On Mon, Apr 30, 2018 at 4:18 PM, Derek Lambert
<dlamb...@dereklambert.com> wrote:
>>
>> mmm what do you mean by "mixin" here, it looks like every class you
>> have is mapped.
>>
>
> They are mapped in the code, but that's only so I can query them. I
> attempted to make LdapEntry and ActiveDirectoryEntry true mixin's by setting
> __abstract__ = True.
>
>>
>>
>> this a heavy set of inheritance and I might also use composition
>> instead, though that would change your DB design.
>>
>
> The design isn't in production yet so now would be the time to change it.
> Are you aware of any SQLAlchemy projects using composition I could review?
mmm not specifically, it means you might do something like store
"Entry" concepts in one table and "User" concepts in another.
looking more closely this seems like it would be akward also.
looking more closely at your mappings it looks like only
DirectoryEntry and DirectoryUser actually have any columns. The rest
is all synonyms. I'd likely use mixins for all those synonym sets.
>
> Thanks,
> Derek
>
> On Monday, April 30, 2018 at 1:30:51 PM UTC-5, Mike Bayer wrote:
>>
>> On Mon, Apr 30, 2018 at 1:33 PM, Derek Lambert
>> <dlam...@dereklambert.com> wrote:
>> > I'm running into an issue in a hierarchy of single-table inheritance
>> > objects
>> > with multiple inheritance. The objects represent users/groups/etc. from
>> > various directories and applications.
>> >
>> > Retrieving the list of synonyms from an object at the bottom of the
>> > inheritance tree doesn't return the entire list of synonyms.
>> >
>> > When I make some of the "mixin" type objects abstract the synonyms
>> > returned
>> > are as expected, but I lose the ability to query those objects.
>>
>> mmm what do you mean by "mixin" here, it looks like every class you
>> have is mapped.
>>
>> I will say that what you are doing here:
>>
>> class LdapUser(DirectoryUser, LdapEntry):
>> givenName = orm.synonym('first_name')
>> sn = orm.synonym('last_name')
>> __mapper_args__ = {
>> 'polymorphic_identity': 'ldap_user',
>> }
>>
>> where DirectoryUser and LdapEntry are also both mapped, I'm amazed
>> that even works. That's not at all anything that has ever been
>> supported or attempted, as each mapper only "inherits" from at most
>> one mapped class - while declarative supports actual "mixin" classes,
>> where by "mixin" we mean "non-mapped class", nothing in SQLAlchemy ORM
>> is expecting multiple inheritance at the mapper level. Above, I
>> guess it's picking one superclass mapper at random to be "inherits",
>> an ignoring the other, and that is likely the source of your issue.
>> Unfortunately I think you have to work out this hierarchy in terms of
>> single-inhertanace for classes that are actually mapped, which means
>> adding some non-mapped "mixin" classes that just accommodate for the
>> extra synonyms, something like:
>>
>> class DirectoryEntry(Base):
>>
>> class AbstractDirectoryUser(object):
>> # synonyms
>>
>> class DirectoryUser(AbstractDirectoryUser, DirectoryEntry):
>>
>> class LdapEntry(DirectoryEntry):
>>
>> class LdapUser(AbstractDirectoryUser, LdapEntry):
>>
>> this a heavy set of inheritance and I might also use composition
>> instead, though that would change your DB design.
>>
>>
>> >
>> > Maybe I'm overlooking a simpler implementation, or simply using
>> > SQLAlchemy
>> > in a way that wasn't intended?
>> >
>> > Here's a simplified subset of the code. In practice any object ending
>> > with
>> > Entry and the base DirectoryUser and DirectoryGroup wouldn't be created.
>> >
>> > import sqlalchemy as sa
>> > import sqlalchemy.orm as orm
>> > from sqlalchemy.ext.declarative import declarative_base
>> >
>> >
>> > Base = declarative_base()
>> >
>> >
>> > class DirectoryEntry(Base):
>> > guid = sa.Column(sa.Integer, primary_key=True)
>> > _type = sa.Column(sa.String, nullable=False,
>> > index=True)
>> > distinguished_name = sa.Column(sa.String, index=True)
>> > name = sa.Column(sa.String, index=True)
>> >
>> > __tablename__ = 'directory_entry'
>> > __mapper_args__ = {
>> > 'polymorphic_on': _type,
>> > 'polymorphic_identity': 'directory_entry',
>> > }
>> >
>> >
>> > class DirectoryUser(DirectoryEntry):
>> > first_name = sa.Column(sa.String)
>> > last_name = sa.Column(sa.String)
>> > email = sa.Column(sa.String)
>> > username = sa.Column(sa.String)
>> >
>> > __mapper_args__ = {
>> > 'polymorphic_identity': 'directory_user',
>> > }
>> >
>> >
>> > class LdapEntry(DirectoryEntry):
>> > cn = orm.synonym('name')
>> >
>> > __mapper_args__ = {
>> > 'polymorphic_identity': 'ldap_entry',
>> > }
>> >
>> >
>> > class LdapUser(DirectoryUser, LdapEntry):
>> > givenName = orm.synonym('first_name')
>> > sn = orm.synonym('last_name')
>> >
>> > __mapper_args__ = {
>> > 'polymorphic_identity': 'ldap_user',
>> > }
>> >
>> >
>> > class ActiveDirectoryEntry(LdapEntry):
>> > distinguishedName = orm.synonym('distinguished_name')
>> >
>> > __mapper_args__ = {
>> > 'polymorphic_identity': 'active_directory_entry',
>> > }
>> >
>> >
>> > class ActiveDirectoryUser(LdapUser, ActiveDirectoryEntry):
>> > mail = orm.synonym('email')
>> > sAMAccountName = orm.synonym('username')
>> >
>> > __mapper_args__ = {
>> > 'polymorphic_identity': 'active_directory_user'
>> > }
>> >
>> >
>> > engine_url = 'postgresql+psycopg2://postgres@localhost/inherit_test'
>> > engine = sa.create_engine(engine_url, echo=True)
>> >
>> > Base.metadata.create_all(engine)
>> >
>> > session = orm.sessionmaker(bind=engine)()
>> > ad_user = ActiveDirectoryUser(
>> > cn='John Doe',
>> > sAMAccountName='jdoe',
>> > distinguishedName='ou=domain',
>> > givenName='John'
>> > )
>> >
>> > session.add(ad_user)
>> > session.commit()
>> >
>> > user1 = session.query(DirectoryUser).filter(DirectoryUser.username ==
>> > 'jdoe').one()
>> > user3 = session.query(LdapUser).filter(LdapUser.username ==
>> > 'jdoe').one()
>> > user2 =
>> > session.query(ActiveDirectoryUser).filter(ActiveDirectoryUser.username
>> > ==
>> > 'jdoe').one()
>> > user4 = session.query(DirectoryEntry).filter(DirectoryEntry.name ==
>> > 'John
>> > Doe').one()
>> >
>> > assert(user1 == user2 == user3 == user4)
>> >
>> > mapper = sa.inspect(ad_user.__class__)
>> > synonyms = mapper.synonyms.keys()
>> >
>> > assert(synonyms == ['mail', 'sAMAccountName', 'givenName', 'sn', 'cn',
>> > 'distinguishedName'])
>> >
>> >
>> > Any help is appreciated!
>> >
>> > --
>> > 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 Example. See http://stackoverflow.com/help/mcve for a full
>> > description.
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> --
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> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
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http://www.sqlalchemy.org/
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