mirror of
https://github.com/janeczku/calibre-web
synced 2024-11-24 18:47:23 +00:00
368 lines
13 KiB
Python
368 lines
13 KiB
Python
# ext/orderinglist.py
|
|
# Copyright (C) 2005-2013 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
|
|
|
|
"""A custom list that manages index/position information for contained
|
|
elements.
|
|
|
|
:author: Jason Kirtland
|
|
|
|
``orderinglist`` is a helper for mutable ordered relationships. It will
|
|
intercept list operations performed on a :func:`.relationship`-managed
|
|
collection and
|
|
automatically synchronize changes in list position onto a target scalar
|
|
attribute.
|
|
|
|
Example: A ``slide`` table, where each row refers to zero or more entries
|
|
in a related ``bullet`` table. The bullets within a slide are
|
|
displayed in order based on the value of the ``position`` column in the
|
|
``bullet`` table. As entries are reordered in memory, the value of the
|
|
``position`` attribute should be updated to reflect the new sort order::
|
|
|
|
|
|
Base = declarative_base()
|
|
|
|
class Slide(Base):
|
|
__tablename__ = 'slide'
|
|
|
|
id = Column(Integer, primary_key=True)
|
|
name = Column(String)
|
|
|
|
bullets = relationship("Bullet", order_by="Bullet.position")
|
|
|
|
class Bullet(Base):
|
|
__tablename__ = 'bullet'
|
|
id = Column(Integer, primary_key=True)
|
|
slide_id = Column(Integer, ForeignKey('slide.id'))
|
|
position = Column(Integer)
|
|
text = Column(String)
|
|
|
|
The standard relationship mapping will produce a list-like attribute on each
|
|
``Slide`` containing all related ``Bullet`` objects,
|
|
but coping with changes in ordering is not handled automatically.
|
|
When appending a ``Bullet`` into ``Slide.bullets``, the ``Bullet.position``
|
|
attribute will remain unset until manually assigned. When the ``Bullet``
|
|
is inserted into the middle of the list, the following ``Bullet`` objects
|
|
will also need to be renumbered.
|
|
|
|
The :class:`.OrderingList` object automates this task, managing the
|
|
``position`` attribute on all ``Bullet`` objects in the collection. It is
|
|
constructed using the :func:`.ordering_list` factory::
|
|
|
|
from sqlalchemy.ext.orderinglist import ordering_list
|
|
|
|
Base = declarative_base()
|
|
|
|
class Slide(Base):
|
|
__tablename__ = 'slide'
|
|
|
|
id = Column(Integer, primary_key=True)
|
|
name = Column(String)
|
|
|
|
bullets = relationship("Bullet", order_by="Bullet.position",
|
|
collection_class=ordering_list('position'))
|
|
|
|
class Bullet(Base):
|
|
__tablename__ = 'bullet'
|
|
id = Column(Integer, primary_key=True)
|
|
slide_id = Column(Integer, ForeignKey('slide.id'))
|
|
position = Column(Integer)
|
|
text = Column(String)
|
|
|
|
With the above mapping the ``Bullet.position`` attribute is managed::
|
|
|
|
s = Slide()
|
|
s.bullets.append(Bullet())
|
|
s.bullets.append(Bullet())
|
|
s.bullets[1].position
|
|
>>> 1
|
|
s.bullets.insert(1, Bullet())
|
|
s.bullets[2].position
|
|
>>> 2
|
|
|
|
The :class:`.OrderingList` construct only works with **changes** to a collection,
|
|
and not the initial load from the database, and requires that the list be
|
|
sorted when loaded. Therefore, be sure to
|
|
specify ``order_by`` on the :func:`.relationship` against the target ordering
|
|
attribute, so that the ordering is correct when first loaded.
|
|
|
|
.. warning::
|
|
|
|
:class:`.OrderingList` only provides limited functionality when a primary
|
|
key column or unique column is the target of the sort. Since changing the
|
|
order of entries often means that two rows must trade values, this is not
|
|
possible when the value is constrained by a primary key or unique
|
|
constraint, since one of the rows would temporarily have to point to a
|
|
third available value so that the other row could take its old
|
|
value. :class:`.OrderingList` doesn't do any of this for you,
|
|
nor does SQLAlchemy itself.
|
|
|
|
:func:`.ordering_list` takes the name of the related object's ordering attribute as
|
|
an argument. By default, the zero-based integer index of the object's
|
|
position in the :func:`.ordering_list` is synchronized with the ordering attribute:
|
|
index 0 will get position 0, index 1 position 1, etc. To start numbering at 1
|
|
or some other integer, provide ``count_from=1``.
|
|
|
|
|
|
"""
|
|
from ..orm.collections import collection
|
|
from .. import util
|
|
|
|
__all__ = ['ordering_list']
|
|
|
|
|
|
def ordering_list(attr, count_from=None, **kw):
|
|
"""Prepares an :class:`OrderingList` factory for use in mapper definitions.
|
|
|
|
Returns an object suitable for use as an argument to a Mapper
|
|
relationship's ``collection_class`` option. e.g.::
|
|
|
|
from sqlalchemy.ext.orderinglist import ordering_list
|
|
|
|
class Slide(Base):
|
|
__tablename__ = 'slide'
|
|
|
|
id = Column(Integer, primary_key=True)
|
|
name = Column(String)
|
|
|
|
bullets = relationship("Bullet", order_by="Bullet.position",
|
|
collection_class=ordering_list('position'))
|
|
|
|
:param attr:
|
|
Name of the mapped attribute to use for storage and retrieval of
|
|
ordering information
|
|
|
|
:param count_from:
|
|
Set up an integer-based ordering, starting at ``count_from``. For
|
|
example, ``ordering_list('pos', count_from=1)`` would create a 1-based
|
|
list in SQL, storing the value in the 'pos' column. Ignored if
|
|
``ordering_func`` is supplied.
|
|
|
|
Additional arguments are passed to the :class:`.OrderingList` constructor.
|
|
|
|
"""
|
|
|
|
kw = _unsugar_count_from(count_from=count_from, **kw)
|
|
return lambda: OrderingList(attr, **kw)
|
|
|
|
|
|
# Ordering utility functions
|
|
|
|
|
|
def count_from_0(index, collection):
|
|
"""Numbering function: consecutive integers starting at 0."""
|
|
|
|
return index
|
|
|
|
|
|
def count_from_1(index, collection):
|
|
"""Numbering function: consecutive integers starting at 1."""
|
|
|
|
return index + 1
|
|
|
|
|
|
def count_from_n_factory(start):
|
|
"""Numbering function: consecutive integers starting at arbitrary start."""
|
|
|
|
def f(index, collection):
|
|
return index + start
|
|
try:
|
|
f.__name__ = 'count_from_%i' % start
|
|
except TypeError:
|
|
pass
|
|
return f
|
|
|
|
|
|
def _unsugar_count_from(**kw):
|
|
"""Builds counting functions from keyword arguments.
|
|
|
|
Keyword argument filter, prepares a simple ``ordering_func`` from a
|
|
``count_from`` argument, otherwise passes ``ordering_func`` on unchanged.
|
|
"""
|
|
|
|
count_from = kw.pop('count_from', None)
|
|
if kw.get('ordering_func', None) is None and count_from is not None:
|
|
if count_from == 0:
|
|
kw['ordering_func'] = count_from_0
|
|
elif count_from == 1:
|
|
kw['ordering_func'] = count_from_1
|
|
else:
|
|
kw['ordering_func'] = count_from_n_factory(count_from)
|
|
return kw
|
|
|
|
|
|
class OrderingList(list):
|
|
"""A custom list that manages position information for its children.
|
|
|
|
The :class:`.OrderingList` object is normally set up using the
|
|
:func:`.ordering_list` factory function, used in conjunction with
|
|
the :func:`.relationship` function.
|
|
|
|
"""
|
|
|
|
def __init__(self, ordering_attr=None, ordering_func=None,
|
|
reorder_on_append=False):
|
|
"""A custom list that manages position information for its children.
|
|
|
|
``OrderingList`` is a ``collection_class`` list implementation that
|
|
syncs position in a Python list with a position attribute on the
|
|
mapped objects.
|
|
|
|
This implementation relies on the list starting in the proper order,
|
|
so be **sure** to put an ``order_by`` on your relationship.
|
|
|
|
:param ordering_attr:
|
|
Name of the attribute that stores the object's order in the
|
|
relationship.
|
|
|
|
:param ordering_func: Optional. A function that maps the position in
|
|
the Python list to a value to store in the
|
|
``ordering_attr``. Values returned are usually (but need not be!)
|
|
integers.
|
|
|
|
An ``ordering_func`` is called with two positional parameters: the
|
|
index of the element in the list, and the list itself.
|
|
|
|
If omitted, Python list indexes are used for the attribute values.
|
|
Two basic pre-built numbering functions are provided in this module:
|
|
``count_from_0`` and ``count_from_1``. For more exotic examples
|
|
like stepped numbering, alphabetical and Fibonacci numbering, see
|
|
the unit tests.
|
|
|
|
:param reorder_on_append:
|
|
Default False. When appending an object with an existing (non-None)
|
|
ordering value, that value will be left untouched unless
|
|
``reorder_on_append`` is true. This is an optimization to avoid a
|
|
variety of dangerous unexpected database writes.
|
|
|
|
SQLAlchemy will add instances to the list via append() when your
|
|
object loads. If for some reason the result set from the database
|
|
skips a step in the ordering (say, row '1' is missing but you get
|
|
'2', '3', and '4'), reorder_on_append=True would immediately
|
|
renumber the items to '1', '2', '3'. If you have multiple sessions
|
|
making changes, any of whom happen to load this collection even in
|
|
passing, all of the sessions would try to "clean up" the numbering
|
|
in their commits, possibly causing all but one to fail with a
|
|
concurrent modification error.
|
|
|
|
Recommend leaving this with the default of False, and just call
|
|
``reorder()`` if you're doing ``append()`` operations with
|
|
previously ordered instances or when doing some housekeeping after
|
|
manual sql operations.
|
|
|
|
"""
|
|
self.ordering_attr = ordering_attr
|
|
if ordering_func is None:
|
|
ordering_func = count_from_0
|
|
self.ordering_func = ordering_func
|
|
self.reorder_on_append = reorder_on_append
|
|
|
|
# More complex serialization schemes (multi column, e.g.) are possible by
|
|
# subclassing and reimplementing these two methods.
|
|
def _get_order_value(self, entity):
|
|
return getattr(entity, self.ordering_attr)
|
|
|
|
def _set_order_value(self, entity, value):
|
|
setattr(entity, self.ordering_attr, value)
|
|
|
|
def reorder(self):
|
|
"""Synchronize ordering for the entire collection.
|
|
|
|
Sweeps through the list and ensures that each object has accurate
|
|
ordering information set.
|
|
|
|
"""
|
|
for index, entity in enumerate(self):
|
|
self._order_entity(index, entity, True)
|
|
|
|
# As of 0.5, _reorder is no longer semi-private
|
|
_reorder = reorder
|
|
|
|
def _order_entity(self, index, entity, reorder=True):
|
|
have = self._get_order_value(entity)
|
|
|
|
# Don't disturb existing ordering if reorder is False
|
|
if have is not None and not reorder:
|
|
return
|
|
|
|
should_be = self.ordering_func(index, self)
|
|
if have != should_be:
|
|
self._set_order_value(entity, should_be)
|
|
|
|
def append(self, entity):
|
|
super(OrderingList, self).append(entity)
|
|
self._order_entity(len(self) - 1, entity, self.reorder_on_append)
|
|
|
|
def _raw_append(self, entity):
|
|
"""Append without any ordering behavior."""
|
|
|
|
super(OrderingList, self).append(entity)
|
|
_raw_append = collection.adds(1)(_raw_append)
|
|
|
|
def insert(self, index, entity):
|
|
super(OrderingList, self).insert(index, entity)
|
|
self._reorder()
|
|
|
|
def remove(self, entity):
|
|
super(OrderingList, self).remove(entity)
|
|
self._reorder()
|
|
|
|
def pop(self, index=-1):
|
|
entity = super(OrderingList, self).pop(index)
|
|
self._reorder()
|
|
return entity
|
|
|
|
def __setitem__(self, index, entity):
|
|
if isinstance(index, slice):
|
|
step = index.step or 1
|
|
start = index.start or 0
|
|
if start < 0:
|
|
start += len(self)
|
|
stop = index.stop or len(self)
|
|
if stop < 0:
|
|
stop += len(self)
|
|
|
|
for i in xrange(start, stop, step):
|
|
self.__setitem__(i, entity[i])
|
|
else:
|
|
self._order_entity(index, entity, True)
|
|
super(OrderingList, self).__setitem__(index, entity)
|
|
|
|
def __delitem__(self, index):
|
|
super(OrderingList, self).__delitem__(index)
|
|
self._reorder()
|
|
|
|
# Py2K
|
|
def __setslice__(self, start, end, values):
|
|
super(OrderingList, self).__setslice__(start, end, values)
|
|
self._reorder()
|
|
|
|
def __delslice__(self, start, end):
|
|
super(OrderingList, self).__delslice__(start, end)
|
|
self._reorder()
|
|
# end Py2K
|
|
|
|
def __reduce__(self):
|
|
return _reconstitute, (self.__class__, self.__dict__, list(self))
|
|
|
|
for func_name, func in locals().items():
|
|
if (util.callable(func) and func.func_name == func_name and
|
|
not func.__doc__ and hasattr(list, func_name)):
|
|
func.__doc__ = getattr(list, func_name).__doc__
|
|
del func_name, func
|
|
|
|
|
|
def _reconstitute(cls, dict_, items):
|
|
""" Reconstitute an :class:`.OrderingList`.
|
|
|
|
This is the adjoint to :meth:`.OrderingList.__reduce__`. It is used for
|
|
unpickling :class:`.OrderingList` objects.
|
|
|
|
"""
|
|
obj = cls.__new__(cls)
|
|
obj.__dict__.update(dict_)
|
|
list.extend(obj, items)
|
|
return obj
|