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# mapper/__init__.py
# Copyright (C) 2005,2006 Michael Bayer mike_mp@zzzcomputing.com
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""
the mapper package provides object-relational functionality, building upon the schema and sql
packages and tying operations to class properties and constructors.
"""
import sqlalchemy.sql as sql
import sqlalchemy.schema as schema
import sqlalchemy.engine as engine
import sqlalchemy.util as util
import objectstore
import types as types
from mapper import *
from properties import *
import mapper as mapperlib
__all__ = ['relation', 'eagerload', 'lazyload', 'noload', 'deferred', 'defer', 'undefer',
'mapper', 'clear_mappers', 'objectstore', 'sql', 'extension', 'class_mapper', 'object_mapper', 'MapperExtension',
'assign_mapper'
]
def relation(*args, **kwargs):
"""provides a relationship of a primary Mapper to a secondary Mapper, which corresponds
to a parent-child or associative table relationship."""
if len(args) > 1 and isinstance(args[0], type):
raise ValueError("relation(class, table, **kwargs) is deprecated. Please use relation(class, **kwargs) or relation(mapper, **kwargs).")
return _relation_loader(*args, **kwargs)
def _relation_loader(mapper, secondary=None, primaryjoin=None, secondaryjoin=None, lazy=True, **kwargs):
if lazy:
return LazyLoader(mapper, secondary, primaryjoin, secondaryjoin, **kwargs)
elif lazy is None:
return PropertyLoader(mapper, secondary, primaryjoin, secondaryjoin, **kwargs)
else:
return EagerLoader(mapper, secondary, primaryjoin, secondaryjoin, **kwargs)
def deferred(*columns, **kwargs):
return DeferredColumnProperty(*columns, **kwargs)
def mapper(class_, table=None, *args, **params):
"""returns a new or already cached Mapper object."""
if table is None:
return class_mapper(class_)
return Mapper(class_, table, *args, **params)
def clear_mappers():
"""removes all mappers that have been created thus far. when new mappers are
created, they will be assigned to their classes as their primary mapper."""
mapper_registry.clear()
def clear_mapper(m):
"""removes the given mapper from the storage of mappers. when a new mapper is
created for the previous mapper's class, it will be used as that classes'
new primary mapper."""
del mapper_registry[m.hash_key]
def extension(ext):
"""returns a MapperOption that will add the given MapperExtension to the
mapper returned by mapper.options()."""
return ExtensionOption(ext)
def eagerload(name, **kwargs):
"""returns a MapperOption that will convert the property of the given name
into an eager load. Used with mapper.options()"""
return EagerLazyOption(name, toeager=True, **kwargs)
def lazyload(name, **kwargs):
"""returns a MapperOption that will convert the property of the given name
into a lazy load. Used with mapper.options()"""
return EagerLazyOption(name, toeager=False, **kwargs)
def noload(name, **kwargs):
"""returns a MapperOption that will convert the property of the given name
into a non-load. Used with mapper.options()"""
return EagerLazyOption(name, toeager=None, **kwargs)
def defer(name, **kwargs):
"""returns a MapperOption that will convert the column property of the given
name into a deferred load. Used with mapper.options()"""
return DeferredOption(name, defer=True)
def undefer(name, **kwargs):
"""returns a MapperOption that will convert the column property of the given
name into a non-deferred (regular column) load. Used with mapper.options."""
return DeferredOption(name, defer=False)
def object_mapper(object):
"""given an object, returns the primary Mapper associated with the object
or the object's class."""
return class_mapper(object.__class__)
def class_mapper(class_):
"""given a class, returns the primary Mapper associated with the class."""
return mapper_registry[class_]
try:
return mapper_registry[class_]
except KeyError:
pass
except AttributeError:
pass
raise "Class '%s' has no mapper associated with it" % class_.__name__
def assign_mapper(class_, *args, **params):
params.setdefault("is_primary", True)
if not isinstance(getattr(class_, '__init__'), types.MethodType):
def __init__(self, **kwargs):
for key, value in kwargs.items():
setattr(self, key, value)
class_.__init__ = __init__
m = mapper(class_, *args, **params)
class_.mapper = m
class_.get = m.get
class_.select = m.select
class_.select_by = m.select_by
class_.selectone = m.selectone
class_.get_by = m.get_by
def commit(self):
objectstore.commit(self)
def delete(self):
objectstore.delete(self)
class_.commit = commit
class_.delete = delete
def cascade_mappers(*classes_or_mappers):
"""given a list of classes and/or mappers, identifies the foreign key relationships
between the given mappers or corresponding class mappers, and creates relation()
objects representing those relationships, including a backreference. Attempts to find
the "secondary" table in a many-to-many relationship as well. The names of the relations
will be a lowercase version of the related class. In the case of one-to-many or many-to-many,
the name will be "pluralized", which currently is based on the English language (i.e. an 's' or
'es' added to it)."""
table_to_mapper = {}
for item in classes_or_mappers:
if isinstance(item, Mapper):
m = item
else:
klass = item
m = class_mapper(klass)
table_to_mapper[m.table] = m
def pluralize(name):
# oh crap, do we need locale stuff now
if name[-1] == 's':
return name + "es"
else:
return name + "s"
for table,mapper in table_to_mapper.iteritems():
for fk in table.foreign_keys:
if fk.column.table is table:
continue
secondary = None
try:
m2 = table_to_mapper[fk.column.table]
except KeyError:
if len(fk.column.table.primary_key):
continue
for sfk in fk.column.table.foreign_keys:
if sfk.column.table is table:
continue
m2 = table_to_mapper.get(sfk.column.table)
secondary = fk.column.table
if m2 is None:
continue
if secondary:
propname = pluralize(m2.class_.__name__.lower())
propname2 = pluralize(mapper.class_.__name__.lower())
else:
propname = m2.class_.__name__.lower()
propname2 = pluralize(mapper.class_.__name__.lower())
mapper.add_property(propname, relation(m2, secondary=secondary, backref=propname2))
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