Hi All,
I have created a base declarative object that has a pre-made primary
key, so I don't have to add it to all my child tables:
class ClassDefaults(DeclarativeMeta):
def __init__(cls,classname, bases, dict_):
dict_['id'] = Column(Integer, Sequence("id_seq",
optional=True), primary_key=True)
return DeclarativeMeta.__init__(cls, classname, bases, dict_)
Base = declarative_base(metaclass=ClassDefaults)
This allows me to create a table as follows, and have an implicit
primary key named "id":
class UserGroup(Base):
__tablename__ = 'usergroup'
name = Column(String(80), nullable=False, unique=True, index=True)
However, my base class currently uses the *same* sequence for all
primary keys. I would like to create a new sequence for each primary
key. I was thinking of naming the sequence based on the name of the
table, so that UserGroup's sequence would be called
"usergroup_id_seq", etc.
I am wondering how this is possible, using the above approach, or
using Mix-ins, as documented here (Michael Bayer pointed me in this
direction) --
http://www.sqlalchemy.org/docs/reference/ext/declarative.html#mix-in-classes
While mix-ins look cool, I am not sure how I would reference the
__tablename__ of the child class from the Mixin.
I can probably work around this by *not* naming the sequences after
the table name, but instead use an incrementing global variable to
create the unique sequence names, but it seems like a better practice
to base the sequence name on the name of the table itself.
Michael says that Chris Withers may know how to do this with Mix-ins.
Chris, you out there? :)
Regards,
Daniel
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