u'SELECT person.id AS person_id, person.name AS person_name \nFROM person ORDER BY person.name' ()

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• Starter question of declarative style SQLAlchemy relation()

  - by jfding

  I am quite new to SQLAlchemy, or even database programming, maybe my question is too simple. Now I have two class/table: class User(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String(40)) ... class Computer(Base): __tablename__ = 'comps' id = Column(Integer, primary_key=True) buyer_id = Column(None, ForeignKey('users.id')) user_id = Column(None, ForeignKey('users.id')) buyer = relation(User, backref=backref('buys', order_by=id)) user = relation(User, backref=backref('usings', order_by=id)) Of course, it cannot run. This is the backtrace: File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/state.py", line 71, in initialize_instance fn(self, instance, args, kwargs) File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/mapper.py", line 1829, in _event_on_init instrumenting_mapper.compile() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/mapper.py", line 687, in compile mapper._post_configure_properties() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/mapper.py", line 716, in _post_configure_properties prop.init() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/interfaces.py", line 408, in init self.do_init() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/properties.py", line 716, in do_init self._determine_joins() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/properties.py", line 806, in _determine_joins "many-to-many relation, 'secondaryjoin' is needed as well." % (self)) sqlalchemy.exc.ArgumentError: Could not determine join condition between parent/child tables on relation Package.maintainer. Specify a 'primaryjoin' expression. If this is a many-to-many relation, 'secondaryjoin' is needed as well. There's two foreign keys in class Computer, so the relation() callings cannot determine which one should be used. I think I must use extra arguments to specify it, right? And howto? Thanks

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• Default class for SQLAlchemy single table inheritance

  - by eclaird

  I've set up a single table inheritance, but I need a "default" class to use when an unknown polymorphic identity is encountered. The database is not in my control and so the data can be pretty much anything. A working example setup: import sqlalchemy as sa from sqlalchemy import orm engine = sa.create_engine('sqlite://') metadata = sa.MetaData(bind=engine) table = sa.Table('example_types', metadata, sa.Column('id', sa.Integer, primary_key=True), sa.Column('type', sa.Integer), ) metadata.create_all() class BaseType(object): pass class TypeA(BaseType): pass class TypeB(BaseType): pass base_mapper = orm.mapper(BaseType, table, polymorphic_on=table.c.type, polymorphic_identity=None, ) orm.mapper(TypeA, inherits=base_mapper, polymorphic_identity='A', ) orm.mapper(TypeB, inherits=base_mapper, polymorphic_identity='B', ) Session = orm.sessionmaker(autocommit=False, autoflush=False) session = Session() Now, if I insert a new unmapped identity... engine.execute('INSERT INTO EXAMPLE_TYPES (TYPE) VALUES (\'C\')') session.query(BaseType).first() ...things break. Traceback (most recent call last): File "<stdin>", line 1, in <module> File ".../SQLAlchemy-0.6.5-py2.6.egg/sqlalchemy/orm/query.py", line 1619, in first ret = list(self[0:1]) File ".../SQLAlchemy-0.6.5-py2.6.egg/sqlalchemy/orm/query.py", line 1528, in __getitem__ return list(res) File ".../SQLAlchemy-0.6.5-py2.6.egg/sqlalchemy/orm/query.py", line 1797, in instances rows = [process[0](row, None) for row in fetch] File ".../SQLAlchemy-0.6.5-py2.6.egg/sqlalchemy/orm/mapper.py", line 2179, in _instance _instance = polymorphic_instances[discriminator] File ".../SQLAlchemy-0.6.5-py2.6.egg/sqlalchemy/util.py", line 83, in __missing__ self[key] = val = self.creator(key) File ".../SQLAlchemy-0.6.5-py2.6.egg/sqlalchemy/orm/mapper.py", line 2341, in configure_subclass_mapper discriminator) AssertionError: No such polymorphic_identity u'C' is defined What I expected: >>> result = session.query(BaseType).first() >>> result <BaseType object at 0x1c8db70> >>> result.type u'C' I think this used to work with some older version of SQLAlchemy, but I haven't been keeping up with the development lately. Any pointers on how to accomplish this?

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• Convert sqlalchemy row object to python dict

  - by Anurag Uniyal

  or a simple way to iterate over columnName, value pairs? My version of sqlalchemy is 0.5.6 Here is the sample code where I tried using dict(row), but it throws exception , TypeError: 'User' object is not iterable import sqlalchemy from sqlalchemy import * from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker print "sqlalchemy version:",sqlalchemy.__version__ engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() users_table = Table('users', metadata, Column('id', Integer, primary_key=True), Column('name', String), ) metadata.create_all(engine) class User(declarative_base()): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String) def __init__(self, name): self.name = name Session = sessionmaker(bind=engine) session = Session() user1 = User("anurag") session.add(user1) session.commit() # uncommenting next line throws exception 'TypeError: 'User' object is not iterable' #print dict(user1) # this one also throws 'TypeError: 'User' object is not iterable' for u in session.query(User).all(): print dict(u) Running this code on my system outputs: sqlalchemy version: 0.5.6 Traceback (most recent call last): File "untitled-1.py", line 37, in <module> print dict(u) TypeError: 'User' object is not iterable

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• SQLAlchemy DetachedInstanceError with regular attribute (not a relation)

  - by haridsv

  I just started using SQLAlchemy and get a DetachedInstanceError and can't find much information on this anywhere. I am using the instance outside a session, so it is natural that SQLAlchemy is unable to load any relations if they are not already loaded, however, the attribute I am accessing is not a relation, in fact this object has no relations at all. I found solutions such as eager loading, but I can't apply to this because this is not a relation. I even tried "touching" this attribute before closing the session, but it still doesn't prevent the exception. What could be causing this exception for a non-relational property even after it has been successfully accessed once before? Any help in debugging this issue is appreciated. I will meanwhile try to get a reproducible stand-alone scenario and update here. Update: This is the actual exception message with a few stacks: File "/home/hari/bin/lib/python2.6/site-packages/SQLAlchemy-0.6.1-py2.6.egg/sqlalchemy/orm/attributes.py", line 159, in __get__ return self.impl.get(instance_state(instance), instance_dict(instance)) File "/home/hari/bin/lib/python2.6/site-packages/SQLAlchemy-0.6.1-py2.6.egg/sqlalchemy/orm/attributes.py", line 377, in get value = callable_(passive=passive) File "/home/hari/bin/lib/python2.6/site-packages/SQLAlchemy-0.6.1-py2.6.egg/sqlalchemy/orm/state.py", line 280, in __call__ self.manager.deferred_scalar_loader(self, toload) File "/home/hari/bin/lib/python2.6/site-packages/SQLAlchemy-0.6.1-py2.6.egg/sqlalchemy/orm/mapper.py", line 2323, in _load_scalar_attributes (state_str(state))) DetachedInstanceError: Instance <ReportingJob at 0xa41cd8c> is not bound to a Session; attribute refresh operation cannot proceed The partial model looks like this: metadata = MetaData() ModelBase = declarative_base(metadata=metadata) class ReportingJob(ModelBase): __tablename__ = 'reporting_job' job_id = Column(BigInteger, Sequence('job_id_sequence'), primary_key=True) client_id = Column(BigInteger, nullable=True) And the field client_id is what is causing this exception with a usage like the below: Query: jobs = session \ .query(ReportingJob) \ .filter(ReportingJob.job_id == job_id) \ .all() if jobs: # FIXME(Hari): Workaround for the attribute getting lazy-loaded. jobs[0].client_id return jobs[0] This is what triggers the exception later out of the session scope: msg = msg + ", client_id: %s" % job.client_id

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• sqlalchemy relation through another (declarative)

  - by clayg

  Is anyone familiar with ActiveRecord's "has_many :through" relations for models? I'm not really a Rails guy, but that's basically what I'm trying to do. As a contrived example consider Projects, Programmers, and Assignments: from sqlalchemy import create_engine from sqlalchemy.orm import sessionmaker from sqlalchemy import Column, ForeignKey from sqlalchemy.types import Integer, String, Text from sqlalchemy.orm import relation from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Assignment(Base): __tablename__ = 'assignment' id = Column(Integer, primary_key=True) description = Column(Text) programmer_id = Column(Integer, ForeignKey('programmer.id')) project_id = Column(Integer, ForeignKey('project.id')) def __init__(self, description=description): self.description = description def __repr__(self): return '<Assignment("%s")>' % self.description class Programmer(Base): __tablename__ = 'programmer' id = Column(Integer, primary_key=True) name = Column(String(64)) assignments = relation("Assignment", backref='programmer') def __init__(self, name=name): self.name = name def __repr__(self): return '<Programmer("%s")>' % self.name class Project(Base): __tablename__ = 'project' id = Column(Integer, primary_key=True) name = Column(String(64)) description = Column(Text) assignments = relation("Assignment", backref='project') def __init__(self, name=name, description=description): self.name = name self.description = description def __repr__(self): return '<Project("%s", "%s...")>' % (self.name, self.description[:10]) engine = create_engine('sqlite://') Base.metadata.create_all(engine) Session = sessionmaker(bind=engine) session = Session() Projects have many Assignments. Programmers have many Assignments. (understatement?) But in my office at least, Programmers also have many Projects - I'd like this relationship to be inferred through the Assignments assigned to the Programmer. I'd like the Programmer model to have a attribute "projects" which will return a list of Projects associated to the Programmer through the Assignment model. me = session.query(Programmer).filter_by(name='clay').one() projects = session.query(Project).\ join(Project.assignments).\ join(Assignment.programmer).\ filter(Programmer.id==me.id).all() How can I describe this relationship clearly and simply using the sqlalchemy declarative syntax? Thanks!

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• How do I delete a foreign key in SQLAlchemy?

  - by Travis

  I'm using SQLAlchemy Migrate to keep track of database changes and I'm running into an issue with removing a foreign key. I have two tables, t_new is a new table, and t_exists is an existing table. I need to add t_new, then add a foreign key to t_exists. Then I need to be able to reverse the operation (which is where I'm having trouble). t_new = sa.Table("new", meta.metadata, sa.Column("new_id", sa.types.Integer, primary_key=True) ) t_exists = sa.Table("exists", meta.metadata, sa.Column("exists_id", sa.types.Integer, primary_key=True), sa.Column( "new_id", sa.types.Integer, sa.ForeignKey("new.new_id", onupdate="CASCADE", ondelete="CASCADE"), nullable=False ) ) This works fine: t_new.create() t_exists.c.new_id.create() But this does not: t_exists.c.new_id.drop() t_new.drop() Trying to drop the foreign key column gives an error: 1025, "Error on rename of '.\my_db_name\#sql-1b0_2e6' to '.\my_db_name\exists' (errno: 150)" If I do this with raw SQL, i can remove the foreign key manually then remove the column, but I haven't been able to figure out how to remove the foreign key with SQLAlchemy? How can I remove the foreign key, and then the column?

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• 'NoneType' object has no attribute 'get' error using SQLAlchemy

  - by Az

  I've been trying to map an object to a database using SQLAlchemy but have run into a snag. Version info if handy: [OS: Mac OSX 10.5.8 | Python: 2.6.4 | SQLAlchemy: 0.5.8] The class I'm going to map: class Student(object): def __init__(self, name, id): self.id = id self.name = name self.preferences = collections.defaultdict(set) self.allocated_project = None self.allocated_rank = 0 def __repr__(self): return str(self) def __str__(self): return "%s %s" %(self.id, self.name) Background: Now, I've got a function that reads in the necessary information from a text database into these objects. The function more or less works and I can easily access the information from the objects. Before the SQLAlchemy code runs, the function will read in the necessary info and store it into the Class. There is a dictionary called students which stores this as such: students = {} students[id] = Student(<all the info from the various "reader" functions>) Afterwards, there is an "allocation" algorithm that will allocate projects to student. It does that well enough. The allocated_project remains as None if a student is unsuccessful in getting a project. SQLAlchemy bit: So after all this happens, I'd like to map my object to a database table. Using the documentation, I've used the following code to only map certain bits. I also begin to create a Session. from sqlalchemy import * from sqlalchemy.orm import * engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() students_table = Table('studs', metadata, Column('id', Integer, primary_key=True), Column('name', String) ) metadata.create_all(engine) mapper(Student, students_table) Session = sessionmaker(bind=engine) sesh = Session() Now after that, I was curious to see if I could print out all the students from my students dictionary. for student in students.itervalues(): print student What do I get but an error: Traceback (most recent call last): File "~/FYP_Tests/FYP_Tests.py", line 140, in <module> print student File "/~FYP_Tests/Parties.py", line 30, in __str__ return "%s %s" %(self.id, self.name) File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/attributes.py", line 158, in __get__ return self.impl.get(instance_state(instance), instance_dict(instance)) AttributeError: 'NoneType' object has no attribute 'get' I'm at a loss as to how to resolve this issue, if it is an issue. If more information is required, please ask and I will provide it.

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• Creating self-referential tables with polymorphism in SQLALchemy

  - by Jace

  I'm trying to create a db structure in which I have many types of content entities, of which one, a Comment, can be attached to any other. Consider the following: from datetime import datetime from sqlalchemy import create_engine from sqlalchemy import Column, ForeignKey from sqlalchemy import Unicode, Integer, DateTime from sqlalchemy.orm import relation, backref from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Entity(Base): __tablename__ = 'entities' id = Column(Integer, primary_key=True) created_at = Column(DateTime, default=datetime.utcnow, nullable=False) edited_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False) type = Column(Unicode(20), nullable=False) __mapper_args__ = {'polymorphic_on': type} # <...insert some models based on Entity...> class Comment(Entity): __tablename__ = 'comments' __mapper_args__ = {'polymorphic_identity': u'comment'} id = Column(None, ForeignKey('entities.id'), primary_key=True) _idref = relation(Entity, foreign_keys=id, primaryjoin=id == Entity.id) attached_to_id = Column(Integer, ForeignKey('entities.id'), nullable=False) #attached_to = relation(Entity, remote_side=[Entity.id]) attached_to = relation(Entity, foreign_keys=attached_to_id, primaryjoin=attached_to_id == Entity.id, backref=backref('comments', cascade="all, delete-orphan")) text = Column(Unicode(255), nullable=False) engine = create_engine('sqlite://', echo=True) Base.metadata.bind = engine Base.metadata.create_all(engine) This seems about right, except SQLAlchemy doesn't like having two foreign keys pointing to the same parent. It says ArgumentError: Can't determine join between 'entities' and 'comments'; tables have more than one foreign key constraint relationship between them. Please specify the 'onclause' of this join explicitly. How do I specify onclause?

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• Setting up relations/mappings for a SQLAlchemy many-to-many database

  - by Brent Ramerth

  I'm new to SQLAlchemy and relational databases, and I'm trying to set up a model for an annotated lexicon. I want to support an arbitrary number of key-value annotations for the words which can be added or removed at runtime. Since there will be a lot of repetition in the names of the keys, I don't want to use this solution directly, although the code is similar. My design has word objects and property objects. The words and properties are stored in separate tables with a property_values table that links the two. Here's the code: from sqlalchemy import Column, Integer, String, Table, create_engine from sqlalchemy import MetaData, ForeignKey from sqlalchemy.orm import relation, mapper, sessionmaker from sqlalchemy.ext.declarative import declarative_base engine = create_engine('sqlite:///test.db', echo=True) meta = MetaData(bind=engine) property_values = Table('property_values', meta, Column('word_id', Integer, ForeignKey('words.id')), Column('property_id', Integer, ForeignKey('properties.id')), Column('value', String(20)) ) words = Table('words', meta, Column('id', Integer, primary_key=True), Column('name', String(20)), Column('freq', Integer) ) properties = Table('properties', meta, Column('id', Integer, primary_key=True), Column('name', String(20), nullable=False, unique=True) ) meta.create_all() class Word(object): def __init__(self, name, freq=1): self.name = name self.freq = freq class Property(object): def __init__(self, name): self.name = name mapper(Property, properties) Now I'd like to be able to do the following: Session = sessionmaker(bind=engine) s = Session() word = Word('foo', 42) word['bar'] = 'yes' # or word.bar = 'yes' ? s.add(word) s.commit() Ideally this should add 1|foo|42 to the words table, add 1|bar to the properties table, and add 1|1|yes to the property_values table. However, I don't have the right mappings and relations in place to make this happen. I get the sense from reading the documentation at http://www.sqlalchemy.org/docs/05/mappers.html#association-pattern that I want to use an association proxy or something of that sort here, but the syntax is unclear to me. I experimented with this: mapper(Word, words, properties={ 'properties': relation(Property, secondary=property_values) }) but this mapper only fills in the foreign key values, and I need to fill in the other value as well. Any assistance would be greatly appreciated.

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• Problem with between join for sqlalchemy orm relation.

  - by Gary van der Merwe

  I'm trying to create a relation that has a between join. Here is a shortish example of what I'm trying to do: #!/usr/bin/env python import sqlalchemy as sa from sqlalchemy import orm from sqlalchemy.engine.base import Engine from sqlalchemy.ext.declarative import declarative_base metadata = sa.MetaData() Base = declarative_base(metadata=metadata) engine = sa.create_engine('sqlite:///:memory:') class Network(Base): __tablename__ = "network" id = sa.Column(sa.Integer, primary_key=True) ip_net_addr_db = sa.Column('ip_net_addr', sa.Integer, index=True) ip_broadcast_addr_db = sa.Column('ip_broadcast_addr', sa.Integer, index=True) # This can be determined from the net address and the net mask, but we store # it in the db so that we can join with the address table. ip_net_mask_len = sa.Column(sa.SmallInteger) class Address(Base): __tablename__ = "address" ip_addr_db = sa.Column('ip_addr', sa.Integer, primary_key=True, index=True, unique=True) Network.addresses = orm.relation(Address, primaryjoin=Address.ip_addr_db.between( Network.ip_net_addr_db, Network.ip_broadcast_addr_db), foreign_keys=[Address.ip_addr_db]) metadata.create_all(engine) Session = orm.sessionmaker(bind=engine) Network() I you run this, you get this error: ArgumentError: Could not determine relation direction for primaryjoin condition 'address.ip_addr BETWEEN network.ip_net_addr AND network.ip_broadcast_addr', on relation Network.addresses. Do the columns in 'foreign_keys' represent only the 'foreign' columns in this join condition ? The answer to that question is Yes, but I cant figure out how to tell it that

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• Importing fixtures with foreign keys and SQLAlchemy?

  - by Chris Reid

  I've been experimenting with using fixture to load test data sets into my Pylons / PostgreSQL app. This works great except that it fails to properly create foreign keys if they reference an auto increment id field. My fixture looks like this: class AuthorsData(DataSet): class frank_herbert: first_name = "Frank" last_name = "Herbert" class BooksData(DataSet): class dune: title = "Dune" author_id = AuthorsData.frank_herbert.ref('id') And the model: t_authors = sa.Table("authors", meta.metadata, sa.Column("id", sa.types.Integer, primary_key=True), sa.Column("first_name", sa.types.String(100)), sa.Column("last_name", sa.types.String(100)), ) t_books = sa.Table("books", meta.metadata, sa.Column("id", sa.types.Integer, primary_key=True), sa.Column("title", sa.types.String(100)), sa.Column("author_id", sa.types.Integer, sa.ForeignKey('authors.id')) ) When running "paster setup-app development.ini", SQLAlchemey reports the FK value as "None" so it's obviously not finding it: 15:59:48,683 INFO [sqlalchemy.engine.base.Engine.0x...9eb0] INSERT INTO books (title, author_id) VALUES (%(title)s, %(author_id)s) RETURNING books.id 15:59:48,683 INFO [sqlalchemy.engine.base.Engine.0x...9eb0] {'author_id': None, 'title': 'Dune'} The fixture docs actually warn that this might be a problem: "However, in some cases you may need to reference an attribute that does not have a value until it is loaded, like a serial ID column. (Note that this is not supported by the SQLAlchemy data layer when using sessions.)" http://farmdev.com/projects/fixture/using-dataset.html#referencing-foreign-dataset-classes Does this mean that this is just not supported with SQLAlchemy? Or is it possible to load the data without using SA "sessions"? How are other people handling this issue?

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• how do simple SQLAlchemy relationships work?

  - by Carson Myers

  I'm no database expert -- I just know the basics, really. I've picked up SQLAlchemy for a small project, and I'm using the declarative base configuration rather than the "normal" way. This way seems a lot simpler. However, while setting up my database schema, I realized I don't understand some database relationship concepts. If I had a many-to-one relationship before, for example, articles by authors (where each article could be written by only a single author), I would put an author_id field in my articles column. But SQLAlchemy has this ForeignKey object, and a relationship function with a backref kwarg, and I have no idea what any of it MEANS. I'm scared to find out what a many-to-many relationship with an intermediate table looks like (when I need additional data about each relationship). Can someone demystify this for me? Right now I'm setting up to allow openID auth for my application. So I've got this: from __init__ import Base from sqlalchemy.schema import Column from sqlalchemy.types import Integer, String class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) username = Column(String, unique=True) email = Column(String) password = Column(String) salt = Column(String) class OpenID(Base): __tablename__ = 'openid' url = Column(String, primary_key=True) user_id = #? I think the ? should be replaced by Column(Integer, ForeignKey('users.id')), but I'm not sure -- and do I need to put openids = relationship("OpenID", backref="users") in the Users class? Why? What does it do? What is a backref?

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• getting last insert id .sqlalchemy orm

  - by gummmibear

  Hi i use sqlalchemy, i need some help. import hashlib import sqlalchemy as sa from sqlalchemy import orm from allsun.model import meta t_user = sa.Table("users",meta.metadata,autoload=True) class Duplicat(Exception): pass class LoginExistsException(Exception): pass class EmailExistsException(Exception): pass class User(object): """ def __setattr__(self, key, value): if key=='password' : value=unicode(hashlib.sha512(value).hexdigset()) object.__setattr__(self,key,value) """ def loginExists(self): try: meta.Session.query(User).filter(User.login==self.login).one() except orm.exc.NoResultFound: pass else: raise LoginExistsException() def emailExists(self): try: meta.Session.query(User).filter(User.email==self.email).one() except orm.exc.NoResultFound: pass else: raise EmailExistsException() def save(self): meta.Session.begin() meta.Session.save(self) try: meta.Session.commit() except sa.exc.IntegrityError: raise Duplicat() How can i get inserted id when i call? user = User() user.login = request.params['login'] user.password = hashlib.sha512(request.params['password']).hexdigest() user.email = request.params['email'] user.save()

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• dump csv from sqlalchemy

  - by afilatun

  For some reason, I want to dump a table from a database (sqlite3) in the form of a csv file. I'm using a python script with elixir (based on sqlalchemy) to modify the database. I was wondering if there is any way to dump the table I use to csv. I've seen sqlalchemy serializer but it doesn't seem to be what I want. Am I doing it wrong? Should I call the sqlite3 python module after closing my sqlalchemy session to dump to a file instead? Or should I use something homemade?

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• How to create a backup from SqlAlchemy?

  - by swilliams

  I'm writing a Pylons app, and am trying to create a simple backup system where every table is serialized and tarred up into a single file for an administrator to download, and use to restore the app should something bad happen. I can serialize my table data just fine using the SqlAlchemy serializer, and I can deserialize it fine as well, but I can't figure out how to commit those changes back to the database. In order to serialize my data I am doing this: from myproject.model.meta import Session from sqlalchemy.ext.serializer import loads, dumps q = Session.query(MyTable) serialized_data = dumps(q.all()) In order to test things out, I go ahead and truncation MyTable, and then attempt to restore using serialized_data: from myproject.model import meta restore_q = loads(serialized_data, meta.metadata, Session) This doesn't seem to do anything... I've tried calling a Session.commit after the fact, individually walking through all the objects in restore_q and adding them, but nothing seems to work. What am I missing? Or is there a better way to do what I'm aiming for? I don't want to shell out and directly touch the database, since SqlAlchemy supports different database engines.

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• SQLAlchemy automatically converts str to unicode on commit

  - by Victor Stanciu

  Hello, When inserting an object into a database with SQLAlchemy, all it's properties that correspond to String() columns are automatically transformed from <type 'str'> to <type 'unicode'>. Is there a way to prevent this behavior? Here is the code: from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData from sqlalchemy.orm import mapper, sessionmaker engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() table = Table('projects', metadata, Column('id', Integer, primary_key=True), Column('name', String(50)) ) class Project(object): def __init__(self, name): self.name = name mapper(Project, table) metadata.create_all(engine) session = sessionmaker(bind=engine)() project = Project("Lorem ipsum") print(type(project.name)) session.add(project) session.commit() print(type(project.name)) And here is the output: <type 'str'> <type 'unicode'> I know I should probably just work with unicode, but this would involve digging through some third-party code and I don't have the Python skills for that yet :)

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• How to get current date and time from DB using SQLAlchemy

  - by bluish

  I need to retrieve what's the current date and time for the database I'm connected with SQLAlchemy (not date and time of the machine where I'm running Python code). I've seen this functions, but they don't seem to do what they say: >>> from sqlalchemy import * >>> print func.current_date() CURRENT_DATE >>> print func.current_timestamp() CURRENT_TIMESTAMP Moreover it seems they don't need to be binded to any SQLAlchemy session or engine. It makes no sense... Thanks!

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• With sqlalchemy how to dynamically bind to database engine on a per-request basis

  - by Peter Hansen

  I have a Pylons-based web application which connects via Sqlalchemy (v0.5) to a Postgres database. For security, rather than follow the typical pattern of simple web apps (as seen in just about all tutorials), I'm not using a generic Postgres user (e.g. "webapp") but am requiring that users enter their own Postgres userid and password, and am using that to establish the connection. That means we get the full benefit of Postgres security. Complicating things still further, there are two separate databases to connect to. Although they're currently in the same Postgres cluster, they need to be able to move to separate hosts at a later date. We're using sqlalchemy's declarative package, though I can't see that this has any bearing on the matter. Most examples of sqlalchemy show trivial approaches such as setting up the Metadata once, at application startup, with a generic database userid and password, which is used through the web application. This is usually done with Metadata.bind = create_engine(), sometimes even at module-level in the database model files. My question is, how can we defer establishing the connections until the user has logged in, and then (of course) re-use those connections, or re-establish them using the same credentials, for each subsequent request. We have this working -- we think -- but I'm not only not certain of the safety of it, I also think it looks incredibly heavy-weight for the situation. Inside the __call__ method of the BaseController we retrieve the userid and password from the web session, call sqlalchemy create_engine() once for each database, then call a routine which calls Session.bind_mapper() repeatedly, once for each table that may be referenced on each of those connections, even though any given request usually references only one or two tables. It looks something like this: # in lib/base.py on the BaseController class def __call__(self, environ, start_response): # note: web session contains {'username': XXX, 'password': YYY} url1 = 'postgres://%(username)s:%(password)s@server1/finance' % session url2 = 'postgres://%(username)s:%(password)s@server2/staff' % session finance = create_engine(url1) staff = create_engine(url2) db_configure(staff, finance) # see below ... etc # in another file Session = scoped_session(sessionmaker()) def db_configure(staff, finance): s = Session() from db.finance import Employee, Customer, Invoice for c in [ Employee, Customer, Invoice, ]: s.bind_mapper(c, finance) from db.staff import Project, Hour for c in [ Project, Hour, ]: s.bind_mapper(c, staff) s.close() # prevents leaking connections between sessions? So the create_engine() calls occur on every request... I can see that being needed, and the Connection Pool probably caches them and does things sensibly. But calling Session.bind_mapper() once for each table, on every request? Seems like there has to be a better way. Obviously, since a desire for strong security underlies all this, we don't want any chance that a connection established for a high-security user will inadvertently be used in a later request by a low-security user.

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• Schema qualified tables with SQLAlchemy, SQLite and Postgresql?

  - by Chris Reid

  I have a Pylons project and a SQLAlchemy model that implements schema qualified tables: class Hockey(Base): __tablename__ = "hockey" __table_args__ = {'schema':'winter'} hockey_id = sa.Column(sa.types.Integer, sa.Sequence('score_id_seq', optional=True), primary_key=True) baseball_id = sa.Column(sa.types.Integer, sa.ForeignKey('summer.baseball.baseball_id')) This code works great with Postgresql but fails when using SQLite on table and foreign key names (due to SQLite's lack of schema support) sqlalchemy.exc.OperationalError: (OperationalError) unknown database "winter" 'PRAGMA "winter".table_info("hockey")' () I'd like to continue using SQLite for dev and testing. Is there a way of have this fail gracefully on SQLite?

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• Sqlite / SQLAlchemy: how to enforce Foreign Keys?

  - by Nick Perkins

  The new version of SQLite has the ability to enforce Foreign Key constraints, but for the sake of backwards-compatibility, you have to turn it on for each database connection separately! sqlite> PRAGMA foreign_keys = ON; I am using SQLAlchemy -- how can I make sure this always gets turned on? What I have tried is this: engine = sqlalchemy.create_engine('sqlite:///:memory:', echo=True) engine.execute('pragma foreign_keys=on') ...but it is not working!...What am I missing?

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• Fabfile with support for sqlalchemy-migrate deployments?

  - by Chris Reid

  I have database migrations (with sqlalchemy-migrate) working well in my dev environment. However, I'm a little stumped about how to integrate this into my deployment process. I'm using fabric for deployment but having some trouble scripting the migrations part. The path to the to migrations directory in site-packages is dynamic (due to changing egg version number) and I'd rather not hard code my db password into the fabfile. Does anyone have a fabfile that plays nicely with sqlalchemy-migrate?

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• Case insensitive string columns in SQLAlchemy?

  - by Timmy

  can i create a case insensitive string column in sqlalchemy? im using sqlite, and theres probaby a way to do it through DB by changing collation, but i want to keep it in sqlalchemy/python.

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• Using sqlalchemy to query using multiple column where in clause

  - by crunkchitis

  I'm looking to execute this query using sqlalchemy. SELECT name, age, favorite_color, favorite_food FROM kindergarten_classroom WHERE (favorite_color, favorite_food) IN (('lavender','lentil soup'),('black','carrot juice')); I only want kids that like (lavender AND lentil soup) OR (black and carrot juice). This is similar, but doesn't get me all of the way there: Sqlalchemy in clause

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