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Ruud
2012-02-11 16:28:06 +01:00
parent 3bbf1126c3
commit 02e01fb2d6
217 changed files with 26395 additions and 21194 deletions
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libs/sqlalchemy/orm/interfaces.py
+216 -527
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@@ -1,26 +1,30 @@
# orm/interfaces.py
# Copyright (C) 2005-2011 the SQLAlchemy authors and contributors <see AUTHORS file>
# 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
"""
Semi-private module containing various base classes used throughout the ORM.
Contains various base classes used throughout the ORM.
Defines the extension classes :class:`MapperExtension`,
:class:`SessionExtension`, and :class:`AttributeExtension` as
well as other user-subclassable extension objects.
Defines the now deprecated ORM extension classes as well
as ORM internals.
Other than the deprecated extensions, this module and the
classes within should be considered mostly private.
"""
from itertools import chain
import sqlalchemy.exceptions as sa_exc
from sqlalchemy import log, util
from sqlalchemy.sql import expression
from sqlalchemy import exc as sa_exc
from sqlalchemy import util
from sqlalchemy.sql import operators
deque = __import__('collections').deque
mapperutil = util.importlater('sqlalchemy.orm', 'util')
class_mapper = None
collections = None
__all__ = (
@@ -48,373 +52,22 @@ ONETOMANY = util.symbol('ONETOMANY')
MANYTOONE = util.symbol('MANYTOONE')
MANYTOMANY = util.symbol('MANYTOMANY')
class MapperExtension(object):
"""Base implementation for customizing ``Mapper`` behavior.
from deprecated_interfaces import AttributeExtension, SessionExtension, \
MapperExtension
New extension classes subclass ``MapperExtension`` and are specified
using the ``extension`` mapper() argument, which is a single
``MapperExtension`` or a list of such. A single mapper
can maintain a chain of ``MapperExtension`` objects. When a
particular mapping event occurs, the corresponding method
on each ``MapperExtension`` is invoked serially, and each method
has the ability to halt the chain from proceeding further.
Each ``MapperExtension`` method returns the symbol
EXT_CONTINUE by default. This symbol generally means "move
to the next ``MapperExtension`` for processing". For methods
that return objects like translated rows or new object
instances, EXT_CONTINUE means the result of the method
should be ignored. In some cases it's required for a
default mapper activity to be performed, such as adding a
new instance to a result list.
The symbol EXT_STOP has significance within a chain
of ``MapperExtension`` objects that the chain will be stopped
when this symbol is returned. Like EXT_CONTINUE, it also
has additional significance in some cases that a default
mapper activity will not be performed.
"""
def instrument_class(self, mapper, class_):
"""Receive a class when the mapper is first constructed, and has
applied instrumentation to the mapped class.
The return value is only significant within the ``MapperExtension``
chain; the parent mapper's behavior isn't modified by this method.
"""
return EXT_CONTINUE
def init_instance(self, mapper, class_, oldinit, instance, args, kwargs):
"""Receive an instance when it's constructor is called.
This method is only called during a userland construction of
an object. It is not called when an object is loaded from the
database.
The return value is only significant within the ``MapperExtension``
chain; the parent mapper's behavior isn't modified by this method.
"""
return EXT_CONTINUE
def init_failed(self, mapper, class_, oldinit, instance, args, kwargs):
"""Receive an instance when it's constructor has been called,
and raised an exception.
This method is only called during a userland construction of
an object. It is not called when an object is loaded from the
database.
The return value is only significant within the ``MapperExtension``
chain; the parent mapper's behavior isn't modified by this method.
"""
return EXT_CONTINUE
def translate_row(self, mapper, context, row):
"""Perform pre-processing on the given result row and return a
new row instance.
This is called when the mapper first receives a row, before
the object identity or the instance itself has been derived
from that row. The given row may or may not be a
``RowProxy`` object - it will always be a dictionary-like
object which contains mapped columns as keys. The
returned object should also be a dictionary-like object
which recognizes mapped columns as keys.
If the ultimate return value is EXT_CONTINUE, the row
is not translated.
"""
return EXT_CONTINUE
def create_instance(self, mapper, selectcontext, row, class_):
"""Receive a row when a new object instance is about to be
created from that row.
The method can choose to create the instance itself, or it can return
EXT_CONTINUE to indicate normal object creation should take place.
mapper
The mapper doing the operation
selectcontext
The QueryContext generated from the Query.
row
The result row from the database
class\_
The class we are mapping.
return value
A new object instance, or EXT_CONTINUE
"""
return EXT_CONTINUE
def append_result(self, mapper, selectcontext, row, instance,
result, **flags):
"""Receive an object instance before that instance is appended
to a result list.
If this method returns EXT_CONTINUE, result appending will proceed
normally. if this method returns any other value or None,
result appending will not proceed for this instance, giving
this extension an opportunity to do the appending itself, if
desired.
mapper
The mapper doing the operation.
selectcontext
The QueryContext generated from the Query.
row
The result row from the database.
instance
The object instance to be appended to the result.
result
List to which results are being appended.
\**flags
extra information about the row, same as criterion in
``create_row_processor()`` method of
:class:`~sqlalchemy.orm.interfaces.MapperProperty`
"""
return EXT_CONTINUE
def populate_instance(self, mapper, selectcontext, row,
instance, **flags):
"""Receive an instance before that instance has
its attributes populated.
This usually corresponds to a newly loaded instance but may
also correspond to an already-loaded instance which has
unloaded attributes to be populated. The method may be called
many times for a single instance, as multiple result rows are
used to populate eagerly loaded collections.
If this method returns EXT_CONTINUE, instance population will
proceed normally. If any other value or None is returned,
instance population will not proceed, giving this extension an
opportunity to populate the instance itself, if desired.
As of 0.5, most usages of this hook are obsolete. For a
generic "object has been newly created from a row" hook, use
``reconstruct_instance()``, or the ``@orm.reconstructor``
decorator.
"""
return EXT_CONTINUE
def reconstruct_instance(self, mapper, instance):
"""Receive an object instance after it has been created via
``__new__``, and after initial attribute population has
occurred.
This typically occurs when the instance is created based on
incoming result rows, and is only called once for that
instance's lifetime.
Note that during a result-row load, this method is called upon
the first row received for this instance. Note that some
attributes and collections may or may not be loaded or even
initialized, depending on what's present in the result rows.
The return value is only significant within the ``MapperExtension``
chain; the parent mapper's behavior isn't modified by this method.
"""
return EXT_CONTINUE
def before_insert(self, mapper, connection, instance):
"""Receive an object instance before that instance is inserted
into its table.
This is a good place to set up primary key values and such
that aren't handled otherwise.
Column-based attributes can be modified within this method
which will result in the new value being inserted. However
*no* changes to the overall flush plan can be made, and
manipulation of the ``Session`` will not have the desired effect.
To manipulate the ``Session`` within an extension, use
``SessionExtension``.
The return value is only significant within the ``MapperExtension``
chain; the parent mapper's behavior isn't modified by this method.
"""
return EXT_CONTINUE
def after_insert(self, mapper, connection, instance):
"""Receive an object instance after that instance is inserted.
The return value is only significant within the ``MapperExtension``
chain; the parent mapper's behavior isn't modified by this method.
"""
return EXT_CONTINUE
def before_update(self, mapper, connection, instance):
"""Receive an object instance before that instance is updated.
Note that this method is called for all instances that are marked as
"dirty", even those which have no net changes to their column-based
attributes. An object is marked as dirty when any of its column-based
attributes have a "set attribute" operation called or when any of its
collections are modified. If, at update time, no column-based
attributes have any net changes, no UPDATE statement will be issued.
This means that an instance being sent to before_update is *not* a
guarantee that an UPDATE statement will be issued (although you can
affect the outcome here).
To detect if the column-based attributes on the object have net
changes, and will therefore generate an UPDATE statement, use
``object_session(instance).is_modified(instance,
include_collections=False)``.
Column-based attributes can be modified within this method
which will result in the new value being updated. However
*no* changes to the overall flush plan can be made, and
manipulation of the ``Session`` will not have the desired effect.
To manipulate the ``Session`` within an extension, use
``SessionExtension``.
The return value is only significant within the ``MapperExtension``
chain; the parent mapper's behavior isn't modified by this method.
"""
return EXT_CONTINUE
def after_update(self, mapper, connection, instance):
"""Receive an object instance after that instance is updated.
The return value is only significant within the ``MapperExtension``
chain; the parent mapper's behavior isn't modified by this method.
"""
return EXT_CONTINUE
def before_delete(self, mapper, connection, instance):
"""Receive an object instance before that instance is deleted.
Note that *no* changes to the overall flush plan can be made
here; and manipulation of the ``Session`` will not have the
desired effect. To manipulate the ``Session`` within an
extension, use ``SessionExtension``.
The return value is only significant within the ``MapperExtension``
chain; the parent mapper's behavior isn't modified by this method.
"""
return EXT_CONTINUE
def after_delete(self, mapper, connection, instance):
"""Receive an object instance after that instance is deleted.
The return value is only significant within the ``MapperExtension``
chain; the parent mapper's behavior isn't modified by this method.
"""
return EXT_CONTINUE
class SessionExtension(object):
"""An extension hook object for Sessions. Subclasses may be
installed into a Session (or sessionmaker) using the ``extension``
keyword argument. """
def before_commit(self, session):
"""Execute right before commit is called.
Note that this may not be per-flush if a longer running
transaction is ongoing."""
def after_commit(self, session):
"""Execute after a commit has occured.
Note that this may not be per-flush if a longer running
transaction is ongoing."""
def after_rollback(self, session):
"""Execute after a rollback has occured.
Note that this may not be per-flush if a longer running
transaction is ongoing."""
def before_flush( self, session, flush_context, instances):
"""Execute before flush process has started.
`instances` is an optional list of objects which were passed to
the ``flush()`` method. """
def after_flush(self, session, flush_context):
"""Execute after flush has completed, but before commit has been
called.
Note that the session's state is still in pre-flush, i.e. 'new',
'dirty', and 'deleted' lists still show pre-flush state as well
as the history settings on instance attributes."""
def after_flush_postexec(self, session, flush_context):
"""Execute after flush has completed, and after the post-exec
state occurs.
This will be when the 'new', 'dirty', and 'deleted' lists are in
their final state. An actual commit() may or may not have
occured, depending on whether or not the flush started its own
transaction or participated in a larger transaction. """
def after_begin( self, session, transaction, connection):
"""Execute after a transaction is begun on a connection
`transaction` is the SessionTransaction. This method is called
after an engine level transaction is begun on a connection. """
def after_attach(self, session, instance):
"""Execute after an instance is attached to a session.
This is called after an add, delete or merge. """
def after_bulk_update( self, session, query, query_context, result):
"""Execute after a bulk update operation to the session.
This is called after a session.query(...).update()
`query` is the query object that this update operation was
called on. `query_context` was the query context object.
`result` is the result object returned from the bulk operation.
"""
def after_bulk_delete( self, session, query, query_context, result):
"""Execute after a bulk delete operation to the session.
This is called after a session.query(...).delete()
`query` is the query object that this delete operation was
called on. `query_context` was the query context object.
`result` is the result object returned from the bulk operation.
"""
class MapperProperty(object):
"""Manage the relationship of a ``Mapper`` to a single class
attribute, as well as that attribute as it appears on individual
instances of the class, including attribute instrumentation,
attribute access, loading behavior, and dependency calculations.
The most common occurrences of :class:`.MapperProperty` are the
mapped :class:`.Column`, which is represented in a mapping as
an instance of :class:`.ColumnProperty`,
and a reference to another class produced by :func:`.relationship`,
represented in the mapping as an instance of :class:`.RelationshipProperty`.
"""
cascade = ()
@@ -424,7 +77,7 @@ class MapperProperty(object):
"""
def setup(self, context, entity, path, adapter, **kwargs):
def setup(self, context, entity, path, reduced_path, adapter, **kwargs):
"""Called by Query for the purposes of constructing a SQL statement.
Each MapperProperty associated with the target mapper processes the
@@ -434,12 +87,12 @@ class MapperProperty(object):
pass
def create_row_processor(self, selectcontext, path, mapper, row, adapter):
def create_row_processor(self, context, path, reduced_path,
mapper, row, adapter):
"""Return a 3-tuple consisting of three row processing functions.
"""
raise NotImplementedError()
return None, None, None
def cascade_iterator(self, type_, state, visited_instances=None,
halt_on=None):
@@ -519,9 +172,9 @@ class MapperProperty(object):
"""Merge the attribute represented by this ``MapperProperty``
from source to destination object"""
raise NotImplementedError()
pass
def compare(self, operator, value):
def compare(self, operator, value, **kw):
"""Return a compare operation for the columns represented by
this ``MapperProperty`` to the given value, which may be a
column value or an instance. 'operator' is an operator from
@@ -533,13 +186,13 @@ class MapperProperty(object):
return operator(self.comparator, value)
class PropComparator(expression.ColumnOperators):
class PropComparator(operators.ColumnOperators):
"""Defines comparison operations for MapperProperty objects.
User-defined subclasses of :class:`.PropComparator` may be created. The
built-in Python comparison and math operator methods, such as
``__eq__()``, ``__lt__()``, ``__add__()``, can be overridden to provide
new operator behaivor. The custom :class:`.PropComparator` is passed to
new operator behavior. The custom :class:`.PropComparator` is passed to
the mapper property via the ``comparator_factory`` argument. In each case,
the appropriate subclass of :class:`.PropComparator` should be used::
@@ -598,8 +251,7 @@ class PropComparator(expression.ColumnOperators):
query.join(Company.employees.of_type(Engineer)).\\
filter(Engineer.name=='foo')
\class_
a class or mapper indicating that criterion will be against
:param \class_: a class or mapper indicating that criterion will be against
this specific subclass.
@@ -611,13 +263,16 @@ class PropComparator(expression.ColumnOperators):
"""Return true if this collection contains any member that meets the
given criterion.
criterion
an optional ClauseElement formulated against the member class' table
or attributes.
The usual implementation of ``any()`` is
:meth:`.RelationshipProperty.Comparator.any`.
:param criterion: an optional ClauseElement formulated against the
member class' table or attributes.
:param \**kwargs: key/value pairs corresponding to member class attribute
names which will be compared via equality to the corresponding
values.
\**kwargs
key/value pairs corresponding to member class attribute names which
will be compared via equality to the corresponding values.
"""
return self.operate(PropComparator.any_op, criterion, **kwargs)
@@ -626,13 +281,16 @@ class PropComparator(expression.ColumnOperators):
"""Return true if this element references a member which meets the
given criterion.
criterion
an optional ClauseElement formulated against the member class' table
or attributes.
The usual implementation of ``has()`` is
:meth:`.RelationshipProperty.Comparator.has`.
:param criterion: an optional ClauseElement formulated against the
member class' table or attributes.
:param \**kwargs: key/value pairs corresponding to member class attribute
names which will be compared via equality to the corresponding
values.
\**kwargs
key/value pairs corresponding to member class attribute names which
will be compared via equality to the corresponding values.
"""
return self.operate(PropComparator.has_op, criterion, **kwargs)
@@ -648,38 +306,47 @@ class StrategizedProperty(MapperProperty):
"""
def _get_context_strategy(self, context, path):
cls = context.attributes.get(('loaderstrategy',
_reduce_path(path)), None)
strategy_wildcard_key = None
def _get_context_strategy(self, context, reduced_path):
key = ('loaderstrategy', reduced_path)
cls = None
if key in context.attributes:
cls = context.attributes[key]
elif self.strategy_wildcard_key:
key = ('loaderstrategy', (self.strategy_wildcard_key,))
if key in context.attributes:
cls = context.attributes[key]
if cls:
try:
return self.__all_strategies[cls]
return self._strategies[cls]
except KeyError:
return self.__init_strategy(cls)
else:
return self.strategy
return self.strategy
def _get_strategy(self, cls):
try:
return self.__all_strategies[cls]
return self._strategies[cls]
except KeyError:
return self.__init_strategy(cls)
def __init_strategy(self, cls):
self.__all_strategies[cls] = strategy = cls(self)
strategy.init()
self._strategies[cls] = strategy = cls(self)
return strategy
def setup(self, context, entity, path, adapter, **kwargs):
self._get_context_strategy(context, path + (self.key,)).\
setup_query(context, entity, path, adapter, **kwargs)
def setup(self, context, entity, path, reduced_path, adapter, **kwargs):
self._get_context_strategy(context, reduced_path + (self.key,)).\
setup_query(context, entity, path,
reduced_path, adapter, **kwargs)
def create_row_processor(self, context, path, mapper, row, adapter):
return self._get_context_strategy(context, path + (self.key,)).\
create_row_processor(context, path, mapper, row, adapter)
def create_row_processor(self, context, path, reduced_path, mapper, row, adapter):
return self._get_context_strategy(context, reduced_path + (self.key,)).\
create_row_processor(context, path,
reduced_path, mapper, row, adapter)
def do_init(self):
self.__all_strategies = {}
self._strategies = {}
self.strategy = self.__init_strategy(self.strategy_class)
def post_instrument_class(self, mapper):
@@ -706,11 +373,7 @@ def deserialize_path(path):
if path is None:
return None
global class_mapper
if class_mapper is None:
from sqlalchemy.orm import class_mapper
p = tuple(chain(*[(class_mapper(cls), key) for cls, key in path]))
p = tuple(chain(*[(mapperutil.class_mapper(cls), key) for cls, key in path]))
if p and p[-1] is None:
p = p[0:-1]
return p
@@ -735,22 +398,10 @@ class MapperOption(object):
self.process_query(query)
class ExtensionOption(MapperOption):
"""a MapperOption that applies a MapperExtension to a query
operation."""
def __init__(self, ext):
self.ext = ext
def process_query(self, query):
entity = query._generate_mapper_zero()
entity.extension = entity.extension.copy()
entity.extension.push(self.ext)
class PropertyOption(MapperOption):
"""A MapperOption that is applied to a property off the mapper or
one of its child mappers, identified by a dot-separated key. """
one of its child mappers, identified by a dot-separated key
or list of class-bound attributes. """
def __init__(self, key, mapper=None):
self.key = key
@@ -791,14 +442,12 @@ class PropertyOption(MapperOption):
state['key'] = tuple(ret)
self.__dict__ = state
def _find_entity( self, query, mapper, raiseerr):
from sqlalchemy.orm.util import _class_to_mapper, \
_is_aliased_class
if _is_aliased_class(mapper):
def _find_entity_prop_comparator(self, query, token, mapper, raiseerr):
if mapperutil._is_aliased_class(mapper):
searchfor = mapper
isa = False
else:
searchfor = _class_to_mapper(mapper)
searchfor = mapperutil._class_to_mapper(mapper)
isa = True
for ent in query._mapper_entities:
if searchfor is ent.path_entity or isa \
@@ -806,9 +455,36 @@ class PropertyOption(MapperOption):
return ent
else:
if raiseerr:
raise sa_exc.ArgumentError("Can't find entity %s in "
"Query. Current list: %r" % (searchfor,
[str(m.path_entity) for m in query._entities]))
if not list(query._mapper_entities):
raise sa_exc.ArgumentError(
"Query has only expression-based entities - "
"can't find property named '%s'."
% (token, )
)
else:
raise sa_exc.ArgumentError(
"Can't find property '%s' on any entity "
"specified in this Query. Note the full path "
"from root (%s) to target entity must be specified."
% (token, ",".join(str(x) for
x in query._mapper_entities))
)
else:
return None
def _find_entity_basestring(self, query, token, raiseerr):
for ent in query._mapper_entities:
# return only the first _MapperEntity when searching
# based on string prop name. Ideally object
# attributes are used to specify more exactly.
return ent
else:
if raiseerr:
raise sa_exc.ArgumentError(
"Query has only expression-based entities - "
"can't find property named '%s'."
% (token, )
)
else:
return None
@@ -818,114 +494,112 @@ class PropertyOption(MapperOption):
l = []
mappers = []
# _current_path implies we're in a secondary load with an
# existing path
# _current_path implies we're in a
# secondary load with an existing path
current_path = list(query._current_path)
tokens = []
for key in util.to_list(self.key):
if isinstance(key, basestring):
tokens += key.split('.')
else:
tokens += [key]
for token in tokens:
tokens = deque(self.key)
while tokens:
token = tokens.popleft()
if isinstance(token, basestring):
# wildcard token
if token.endswith(':*'):
return [(token,)], []
sub_tokens = token.split(".", 1)
token = sub_tokens[0]
tokens.extendleft(sub_tokens[1:])
# exhaust current_path before
# matching tokens to entities
if current_path:
if current_path[1] == token:
current_path = current_path[2:]
continue
else:
return [], []
if not entity:
if current_path:
if current_path[1] == token:
current_path = current_path[2:]
continue
entity = query._entity_zero()
entity = self._find_entity_basestring(
query,
token,
raiseerr)
if entity is None:
return [], []
path_element = entity.path_entity
mapper = entity.mapper
mappers.append(mapper)
prop = mapper.get_property(token,
resolve_synonyms=True, raiseerr=raiseerr)
key = token
if hasattr(mapper.class_, token):
prop = getattr(mapper.class_, token).property
else:
if raiseerr:
raise sa_exc.ArgumentError(
"Can't find property named '%s' on the "
"mapped entity %s in this Query. " % (
token, mapper)
)
else:
return [], []
elif isinstance(token, PropComparator):
prop = token.property
# exhaust current_path before
# matching tokens to entities
if current_path:
if current_path[0:2] == \
[token.parententity, prop.key]:
current_path = current_path[2:]
continue
else:
return [], []
if not entity:
if current_path:
if current_path[0:2] == [token.parententity,
prop.key]:
current_path = current_path[2:]
continue
entity = self._find_entity(query,
token.parententity, raiseerr)
entity = self._find_entity_prop_comparator(
query,
prop.key,
token.parententity,
raiseerr)
if not entity:
return [], []
path_element = entity.path_entity
mapper = entity.mapper
mappers.append(prop.parent)
key = prop.key
else:
raise sa_exc.ArgumentError('mapper option expects '
'string key or list of attributes')
if prop is None:
return [], []
raise sa_exc.ArgumentError(
"mapper option expects "
"string key or list of attributes")
assert prop is not None
if raiseerr and not prop.parent.common_parent(mapper):
raise sa_exc.ArgumentError("Attribute '%s' does not "
"link from element '%s'" % (token, path_element))
path = build_path(path_element, prop.key, path)
l.append(path)
if getattr(token, '_of_type', None):
path_element = mapper = token._of_type
else:
path_element = mapper = getattr(prop, 'mapper', None)
if path_element:
path_element = path_element
if mapper is None and tokens:
raise sa_exc.ArgumentError(
"Attribute '%s' of entity '%s' does not "
"refer to a mapped entity" %
(token, entity)
)
if current_path:
# ran out of tokens before
# current_path was exhausted.
assert not tokens
return [], []
return l, mappers
class AttributeExtension(object):
"""An event handler for individual attribute change events.
AttributeExtension is assembled within the descriptors associated
with a mapped class.
"""
active_history = True
"""indicates that the set() method would like to receive the 'old' value,
even if it means firing lazy callables.
Note that ``active_history`` can also be set directly via
:func:`.column_property` and :func:`.relationship`.
"""
def append(self, state, value, initiator):
"""Receive a collection append event.
The returned value will be used as the actual value to be
appended.
"""
return value
def remove(self, state, value, initiator):
"""Receive a remove event.
No return value is defined.
"""
pass
def set(self, state, value, oldvalue, initiator):
"""Receive a set event.
The returned value will be used as the actual value to be
set.
"""
return value
class StrategizedOption(PropertyOption):
"""A MapperOption that affects which LoaderStrategy will be used
for an operation by a StrategizedProperty.
"""
is_chained = False
chained = False
def process_query_property(self, query, paths, mappers):
@@ -935,7 +609,7 @@ class StrategizedOption(PropertyOption):
# "(Person, 'machines')" in the path due to the mechanics of how
# the eager strategy builds up the path
if self.is_chained:
if self.chained:
for path in paths:
query._attributes[('loaderstrategy',
_reduce_path(path))] = \
@@ -953,13 +627,13 @@ def _reduce_path(path):
This is used to allow more open ended selection of loader strategies, i.e.
Mapper -> prop1 -> Subclass -> prop2, where Subclass is a sub-mapper
of the mapper referened by Mapper.prop1.
of the mapper referenced by Mapper.prop1.
"""
return tuple([i % 2 != 0 and
path[i] or
getattr(path[i], 'base_mapper', path[i])
for i in xrange(len(path))])
element or
getattr(element, 'base_mapper', element)
for i, element in enumerate(path)])
class LoaderStrategy(object):
"""Describe the loading behavior of a StrategizedProperty object.
@@ -975,22 +649,25 @@ class LoaderStrategy(object):
* it processes the ``QueryContext`` at statement construction time,
where it can modify the SQL statement that is being produced.
simple column attributes may add their represented column to the
Simple column attributes may add their represented column to the
list of selected columns, *eager loading* properties may add
``LEFT OUTER JOIN`` clauses to the statement.
* it processes the ``SelectionContext`` at row-processing time. This
includes straight population of attributes corresponding to rows,
setting instance-level lazyloader callables on newly
constructed instances, and appending child items to scalar/collection
attributes in response to eagerly-loaded relations.
"""
* It produces "row processor" functions at result fetching time.
These "row processor" functions populate a particular attribute
on a particular mapped instance.
"""
def __init__(self, parent):
self.parent_property = parent
self.is_class_level = False
self.parent = self.parent_property.parent
self.key = self.parent_property.key
# TODO: there's no particular reason we need
# the separate .init() method at this point.
# It's possible someone has written their
# own LS object.
self.init()
def init(self):
raise NotImplementedError("LoaderStrategy")
@@ -998,10 +675,10 @@ class LoaderStrategy(object):
def init_class_attribute(self, mapper):
pass
def setup_query(self, context, entity, path, adapter, **kwargs):
def setup_query(self, context, entity, path, reduced_path, adapter, **kwargs):
pass
def create_row_processor(self, selectcontext, path, mapper,
def create_row_processor(self, context, path, reduced_path, mapper,
row, adapter):
"""Return row processing functions which fulfill the contract
specified by MapperProperty.create_row_processor.
@@ -1009,7 +686,7 @@ class LoaderStrategy(object):
StrategizedProperty delegates its create_row_processor method
directly to this method. """
raise NotImplementedError()
return None, None, None
def __str__(self):
return str(self.parent_property)
@@ -1028,6 +705,18 @@ class LoaderStrategy(object):
class InstrumentationManager(object):
"""User-defined class instrumentation extension.
:class:`.InstrumentationManager` can be subclassed in order
to change
how class instrumentation proceeds. This class exists for
the purposes of integration with other object management
frameworks which would like to entirely modify the
instrumentation methodology of the ORM, and is not intended
for regular usage. For interception of class instrumentation
events, see :class:`.InstrumentationEvents`.
For an example of :class:`.InstrumentationManager`, see the
example :ref:`examples_instrumentation`.
The API for this class should be considered as semi-stable,
and may change slightly with new releases.
@@ -1085,7 +774,7 @@ class InstrumentationManager(object):
setattr(instance, '_default_state', state)
def remove_state(self, class_, instance):
delattr(instance, '_default_state', state)
delattr(instance, '_default_state')
def state_getter(self, class_):
return lambda instance: getattr(instance, '_default_state')