1. Philip Jenvey
  2. sqlalchemy-cext_py3k

Source

sqlalchemy-cext_py3k / lib / sqlalchemy / orm / util.py

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# orm/util.py
# Copyright (C) 2005-2012 the SQLAlchemy authors and contributors <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php


from sqlalchemy import sql, util, event, exc as sa_exc
from sqlalchemy.sql import expression, util as sql_util, operators
from sqlalchemy.orm.interfaces import MapperExtension, EXT_CONTINUE,\
                                PropComparator, MapperProperty
from sqlalchemy.orm import attributes, exc
import operator
import re

mapperlib = util.importlater("sqlalchemy.orm", "mapperlib")

all_cascades = frozenset(("delete", "delete-orphan", "all", "merge",
                          "expunge", "save-update", "refresh-expire",
                          "none"))

_INSTRUMENTOR = ('mapper', 'instrumentor')

class CascadeOptions(frozenset):
    """Keeps track of the options sent to relationship().cascade"""

    _add_w_all_cascades = all_cascades.difference([
                            'all', 'none', 'delete-orphan'])
    _allowed_cascades = all_cascades

    def __new__(cls, arg):
        values = set([
                    c for c 
                    in re.split('\s*,\s*', arg or "")
                    if c
                ])

        if values.difference(cls._allowed_cascades):
            raise sa_exc.ArgumentError(
                    "Invalid cascade option(s): %s" % 
                    ", ".join([repr(x) for x in 
                        sorted(
                            values.difference(cls._allowed_cascades)
                    )])
            )

        if "all" in values:
            values.update(cls._add_w_all_cascades)
        if "none" in values:
            values.clear()
        values.discard('all')

        self = frozenset.__new__(CascadeOptions, values)
        self.save_update = 'save-update' in values
        self.delete = 'delete' in values
        self.refresh_expire = 'refresh-expire' in values
        self.merge = 'merge' in values
        self.expunge = 'expunge' in values
        self.delete_orphan = "delete-orphan" in values

        if self.delete_orphan and not self.delete:
            util.warn("The 'delete-orphan' cascade "
                        "option requires 'delete'.")
        return self

    def __repr__(self):
        return "CascadeOptions(%r)" % (
            ",".join([x for x in sorted(self)])
        )

def _validator_events(desc, key, validator):
    """Runs a validation method on an attribute value to be set or appended."""

    def append(state, value, initiator):
        return validator(state.obj(), key, value)

    def set_(state, value, oldvalue, initiator):
        return validator(state.obj(), key, value)

    event.listen(desc, 'append', append, raw=True, retval=True)
    event.listen(desc, 'set', set_, raw=True, retval=True)

def polymorphic_union(table_map, typecolname, aliasname='p_union', cast_nulls=True):
    """Create a ``UNION`` statement used by a polymorphic mapper.

    See  :ref:`concrete_inheritance` for an example of how
    this is used.
    
    :param table_map: mapping of polymorphic identities to 
     :class:`.Table` objects.
    :param typecolname: string name of a "discriminator" column, which will be 
     derived from the query, producing the polymorphic identity for each row.  If
     ``None``, no polymorphic discriminator is generated.
    :param aliasname: name of the :func:`~sqlalchemy.sql.expression.alias()` 
     construct generated.
    :param cast_nulls: if True, non-existent columns, which are represented as labeled
     NULLs, will be passed into CAST.   This is a legacy behavior that is problematic
     on some backends such as Oracle - in which case it can be set to False.

    """

    colnames = util.OrderedSet()
    colnamemaps = {}
    types = {}
    for key in table_map.keys():
        table = table_map[key]

        # mysql doesnt like selecting from a select; 
        # make it an alias of the select
        if isinstance(table, sql.Select):
            table = table.alias()
            table_map[key] = table

        m = {}
        for c in table.c:
            colnames.add(c.key)
            m[c.key] = c
            types[c.key] = c.type
        colnamemaps[table] = m

    def col(name, table):
        try:
            return colnamemaps[table][name]
        except KeyError:
            if cast_nulls:
                return sql.cast(sql.null(), types[name]).label(name)
            else:
                return sql.type_coerce(sql.null(), types[name]).label(name)

    result = []
    for type, table in table_map.iteritems():
        if typecolname is not None:
            result.append(
                    sql.select([col(name, table) for name in colnames] +
                    [sql.literal_column(sql_util._quote_ddl_expr(type)).
                            label(typecolname)],
                             from_obj=[table]))
        else:
            result.append(sql.select([col(name, table) for name in colnames],
                                     from_obj=[table]))
    return sql.union_all(*result).alias(aliasname)

def identity_key(*args, **kwargs):
    """Get an identity key.

    Valid call signatures:

    * ``identity_key(class, ident)``

      class
          mapped class (must be a positional argument)

      ident
          primary key, if the key is composite this is a tuple


    * ``identity_key(instance=instance)``

      instance
          object instance (must be given as a keyword arg)

    * ``identity_key(class, row=row)``

      class
          mapped class (must be a positional argument)

      row
          result proxy row (must be given as a keyword arg)

    """
    if args:
        if len(args) == 1:
            class_ = args[0]
            try:
                row = kwargs.pop("row")
            except KeyError:
                ident = kwargs.pop("ident")
        elif len(args) == 2:
            class_, ident = args
        elif len(args) == 3:
            class_, ident = args
        else:
            raise sa_exc.ArgumentError("expected up to three "
                "positional arguments, got %s" % len(args))
        if kwargs:
            raise sa_exc.ArgumentError("unknown keyword arguments: %s"
                % ", ".join(kwargs.keys()))
        mapper = class_mapper(class_)
        if "ident" in locals():
            return mapper.identity_key_from_primary_key(ident)
        return mapper.identity_key_from_row(row)
    instance = kwargs.pop("instance")
    if kwargs:
        raise sa_exc.ArgumentError("unknown keyword arguments: %s"
            % ", ".join(kwargs.keys()))
    mapper = object_mapper(instance)
    return mapper.identity_key_from_instance(instance)

class ORMAdapter(sql_util.ColumnAdapter):
    """Extends ColumnAdapter to accept ORM entities.

    The selectable is extracted from the given entity,
    and the AliasedClass if any is referenced.

    """
    def __init__(self, entity, equivalents=None, 
                            chain_to=None, adapt_required=False):
        self.mapper, selectable, is_aliased_class = _entity_info(entity)
        if is_aliased_class:
            self.aliased_class = entity
        else:
            self.aliased_class = None
        sql_util.ColumnAdapter.__init__(self, selectable, 
                                        equivalents, chain_to,
                                        adapt_required=adapt_required)

    def replace(self, elem):
        entity = elem._annotations.get('parentmapper', None)
        if not entity or entity.isa(self.mapper):
            return sql_util.ColumnAdapter.replace(self, elem)
        else:
            return None

class AliasedClass(object):
    """Represents an "aliased" form of a mapped class for usage with Query.

    The ORM equivalent of a :func:`sqlalchemy.sql.expression.alias`
    construct, this object mimics the mapped class using a
    __getattr__ scheme and maintains a reference to a
    real :class:`~sqlalchemy.sql.expression.Alias` object.

    Usage is via the :class:`~sqlalchemy.orm.aliased()` synonym::

        # find all pairs of users with the same name
        user_alias = aliased(User)
        session.query(User, user_alias).\\
                        join((user_alias, User.id > user_alias.id)).\\
                        filter(User.name==user_alias.name)
    
    The resulting object is an instance of :class:`.AliasedClass`, however
    it implements a ``__getattribute__()`` scheme which will proxy attribute
    access to that of the ORM class being aliased.  All classmethods
    on the mapped entity should also be available here, including 
    hybrids created with the :ref:`hybrids_toplevel` extension,
    which will receive the :class:`.AliasedClass` as the "class" argument
    when classmethods are called.
    
    :param cls: ORM mapped entity which will be "wrapped" around an alias.
    :param alias: a selectable, such as an :func:`.alias` or :func:`.select`
     construct, which will be rendered in place of the mapped table of the
     ORM entity.  If left as ``None``, an ordinary :class:`.Alias` of the 
     ORM entity's mapped table will be generated.
    :param name: A name which will be applied both to the :class:`.Alias`
     if one is generated, as well as the name present in the "named tuple"
     returned by the :class:`.Query` object when results are returned.
    :param adapt_on_names: if True, more liberal "matching" will be used when
     mapping the mapped columns of the ORM entity to those of the given selectable - 
     a name-based match will be performed if the given selectable doesn't 
     otherwise have a column that corresponds to one on the entity.  The 
     use case for this is when associating an entity with some derived
     selectable such as one that uses aggregate functions::
     
        class UnitPrice(Base):
            __tablename__ = 'unit_price'
            ...
            unit_id = Column(Integer)
            price = Column(Numeric)
        
        aggregated_unit_price = Session.query(
                                    func.sum(UnitPrice.price).label('price')
                                ).group_by(UnitPrice.unit_id).subquery()
                                
        aggregated_unit_price = aliased(UnitPrice, alias=aggregated_unit_price, adapt_on_names=True)
    
     Above, functions on ``aggregated_unit_price`` which
     refer to ``.price`` will return the
     ``fund.sum(UnitPrice.price).label('price')`` column,
     as it is matched on the name "price".  Ordinarily, the "price" function wouldn't
     have any "column correspondence" to the actual ``UnitPrice.price`` column
     as it is not a proxy of the original.
     
     ``adapt_on_names`` is new in 0.7.3.
        
    """
    def __init__(self, cls, alias=None, name=None, adapt_on_names=False):
        self.__mapper = _class_to_mapper(cls)
        self.__target = self.__mapper.class_
        self.__adapt_on_names = adapt_on_names
        if alias is None:
            alias = self.__mapper._with_polymorphic_selectable.alias(name=name)
        self.__adapter = sql_util.ClauseAdapter(alias,
                                equivalents=self.__mapper._equivalent_columns,
                                adapt_on_names=self.__adapt_on_names)
        self.__alias = alias
        # used to assign a name to the RowTuple object
        # returned by Query.
        self._sa_label_name = name
        self.__name__ = 'AliasedClass_' + str(self.__target)

    def __getstate__(self):
        return {
            'mapper':self.__mapper, 
            'alias':self.__alias, 
            'name':self._sa_label_name,
            'adapt_on_names':self.__adapt_on_names,
        }

    def __setstate__(self, state):
        self.__mapper = state['mapper']
        self.__target = self.__mapper.class_
        self.__adapt_on_names = state['adapt_on_names']
        alias = state['alias']
        self.__adapter = sql_util.ClauseAdapter(alias,
                                equivalents=self.__mapper._equivalent_columns,
                                adapt_on_names=self.__adapt_on_names)
        self.__alias = alias
        name = state['name']
        self._sa_label_name = name
        self.__name__ = 'AliasedClass_' + str(self.__target)

    def __adapt_element(self, elem):
        return self.__adapter.traverse(elem).\
                    _annotate({
                        'parententity': self, 
                        'parentmapper':self.__mapper}
                    )

    def __adapt_prop(self, existing, key):
        comparator = existing.comparator.adapted(self.__adapt_element)

        queryattr = attributes.QueryableAttribute(self, key,
            impl=existing.impl, parententity=self, comparator=comparator)
        setattr(self, key, queryattr)
        return queryattr

    def __getattr__(self, key):
        for base in self.__target.__mro__:
            try:
                attr = object.__getattribute__(base, key)
            except AttributeError:
                continue
            else:
                break
        else:
            raise AttributeError(key)

        if isinstance(attr, attributes.QueryableAttribute):
            return self.__adapt_prop(attr, key)
        elif hasattr(attr, 'func_code'):
            is_method = getattr(self.__target, key, None)
            if is_method and is_method.im_self is not None:
                return util.types.MethodType(attr.im_func, self, self)
            else:
                return None
        elif hasattr(attr, '__get__'):
            ret = attr.__get__(None, self)
            if isinstance(ret, PropComparator):
                return ret.adapted(self.__adapt_element)
            return ret
        else:
            return attr

    def __repr__(self):
        return '<AliasedClass at 0x%x; %s>' % (
            id(self), self.__target.__name__)

def aliased(element, alias=None, name=None, adapt_on_names=False):
    if isinstance(element, expression.FromClause):
        if adapt_on_names:
            raise sa_exc.ArgumentError("adapt_on_names only applies to ORM elements")
        return element.alias(name)
    else:
        return AliasedClass(element, alias=alias, name=name, adapt_on_names=adapt_on_names)

def _orm_annotate(element, exclude=None):
    """Deep copy the given ClauseElement, annotating each element with the
    "_orm_adapt" flag.

    Elements within the exclude collection will be cloned but not annotated.

    """
    return sql_util._deep_annotate(element, {'_orm_adapt':True}, exclude)

_orm_deannotate = sql_util._deep_deannotate

class _ORMJoin(expression.Join):
    """Extend Join to support ORM constructs as input."""

    __visit_name__ = expression.Join.__visit_name__

    def __init__(self, left, right, onclause=None, 
                            isouter=False, join_to_left=True):
        adapt_from = None

        if hasattr(left, '_orm_mappers'):
            left_mapper = left._orm_mappers[1]
            if join_to_left:
                adapt_from = left.right
        else:
            left_mapper, left, left_is_aliased = _entity_info(left)
            if join_to_left and (left_is_aliased or not left_mapper):
                adapt_from = left

        right_mapper, right, right_is_aliased = _entity_info(right)
        if right_is_aliased:
            adapt_to = right
        else:
            adapt_to = None

        if left_mapper or right_mapper:
            self._orm_mappers = (left_mapper, right_mapper)

            if isinstance(onclause, basestring):
                prop = left_mapper.get_property(onclause)
            elif isinstance(onclause, attributes.QueryableAttribute):
                if adapt_from is None:
                    adapt_from = onclause.__clause_element__()
                prop = onclause.property
            elif isinstance(onclause, MapperProperty):
                prop = onclause
            else:
                prop = None

            if prop:
                pj, sj, source, dest, \
                secondary, target_adapter = prop._create_joins(
                                source_selectable=adapt_from,
                                dest_selectable=adapt_to,
                                source_polymorphic=True,
                                dest_polymorphic=True,
                                of_type=right_mapper)

                if sj is not None:
                    left = sql.join(left, secondary, pj, isouter)
                    onclause = sj
                else:
                    onclause = pj
                self._target_adapter = target_adapter

        expression.Join.__init__(self, left, right, onclause, isouter)

    def join(self, right, onclause=None, isouter=False, join_to_left=True):
        return _ORMJoin(self, right, onclause, isouter, join_to_left)

    def outerjoin(self, right, onclause=None, join_to_left=True):
        return _ORMJoin(self, right, onclause, True, join_to_left)

def join(left, right, onclause=None, isouter=False, join_to_left=True):
    """Produce an inner join between left and right clauses.
    
    :func:`.orm.join` is an extension to the core join interface
    provided by :func:`.sql.expression.join()`, where the
    left and right selectables may be not only core selectable
    objects such as :class:`.Table`, but also mapped classes or
    :class:`.AliasedClass` instances.   The "on" clause can
    be a SQL expression, or an attribute or string name
    referencing a configured :func:`.relationship`.

    ``join_to_left`` indicates to attempt aliasing the ON clause,
    in whatever form it is passed, to the selectable
    passed as the left side.  If False, the onclause
    is used as is.
    
    :func:`.orm.join` is not commonly needed in modern usage,
    as its functionality is encapsulated within that of the
    :meth:`.Query.join` method, which features a
    significant amount of automation beyond :func:`.orm.join`
    by itself.  Explicit usage of :func:`.orm.join` 
    with :class:`.Query` involves usage of the 
    :meth:`.Query.select_from` method, as in::
    
        from sqlalchemy.orm import join
        session.query(User).\\
            select_from(join(User, Address, User.addresses)).\\
            filter(Address.email_address=='foo@bar.com')
    
    In modern SQLAlchemy the above join can be written more 
    succinctly as::
    
        session.query(User).\\
                join(User.addresses).\\
                filter(Address.email_address=='foo@bar.com')

    See :meth:`.Query.join` for information on modern usage
    of ORM level joins.
    
    """
    return _ORMJoin(left, right, onclause, isouter, join_to_left)

def outerjoin(left, right, onclause=None, join_to_left=True):
    """Produce a left outer join between left and right clauses.

    This is the "outer join" version of the :func:`.orm.join` function,
    featuring the same behavior except that an OUTER JOIN is generated.
    See that function's documentation for other usage details.

    """
    return _ORMJoin(left, right, onclause, True, join_to_left)

def with_parent(instance, prop):
    """Create filtering criterion that relates this query's primary entity
    to the given related instance, using established :func:`.relationship()`
    configuration.

    The SQL rendered is the same as that rendered when a lazy loader
    would fire off from the given parent on that attribute, meaning
    that the appropriate state is taken from the parent object in 
    Python without the need to render joins to the parent table
    in the rendered statement.

    As of 0.6.4, this method accepts parent instances in all 
    persistence states, including transient, persistent, and detached.
    Only the requisite primary key/foreign key attributes need to
    be populated.  Previous versions didn't work with transient
    instances.

    :param instance:
      An instance which has some :func:`.relationship`.

    :param property:
      String property name, or class-bound attribute, which indicates
      what relationship from the instance should be used to reconcile the 
      parent/child relationship. 

    """
    if isinstance(prop, basestring):
        mapper = object_mapper(instance)
        prop = getattr(mapper.class_, prop).property
    elif isinstance(prop, attributes.QueryableAttribute):
        prop = prop.property

    return prop.compare(operators.eq, 
                        instance, 
                        value_is_parent=True)


def _entity_info(entity, compile=True):
    """Return mapping information given a class, mapper, or AliasedClass.

    Returns 3-tuple of: mapper, mapped selectable, boolean indicating if this
    is an aliased() construct.

    If the given entity is not a mapper, mapped class, or aliased construct,
    returns None, the entity, False.  This is typically used to allow
    unmapped selectables through.

    """
    if isinstance(entity, AliasedClass):
        return entity._AliasedClass__mapper, entity._AliasedClass__alias, True

    if isinstance(entity, mapperlib.Mapper):
        mapper = entity

    elif isinstance(entity, type):
        class_manager = attributes.manager_of_class(entity)

        if class_manager is None:
            return None, entity, False

        mapper = class_manager.mapper
    else:
        return None, entity, False

    if compile and mapperlib.module._new_mappers:
        mapperlib.configure_mappers()
    return mapper, mapper._with_polymorphic_selectable, False

def _entity_descriptor(entity, key):
    """Return a class attribute given an entity and string name.

    May return :class:`.InstrumentedAttribute` or user-defined
    attribute.

    """
    if isinstance(entity, expression.FromClause):
        description = entity
        entity = entity.c
    elif not isinstance(entity, (AliasedClass, type)):
        description = entity = entity.class_
    else:
        description = entity

    try:
        return getattr(entity, key)
    except AttributeError:
        raise sa_exc.InvalidRequestError(
                    "Entity '%s' has no property '%s'" % 
                    (description, key)
                )

def _orm_columns(entity):
    mapper, selectable, is_aliased_class = _entity_info(entity)
    if isinstance(selectable, expression.Selectable):
        return [c for c in selectable.c]
    else:
        return [selectable]

def _orm_selectable(entity):
    mapper, selectable, is_aliased_class = _entity_info(entity)
    return selectable

def _attr_as_key(attr):
    if hasattr(attr, 'key'):
        return attr.key
    else:
        return expression._column_as_key(attr)

def _is_aliased_class(entity):
    return isinstance(entity, AliasedClass)

_state_mapper = util.dottedgetter('manager.mapper')

def object_mapper(instance):
    """Given an object, return the primary Mapper associated with the object
    instance.

    Raises UnmappedInstanceError if no mapping is configured.

    """
    try:
        state = attributes.instance_state(instance)
        return state.manager.mapper
    except exc.UnmappedClassError:
        raise exc.UnmappedInstanceError(instance)
    except exc.NO_STATE:
        raise exc.UnmappedInstanceError(instance)

def class_mapper(class_, compile=True):
    """Given a class, return the primary :class:`.Mapper` associated 
    with the key.

    Raises :class:`.UnmappedClassError` if no mapping is configured
    on the given class, or :class:`.ArgumentError` if a non-class
    object is passed.

    """

    try:
        class_manager = attributes.manager_of_class(class_)
        mapper = class_manager.mapper

    except exc.NO_STATE:
        if not isinstance(class_, type): 
            raise sa_exc.ArgumentError("Class object expected, got '%r'." % class_) 
        raise exc.UnmappedClassError(class_)

    if compile and mapperlib.module._new_mappers:
        mapperlib.configure_mappers()
    return mapper

def _class_to_mapper(class_or_mapper, compile=True):
    if _is_aliased_class(class_or_mapper):
        return class_or_mapper._AliasedClass__mapper

    elif isinstance(class_or_mapper, type):
        try:
            class_manager = attributes.manager_of_class(class_or_mapper)
            mapper = class_manager.mapper
        except exc.NO_STATE:
            raise exc.UnmappedClassError(class_or_mapper)
    elif isinstance(class_or_mapper, mapperlib.Mapper):
        mapper = class_or_mapper
    else:
        raise exc.UnmappedClassError(class_or_mapper)

    if compile and mapperlib.module._new_mappers:
        mapperlib.configure_mappers()
    return mapper

def has_identity(object):
    state = attributes.instance_state(object)
    return state.has_identity

def _is_mapped_class(cls):
    """Return True if the given object is a mapped class, 
    :class:`.Mapper`, or :class:`.AliasedClass`."""

    if isinstance(cls, (AliasedClass, mapperlib.Mapper)):
        return True
    if isinstance(cls, expression.ClauseElement):
        return False
    if isinstance(cls, type):
        manager = attributes.manager_of_class(cls)
        return manager and _INSTRUMENTOR in manager.info
    return False

def _mapper_or_none(cls):
    """Return the :class:`.Mapper` for the given class or None if the 
    class is not mapped."""

    manager = attributes.manager_of_class(cls)
    if manager is not None and _INSTRUMENTOR in manager.info:
        return manager.info[_INSTRUMENTOR]
    else:
        return None

def instance_str(instance):
    """Return a string describing an instance."""

    return state_str(attributes.instance_state(instance))

def state_str(state):
    """Return a string describing an instance via its InstanceState."""

    if state is None:
        return "None"
    else:
        return '<%s at 0x%x>' % (state.class_.__name__, id(state.obj()))

def state_class_str(state):
    """Return a string describing an instance's class via its InstanceState."""

    if state is None:
        return "None"
    else:
        return '<%s>' % (state.class_.__name__, )

def attribute_str(instance, attribute):
    return instance_str(instance) + "." + attribute

def state_attribute_str(state, attribute):
    return state_str(state) + "." + attribute

def identity_equal(a, b):
    if a is b:
        return True
    if a is None or b is None:
        return False
    try:
        state_a = attributes.instance_state(a)
        state_b = attributes.instance_state(b)
    except exc.NO_STATE:
        return False
    if state_a.key is None or state_b.key is None:
        return False
    return state_a.key == state_b.key