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1094 lines
36 KiB
1094 lines
36 KiB
# orm/interfaces.py
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# Copyright (C) 2005-2011 the SQLAlchemy authors and contributors <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""
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Semi-private module containing various base classes used throughout the ORM.
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Defines the extension classes :class:`MapperExtension`,
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:class:`SessionExtension`, and :class:`AttributeExtension` as
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well as other user-subclassable extension objects.
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"""
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from itertools import chain
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import sqlalchemy.exceptions as sa_exc
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from sqlalchemy import log, util
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from sqlalchemy.sql import expression
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class_mapper = None
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collections = None
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__all__ = (
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'AttributeExtension',
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'EXT_CONTINUE',
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'EXT_STOP',
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'ExtensionOption',
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'InstrumentationManager',
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'LoaderStrategy',
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'MapperExtension',
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'MapperOption',
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'MapperProperty',
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'PropComparator',
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'PropertyOption',
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'SessionExtension',
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'StrategizedOption',
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'StrategizedProperty',
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'build_path',
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)
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EXT_CONTINUE = util.symbol('EXT_CONTINUE')
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EXT_STOP = util.symbol('EXT_STOP')
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ONETOMANY = util.symbol('ONETOMANY')
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MANYTOONE = util.symbol('MANYTOONE')
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MANYTOMANY = util.symbol('MANYTOMANY')
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class MapperExtension(object):
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"""Base implementation for customizing ``Mapper`` behavior.
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New extension classes subclass ``MapperExtension`` and are specified
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using the ``extension`` mapper() argument, which is a single
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``MapperExtension`` or a list of such. A single mapper
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can maintain a chain of ``MapperExtension`` objects. When a
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particular mapping event occurs, the corresponding method
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on each ``MapperExtension`` is invoked serially, and each method
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has the ability to halt the chain from proceeding further.
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Each ``MapperExtension`` method returns the symbol
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EXT_CONTINUE by default. This symbol generally means "move
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to the next ``MapperExtension`` for processing". For methods
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that return objects like translated rows or new object
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instances, EXT_CONTINUE means the result of the method
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should be ignored. In some cases it's required for a
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default mapper activity to be performed, such as adding a
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new instance to a result list.
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The symbol EXT_STOP has significance within a chain
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of ``MapperExtension`` objects that the chain will be stopped
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when this symbol is returned. Like EXT_CONTINUE, it also
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has additional significance in some cases that a default
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mapper activity will not be performed.
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"""
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def instrument_class(self, mapper, class_):
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"""Receive a class when the mapper is first constructed, and has
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applied instrumentation to the mapped class.
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The return value is only significant within the ``MapperExtension``
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chain; the parent mapper's behavior isn't modified by this method.
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"""
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return EXT_CONTINUE
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def init_instance(self, mapper, class_, oldinit, instance, args, kwargs):
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"""Receive an instance when it's constructor is called.
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This method is only called during a userland construction of
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an object. It is not called when an object is loaded from the
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database.
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The return value is only significant within the ``MapperExtension``
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chain; the parent mapper's behavior isn't modified by this method.
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"""
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return EXT_CONTINUE
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def init_failed(self, mapper, class_, oldinit, instance, args, kwargs):
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"""Receive an instance when it's constructor has been called,
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and raised an exception.
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This method is only called during a userland construction of
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an object. It is not called when an object is loaded from the
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database.
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The return value is only significant within the ``MapperExtension``
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chain; the parent mapper's behavior isn't modified by this method.
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"""
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return EXT_CONTINUE
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def translate_row(self, mapper, context, row):
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"""Perform pre-processing on the given result row and return a
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new row instance.
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This is called when the mapper first receives a row, before
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the object identity or the instance itself has been derived
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from that row. The given row may or may not be a
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``RowProxy`` object - it will always be a dictionary-like
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object which contains mapped columns as keys. The
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returned object should also be a dictionary-like object
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which recognizes mapped columns as keys.
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If the ultimate return value is EXT_CONTINUE, the row
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is not translated.
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"""
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return EXT_CONTINUE
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def create_instance(self, mapper, selectcontext, row, class_):
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"""Receive a row when a new object instance is about to be
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created from that row.
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The method can choose to create the instance itself, or it can return
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EXT_CONTINUE to indicate normal object creation should take place.
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mapper
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The mapper doing the operation
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selectcontext
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The QueryContext generated from the Query.
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row
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The result row from the database
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class\_
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The class we are mapping.
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return value
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A new object instance, or EXT_CONTINUE
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"""
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return EXT_CONTINUE
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def append_result(self, mapper, selectcontext, row, instance,
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result, **flags):
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"""Receive an object instance before that instance is appended
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to a result list.
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If this method returns EXT_CONTINUE, result appending will proceed
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normally. if this method returns any other value or None,
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result appending will not proceed for this instance, giving
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this extension an opportunity to do the appending itself, if
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desired.
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mapper
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The mapper doing the operation.
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selectcontext
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The QueryContext generated from the Query.
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row
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The result row from the database.
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instance
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The object instance to be appended to the result.
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result
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List to which results are being appended.
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\**flags
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extra information about the row, same as criterion in
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``create_row_processor()`` method of
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:class:`~sqlalchemy.orm.interfaces.MapperProperty`
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"""
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return EXT_CONTINUE
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def populate_instance(self, mapper, selectcontext, row,
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instance, **flags):
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"""Receive an instance before that instance has
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its attributes populated.
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This usually corresponds to a newly loaded instance but may
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also correspond to an already-loaded instance which has
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unloaded attributes to be populated. The method may be called
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many times for a single instance, as multiple result rows are
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used to populate eagerly loaded collections.
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If this method returns EXT_CONTINUE, instance population will
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proceed normally. If any other value or None is returned,
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instance population will not proceed, giving this extension an
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opportunity to populate the instance itself, if desired.
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As of 0.5, most usages of this hook are obsolete. For a
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generic "object has been newly created from a row" hook, use
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``reconstruct_instance()``, or the ``@orm.reconstructor``
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decorator.
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"""
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return EXT_CONTINUE
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def reconstruct_instance(self, mapper, instance):
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"""Receive an object instance after it has been created via
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``__new__``, and after initial attribute population has
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occurred.
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This typically occurs when the instance is created based on
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incoming result rows, and is only called once for that
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instance's lifetime.
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Note that during a result-row load, this method is called upon
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the first row received for this instance. Note that some
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attributes and collections may or may not be loaded or even
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initialized, depending on what's present in the result rows.
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The return value is only significant within the ``MapperExtension``
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chain; the parent mapper's behavior isn't modified by this method.
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"""
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return EXT_CONTINUE
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def before_insert(self, mapper, connection, instance):
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"""Receive an object instance before that instance is inserted
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into its table.
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This is a good place to set up primary key values and such
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that aren't handled otherwise.
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Column-based attributes can be modified within this method
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which will result in the new value being inserted. However
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*no* changes to the overall flush plan can be made, and
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manipulation of the ``Session`` will not have the desired effect.
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To manipulate the ``Session`` within an extension, use
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``SessionExtension``.
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The return value is only significant within the ``MapperExtension``
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chain; the parent mapper's behavior isn't modified by this method.
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"""
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return EXT_CONTINUE
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def after_insert(self, mapper, connection, instance):
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"""Receive an object instance after that instance is inserted.
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The return value is only significant within the ``MapperExtension``
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chain; the parent mapper's behavior isn't modified by this method.
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"""
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return EXT_CONTINUE
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def before_update(self, mapper, connection, instance):
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"""Receive an object instance before that instance is updated.
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Note that this method is called for all instances that are marked as
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"dirty", even those which have no net changes to their column-based
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attributes. An object is marked as dirty when any of its column-based
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attributes have a "set attribute" operation called or when any of its
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collections are modified. If, at update time, no column-based
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attributes have any net changes, no UPDATE statement will be issued.
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This means that an instance being sent to before_update is *not* a
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guarantee that an UPDATE statement will be issued (although you can
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affect the outcome here).
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To detect if the column-based attributes on the object have net
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changes, and will therefore generate an UPDATE statement, use
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``object_session(instance).is_modified(instance,
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include_collections=False)``.
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Column-based attributes can be modified within this method
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which will result in the new value being updated. However
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*no* changes to the overall flush plan can be made, and
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manipulation of the ``Session`` will not have the desired effect.
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To manipulate the ``Session`` within an extension, use
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``SessionExtension``.
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The return value is only significant within the ``MapperExtension``
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chain; the parent mapper's behavior isn't modified by this method.
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"""
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return EXT_CONTINUE
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def after_update(self, mapper, connection, instance):
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"""Receive an object instance after that instance is updated.
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The return value is only significant within the ``MapperExtension``
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chain; the parent mapper's behavior isn't modified by this method.
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"""
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return EXT_CONTINUE
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def before_delete(self, mapper, connection, instance):
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"""Receive an object instance before that instance is deleted.
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Note that *no* changes to the overall flush plan can be made
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here; and manipulation of the ``Session`` will not have the
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desired effect. To manipulate the ``Session`` within an
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extension, use ``SessionExtension``.
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The return value is only significant within the ``MapperExtension``
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chain; the parent mapper's behavior isn't modified by this method.
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"""
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return EXT_CONTINUE
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def after_delete(self, mapper, connection, instance):
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"""Receive an object instance after that instance is deleted.
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The return value is only significant within the ``MapperExtension``
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chain; the parent mapper's behavior isn't modified by this method.
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"""
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return EXT_CONTINUE
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class SessionExtension(object):
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"""An extension hook object for Sessions. Subclasses may be
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installed into a Session (or sessionmaker) using the ``extension``
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keyword argument. """
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def before_commit(self, session):
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"""Execute right before commit is called.
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Note that this may not be per-flush if a longer running
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transaction is ongoing."""
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def after_commit(self, session):
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"""Execute after a commit has occured.
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Note that this may not be per-flush if a longer running
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transaction is ongoing."""
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def after_rollback(self, session):
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"""Execute after a rollback has occured.
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Note that this may not be per-flush if a longer running
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transaction is ongoing."""
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def before_flush( self, session, flush_context, instances):
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"""Execute before flush process has started.
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`instances` is an optional list of objects which were passed to
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the ``flush()`` method. """
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def after_flush(self, session, flush_context):
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"""Execute after flush has completed, but before commit has been
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called.
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Note that the session's state is still in pre-flush, i.e. 'new',
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'dirty', and 'deleted' lists still show pre-flush state as well
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as the history settings on instance attributes."""
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def after_flush_postexec(self, session, flush_context):
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"""Execute after flush has completed, and after the post-exec
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state occurs.
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This will be when the 'new', 'dirty', and 'deleted' lists are in
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their final state. An actual commit() may or may not have
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occured, depending on whether or not the flush started its own
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transaction or participated in a larger transaction. """
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def after_begin( self, session, transaction, connection):
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"""Execute after a transaction is begun on a connection
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`transaction` is the SessionTransaction. This method is called
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after an engine level transaction is begun on a connection. """
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def after_attach(self, session, instance):
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"""Execute after an instance is attached to a session.
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This is called after an add, delete or merge. """
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def after_bulk_update( self, session, query, query_context, result):
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"""Execute after a bulk update operation to the session.
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This is called after a session.query(...).update()
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`query` is the query object that this update operation was
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called on. `query_context` was the query context object.
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`result` is the result object returned from the bulk operation.
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"""
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def after_bulk_delete( self, session, query, query_context, result):
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"""Execute after a bulk delete operation to the session.
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This is called after a session.query(...).delete()
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`query` is the query object that this delete operation was
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called on. `query_context` was the query context object.
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`result` is the result object returned from the bulk operation.
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"""
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class MapperProperty(object):
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"""Manage the relationship of a ``Mapper`` to a single class
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attribute, as well as that attribute as it appears on individual
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instances of the class, including attribute instrumentation,
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attribute access, loading behavior, and dependency calculations.
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"""
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cascade = ()
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"""The set of 'cascade' attribute names.
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This collection is checked before the 'cascade_iterator' method is called.
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"""
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def setup(self, context, entity, path, adapter, **kwargs):
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"""Called by Query for the purposes of constructing a SQL statement.
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Each MapperProperty associated with the target mapper processes the
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statement referenced by the query context, adding columns and/or
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criterion as appropriate.
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"""
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pass
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def create_row_processor(self, selectcontext, path, mapper, row, adapter):
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"""Return a 3-tuple consisting of three row processing functions.
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"""
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raise NotImplementedError()
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def cascade_iterator(self, type_, state, visited_instances=None,
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halt_on=None):
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"""Iterate through instances related to the given instance for
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a particular 'cascade', starting with this MapperProperty.
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Return an iterator3-tuples (instance, mapper, state).
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Note that the 'cascade' collection on this MapperProperty is
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checked first for the given type before cascade_iterator is called.
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See PropertyLoader for the related instance implementation.
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"""
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return iter(())
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def set_parent(self, parent, init):
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self.parent = parent
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def instrument_class(self, mapper):
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raise NotImplementedError()
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_compile_started = False
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_compile_finished = False
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def init(self):
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"""Called after all mappers are created to assemble
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relationships between mappers and perform other post-mapper-creation
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initialization steps.
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"""
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self._compile_started = True
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self.do_init()
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self._compile_finished = True
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@property
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def class_attribute(self):
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"""Return the class-bound descriptor corresponding to this
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MapperProperty."""
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return getattr(self.parent.class_, self.key)
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def do_init(self):
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"""Perform subclass-specific initialization post-mapper-creation
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steps.
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This is a template method called by the ``MapperProperty``
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object's init() method.
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"""
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pass
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def post_instrument_class(self, mapper):
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"""Perform instrumentation adjustments that need to occur
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after init() has completed.
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"""
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pass
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def per_property_preprocessors(self, uow):
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pass
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def is_primary(self):
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"""Return True if this ``MapperProperty``'s mapper is the
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primary mapper for its class.
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This flag is used to indicate that the ``MapperProperty`` can
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define attribute instrumentation for the class at the class
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level (as opposed to the individual instance level).
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"""
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return not self.parent.non_primary
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def merge(self, session, source_state, source_dict, dest_state,
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dest_dict, load, _recursive):
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"""Merge the attribute represented by this ``MapperProperty``
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from source to destination object"""
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raise NotImplementedError()
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def compare(self, operator, value):
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"""Return a compare operation for the columns represented by
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this ``MapperProperty`` to the given value, which may be a
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column value or an instance. 'operator' is an operator from
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the operators module, or from sql.Comparator.
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By default uses the PropComparator attached to this MapperProperty
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under the attribute name "comparator".
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"""
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return operator(self.comparator, value)
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class PropComparator(expression.ColumnOperators):
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"""Defines comparison operations for MapperProperty objects.
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User-defined subclasses of :class:`.PropComparator` may be created. The
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built-in Python comparison and math operator methods, such as
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``__eq__()``, ``__lt__()``, ``__add__()``, can be overridden to provide
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new operator behaivor. The custom :class:`.PropComparator` is passed to
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the mapper property via the ``comparator_factory`` argument. In each case,
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the appropriate subclass of :class:`.PropComparator` should be used::
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from sqlalchemy.orm.properties import \\
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ColumnProperty,\\
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CompositeProperty,\\
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RelationshipProperty
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class MyColumnComparator(ColumnProperty.Comparator):
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pass
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class MyCompositeComparator(CompositeProperty.Comparator):
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pass
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class MyRelationshipComparator(RelationshipProperty.Comparator):
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pass
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"""
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def __init__(self, prop, mapper, adapter=None):
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self.prop = self.property = prop
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self.mapper = mapper
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self.adapter = adapter
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def __clause_element__(self):
|
|
raise NotImplementedError("%r" % self)
|
|
|
|
def adapted(self, adapter):
|
|
"""Return a copy of this PropComparator which will use the given
|
|
adaption function on the local side of generated expressions.
|
|
|
|
"""
|
|
|
|
return self.__class__(self.prop, self.mapper, adapter)
|
|
|
|
@staticmethod
|
|
def any_op(a, b, **kwargs):
|
|
return a.any(b, **kwargs)
|
|
|
|
@staticmethod
|
|
def has_op(a, b, **kwargs):
|
|
return a.has(b, **kwargs)
|
|
|
|
@staticmethod
|
|
def of_type_op(a, class_):
|
|
return a.of_type(class_)
|
|
|
|
def of_type(self, class_):
|
|
"""Redefine this object in terms of a polymorphic subclass.
|
|
|
|
Returns a new PropComparator from which further criterion can be
|
|
evaluated.
|
|
|
|
e.g.::
|
|
|
|
query.join(Company.employees.of_type(Engineer)).\\
|
|
filter(Engineer.name=='foo')
|
|
|
|
\class_
|
|
a class or mapper indicating that criterion will be against
|
|
this specific subclass.
|
|
|
|
|
|
"""
|
|
|
|
return self.operate(PropComparator.of_type_op, class_)
|
|
|
|
def any(self, criterion=None, **kwargs):
|
|
"""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.
|
|
|
|
\**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)
|
|
|
|
def has(self, criterion=None, **kwargs):
|
|
"""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.
|
|
|
|
\**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)
|
|
|
|
|
|
class StrategizedProperty(MapperProperty):
|
|
"""A MapperProperty which uses selectable strategies to affect
|
|
loading behavior.
|
|
|
|
There is a single strategy selected by default. Alternate
|
|
strategies can be selected at Query time through the usage of
|
|
``StrategizedOption`` objects via the Query.options() method.
|
|
|
|
"""
|
|
|
|
def _get_context_strategy(self, context, path):
|
|
cls = context.attributes.get(('loaderstrategy',
|
|
_reduce_path(path)), None)
|
|
if cls:
|
|
try:
|
|
return self.__all_strategies[cls]
|
|
except KeyError:
|
|
return self.__init_strategy(cls)
|
|
else:
|
|
return self.strategy
|
|
|
|
def _get_strategy(self, cls):
|
|
try:
|
|
return self.__all_strategies[cls]
|
|
except KeyError:
|
|
return self.__init_strategy(cls)
|
|
|
|
def __init_strategy(self, cls):
|
|
self.__all_strategies[cls] = strategy = cls(self)
|
|
strategy.init()
|
|
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 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 do_init(self):
|
|
self.__all_strategies = {}
|
|
self.strategy = self.__init_strategy(self.strategy_class)
|
|
|
|
def post_instrument_class(self, mapper):
|
|
if self.is_primary() and \
|
|
not mapper.class_manager._attr_has_impl(self.key):
|
|
self.strategy.init_class_attribute(mapper)
|
|
|
|
def build_path(entity, key, prev=None):
|
|
if prev:
|
|
return prev + (entity, key)
|
|
else:
|
|
return (entity, key)
|
|
|
|
def serialize_path(path):
|
|
if path is None:
|
|
return None
|
|
|
|
return zip(
|
|
[m.class_ for m in [path[i] for i in range(0, len(path), 2)]],
|
|
[path[i] for i in range(1, len(path), 2)] + [None]
|
|
)
|
|
|
|
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]))
|
|
if p and p[-1] is None:
|
|
p = p[0:-1]
|
|
return p
|
|
|
|
class MapperOption(object):
|
|
"""Describe a modification to a Query."""
|
|
|
|
propagate_to_loaders = False
|
|
"""if True, indicate this option should be carried along
|
|
Query object generated by scalar or object lazy loaders.
|
|
"""
|
|
|
|
def process_query(self, query):
|
|
pass
|
|
|
|
def process_query_conditionally(self, query):
|
|
"""same as process_query(), except that this option may not
|
|
apply to the given query.
|
|
|
|
Used when secondary loaders resend existing options to a new
|
|
Query."""
|
|
|
|
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. """
|
|
|
|
def __init__(self, key, mapper=None):
|
|
self.key = key
|
|
self.mapper = mapper
|
|
|
|
def process_query(self, query):
|
|
self._process(query, True)
|
|
|
|
def process_query_conditionally(self, query):
|
|
self._process(query, False)
|
|
|
|
def _process(self, query, raiseerr):
|
|
paths, mappers = self._get_paths(query, raiseerr)
|
|
if paths:
|
|
self.process_query_property(query, paths, mappers)
|
|
|
|
def process_query_property(self, query, paths, mappers):
|
|
pass
|
|
|
|
def __getstate__(self):
|
|
d = self.__dict__.copy()
|
|
d['key'] = ret = []
|
|
for token in util.to_list(self.key):
|
|
if isinstance(token, PropComparator):
|
|
ret.append((token.mapper.class_, token.key))
|
|
else:
|
|
ret.append(token)
|
|
return d
|
|
|
|
def __setstate__(self, state):
|
|
ret = []
|
|
for key in state['key']:
|
|
if isinstance(key, tuple):
|
|
cls, propkey = key
|
|
ret.append(getattr(cls, propkey))
|
|
else:
|
|
ret.append(key)
|
|
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):
|
|
searchfor = mapper
|
|
isa = False
|
|
else:
|
|
searchfor = _class_to_mapper(mapper)
|
|
isa = True
|
|
for ent in query._mapper_entities:
|
|
if searchfor is ent.path_entity or isa \
|
|
and searchfor.common_parent(ent.path_entity):
|
|
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]))
|
|
else:
|
|
return None
|
|
|
|
def _get_paths(self, query, raiseerr):
|
|
path = None
|
|
entity = None
|
|
l = []
|
|
mappers = []
|
|
|
|
# _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:
|
|
if isinstance(token, basestring):
|
|
if not entity:
|
|
if current_path:
|
|
if current_path[1] == token:
|
|
current_path = current_path[2:]
|
|
continue
|
|
entity = query._entity_zero()
|
|
path_element = entity.path_entity
|
|
mapper = entity.mapper
|
|
mappers.append(mapper)
|
|
prop = mapper.get_property(token,
|
|
resolve_synonyms=True, raiseerr=raiseerr)
|
|
key = token
|
|
elif isinstance(token, PropComparator):
|
|
prop = token.property
|
|
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)
|
|
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 [], []
|
|
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 current_path:
|
|
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
|
|
|
|
def process_query_property(self, query, paths, mappers):
|
|
|
|
# _get_context_strategy may receive the path in terms of a base
|
|
# mapper - e.g. options(eagerload_all(Company.employees,
|
|
# Engineer.machines)) in the polymorphic tests leads to
|
|
# "(Person, 'machines')" in the path due to the mechanics of how
|
|
# the eager strategy builds up the path
|
|
|
|
if self.is_chained:
|
|
for path in paths:
|
|
query._attributes[('loaderstrategy',
|
|
_reduce_path(path))] = \
|
|
self.get_strategy_class()
|
|
else:
|
|
query._attributes[('loaderstrategy',
|
|
_reduce_path(paths[-1]))] = \
|
|
self.get_strategy_class()
|
|
|
|
def get_strategy_class(self):
|
|
raise NotImplementedError()
|
|
|
|
def _reduce_path(path):
|
|
"""Convert a (mapper, path) path to use base mappers.
|
|
|
|
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.
|
|
|
|
"""
|
|
return tuple([i % 2 != 0 and
|
|
path[i] or
|
|
getattr(path[i], 'base_mapper', path[i])
|
|
for i in xrange(len(path))])
|
|
|
|
class LoaderStrategy(object):
|
|
"""Describe the loading behavior of a StrategizedProperty object.
|
|
|
|
The ``LoaderStrategy`` interacts with the querying process in three
|
|
ways:
|
|
|
|
* it controls the configuration of the ``InstrumentedAttribute``
|
|
placed on a class to handle the behavior of the attribute. this
|
|
may involve setting up class-level callable functions to fire
|
|
off a select operation when the attribute is first accessed
|
|
(i.e. a lazy load)
|
|
|
|
* 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
|
|
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.
|
|
"""
|
|
|
|
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
|
|
|
|
def init(self):
|
|
raise NotImplementedError("LoaderStrategy")
|
|
|
|
def init_class_attribute(self, mapper):
|
|
pass
|
|
|
|
def setup_query(self, context, entity, path, adapter, **kwargs):
|
|
pass
|
|
|
|
def create_row_processor(self, selectcontext, path, mapper,
|
|
row, adapter):
|
|
"""Return row processing functions which fulfill the contract
|
|
specified by MapperProperty.create_row_processor.
|
|
|
|
StrategizedProperty delegates its create_row_processor method
|
|
directly to this method. """
|
|
|
|
raise NotImplementedError()
|
|
|
|
def __str__(self):
|
|
return str(self.parent_property)
|
|
|
|
def debug_callable(self, fn, logger, announcement, logfn):
|
|
if announcement:
|
|
logger.debug(announcement)
|
|
if logfn:
|
|
def call(*args, **kwargs):
|
|
logger.debug(logfn(*args, **kwargs))
|
|
return fn(*args, **kwargs)
|
|
return call
|
|
else:
|
|
return fn
|
|
|
|
class InstrumentationManager(object):
|
|
"""User-defined class instrumentation extension.
|
|
|
|
The API for this class should be considered as semi-stable,
|
|
and may change slightly with new releases.
|
|
|
|
"""
|
|
|
|
# r4361 added a mandatory (cls) constructor to this interface.
|
|
# given that, perhaps class_ should be dropped from all of these
|
|
# signatures.
|
|
|
|
def __init__(self, class_):
|
|
pass
|
|
|
|
def manage(self, class_, manager):
|
|
setattr(class_, '_default_class_manager', manager)
|
|
|
|
def dispose(self, class_, manager):
|
|
delattr(class_, '_default_class_manager')
|
|
|
|
def manager_getter(self, class_):
|
|
def get(cls):
|
|
return cls._default_class_manager
|
|
return get
|
|
|
|
def instrument_attribute(self, class_, key, inst):
|
|
pass
|
|
|
|
def post_configure_attribute(self, class_, key, inst):
|
|
pass
|
|
|
|
def install_descriptor(self, class_, key, inst):
|
|
setattr(class_, key, inst)
|
|
|
|
def uninstall_descriptor(self, class_, key):
|
|
delattr(class_, key)
|
|
|
|
def install_member(self, class_, key, implementation):
|
|
setattr(class_, key, implementation)
|
|
|
|
def uninstall_member(self, class_, key):
|
|
delattr(class_, key)
|
|
|
|
def instrument_collection_class(self, class_, key, collection_class):
|
|
global collections
|
|
if collections is None:
|
|
from sqlalchemy.orm import collections
|
|
return collections.prepare_instrumentation(collection_class)
|
|
|
|
def get_instance_dict(self, class_, instance):
|
|
return instance.__dict__
|
|
|
|
def initialize_instance_dict(self, class_, instance):
|
|
pass
|
|
|
|
def install_state(self, class_, instance, state):
|
|
setattr(instance, '_default_state', state)
|
|
|
|
def remove_state(self, class_, instance):
|
|
delattr(instance, '_default_state', state)
|
|
|
|
def state_getter(self, class_):
|
|
return lambda instance: getattr(instance, '_default_state')
|
|
|
|
def dict_getter(self, class_):
|
|
return lambda inst: self.get_instance_dict(class_, inst)
|
|
|