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from sqlalchemy import objectstore, create_engine, assign_mapper, relation, mapper, join
from sqlalchemy import and_, or_
from sqlalchemy import Table, Column, ForeignKey
from sqlalchemy.ext.proxy import ProxyEngine
import inspect
import sys
#
# the "proxy" to the database engine... this can be swapped out at runtime
#
engine = ProxyEngine()
#
# declarative column declaration - this is so that we can infer the colname
#
class column(object):
def __init__(self, coltype, colname=None, foreign_key=None,
primary_key=False, *args, **kwargs):
if isinstance( foreign_key, basestring ):
foreign_key= ForeignKey( foreign_key )
self.coltype = coltype
self.colname = colname
self.foreign_key = foreign_key
self.primary_key = primary_key
self.kwargs = kwargs
self.args = args
#
# declarative relationship declaration
#
class relationship(object):
def __init__(self, classname, colname=None, backref=None, private=False,
lazy=True, uselist=True, secondary=None):
self.classname = classname
self.colname = colname
self.backref = backref
self.private = private
self.lazy = lazy
self.uselist = uselist
self.secondary = secondary
class one_to_many(relationship):
def __init__(self, classname, colname=None, backref=None, private=False, lazy=True):
relationship.__init__(self, classname, colname, backref, private, lazy, uselist=True)
class one_to_one(relationship):
def __init__(self, classname, colname=None, backref=None, private=False, lazy=True):
relationship.__init__(self, classname, colname, backref, private, lazy, uselist=False)
class many_to_many(relationship):
def __init__(self, classname, secondary, backref=None, lazy=True):
relationship.__init__(self, classname, None, backref, False, lazy,
uselist=True, secondary=secondary)
#
# SQLAlchemy metaclass and superclass that can be used to do SQLAlchemy
# mapping in a declarative way, along with a function to process the
# relationships between dependent objects as they come in, without blowing
# up if the classes aren't specified in a proper order
#
__deferred_classes__ = []
__processed_classes__ = []
def check_relationships(klass):
#Check the class for foreign_keys recursively. If some foreign table is not found, the processing of the table
#must be defered.
for keyname in klass.table._foreign_keys:
xtable = keyname._colspec[:keyname._colspec.find('.')]
tablefound = False
for xclass in ActiveMapperMeta.classes:
if ActiveMapperMeta.classes[xclass].table.from_name == xtable:
tablefound = True
break
if tablefound==False:
#The refered table has not yet been created.
return False
return True
def process_relationships(klass):
defer = False
for propname, reldesc in klass.relations.items():
#We require that every related table has been processed first
if not reldesc.classname in __processed_classes__:
if not klass._classname in __deferred_classes__: __deferred_classes__.append(klass._classname)
defer = True
#Check every column item to see if it points to an existing table
#if it does not, defer...
if not defer:
if not check_relationships(klass):
if not klass._classname in __deferred_classes__: __deferred_classes__.append(klass._classname)
defer = True
if not defer:
relations = {}
__processed_classes__.append(klass._classname)
for propname, reldesc in klass.relations.items():
relclass = ActiveMapperMeta.classes[reldesc.classname]
relations[propname] = relation(relclass.mapper,
secondary=reldesc.secondary,
backref=reldesc.backref,
private=reldesc.private,
lazy=reldesc.lazy,
uselist=reldesc.uselist)
if len(relations)>0:
assign_mapper(klass, klass.table, properties=relations)
if klass._classname in __deferred_classes__: __deferred_classes__.remove(klass._classname)
for deferred_class in __deferred_classes__:
process_relationships(ActiveMapperMeta.classes[deferred_class])
class ActiveMapperMeta(type):
classes = {}
def __init__(cls, clsname, bases, dict):
table_name = clsname.lower()
columns = []
relations = {}
_engine = getattr( sys.modules[cls.__module__], "__engine__", engine )
if 'mapping' in dict:
members = inspect.getmembers(dict.get('mapping'))
for name, value in members:
if name == '__table__':
table_name = value
continue
if '__engine__' == name:
_engine= value
continue
if name.startswith('__'): continue
if isinstance(value, column):
if value.foreign_key:
col = Column(value.colname or name,
value.coltype,
value.foreign_key,
primary_key=value.primary_key,
*value.args, **value.kwargs)
else:
col = Column(value.colname or name,
value.coltype,
primary_key=value.primary_key,
*value.args, **value.kwargs)
columns.append(col)
continue
if isinstance(value, relationship):
relations[name] = value
assert _engine is not None, "No engine specified"
cls.table = Table(table_name, _engine, *columns)
# check for inheritence
if hasattr( bases[0], "mapping" ):
cls._base_mapper= bases[0].mapper
assign_mapper(cls, cls.table, inherits=cls._base_mapper)
else:
assign_mapper(cls, cls.table)
cls.relations = relations
cls._classname = clsname
ActiveMapperMeta.classes[clsname] = cls
process_relationships(cls)
super(ActiveMapperMeta, cls).__init__(clsname, bases, dict)
class ActiveMapper(object):
__metaclass__ = ActiveMapperMeta
def set(self, **kwargs):
for key, value in kwargs.items():
setattr(self, key, value)
#
# a utility function to create all tables for all ActiveMapper classes
#
def create_tables():
for klass in ActiveMapperMeta.classes.values():
klass.table.create()
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