U a7@shdZddlmZddlmZdgZdddZddZd d Zd d Zd dZ Gddde Z ddZ dS)aA 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:`_orm.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:`_orm.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. Operations that are unsupported or are problematic include: * two entries must trade values. This is not supported directly in the case of a primary key or unique constraint because it means at least one row would need to be temporarily removed first, or changed to a third, neutral value while the switch occurs. * an entry must be deleted in order to make room for a new entry. SQLAlchemy's unit of work performs all INSERTs before DELETEs within a single flush. In the case of a primary key, it will trade an INSERT/DELETE of the same primary key for an UPDATE statement in order to lessen the impact of this limitation, however this does not take place for a UNIQUE column. A future feature will allow the "DELETE before INSERT" behavior to be possible, alleviating this limitation, though this feature will require explicit configuration at the mapper level for sets of columns that are to be handled in this way. :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``. ) collection)collection_adapter ordering_listNc s tfd|ifddS)aPrepares 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. count_fromcs tfSN) OrderingListattrkwr\C:\Users\vtejo\AppData\Local\Temp\pip-unpacked-wheel-nyjtotrf\sqlalchemy\ext\orderinglist.pyzordering_list..)_unsugar_count_from)r rr rr r rscCs|S)z7Numbering function: consecutive integers starting at 0.rindexrrrr count_from_0srcCs|dS)z7Numbering function: consecutive integers starting at 1.rrrrr count_from_1srcs4fdd}zd|_Wntk r.YnX|S)zENumbering function: consecutive integers starting at arbitrary start.cs|Srrrstartrr fszcount_from_n_factory..fz count_from_%i)__name__ TypeError)rrrrr count_from_n_factorys  rcKsX|dd}|dddkrT|dk rT|dkr6t|d<n|dkrHt|d<n t||d<|S)zBuilds counting functions from keyword arguments. Keyword argument filter, prepares a simple ``ordering_func`` from a ``count_from`` argument, otherwise passes ``ordering_func`` on unchanged. rN ordering_funcr)popgetrrr)r rrrr rs    rcseZdZdZd%ddZddZdd Zd d ZeZd&d dZ fddZ fddZ e de Z fddZfddZd'fdd ZfddZfddZfdd Zfd!d"Zd#d$ZeeD]8\ZZeerejekrejseeereeeje_q[[ZS)(rzA 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:`_orm.relationship` function. NFcCs"||_|dkrt}||_||_dS)a 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. N) ordering_attrrrreorder_on_append)selfrrr rrr __init__s 4zOrderingList.__init__cCs t||jSr)getattrrr!entityrrr _get_order_valueszOrderingList._get_order_valuecCst||j|dSr)setattrr)r!r%valuerrr _set_order_valueszOrderingList._set_order_valuecCs$t|D]\}}|||dqdS)zSynchronize ordering for the entire collection. Sweeps through the list and ensures that each object has accurate ordering information set. TN) enumerate _order_entityr!rr%rrr reorderszOrderingList.reorderTcCs>||}|dk r|sdS|||}||kr:|||dSr)r&rr))r!rr%r-ZhaveZ should_berrr r+*s    zOrderingList._order_entitycs,tt|||t|d||jdS)Nr)superrappendr+lenr r$ __class__rr r/5szOrderingList.appendcstt||dS)z%Append without any ordering behavior.N)r.rr/r$r1rr _raw_append9szOrderingList._raw_appendrcstt||||dSr)r.rinsert_reorderr,r1rr r4@szOrderingList.insertcs.tt||t|}|r*|jr*|dSr)r.rremoverZ_referenced_by_ownerr5)r!r%adapterr1rr r6Ds zOrderingList.removecstt||}||Sr)r.rrr5r,r1rr rKszOrderingList.popcst|trx|jpd}|jpd}|dkr2|t|7}|jp>t|}|dkrT|t|7}t|||D]}||||q`n |||dt t |||dS)NrrT) isinstanceslicesteprr0stoprange __setitem__r+r.r)r!rr%r;rr<ir1rr r>Ps     zOrderingList.__setitem__cstt|||dSr)r.r __delitem__r5)r!rr1rr r@`szOrderingList.__delitem__cs tt|||||dSr)r.r __setslice__r5)r!rendvaluesr1rr rAdszOrderingList.__setslice__cstt||||dSr)r.r __delslice__r5)r!rrBr1rr rDhszOrderingList.__delslice__cCst|j|jt|ffSr) _reconstituter2__dict__list)r!rrr __reduce__lszOrderingList.__reduce__)NNF)T)r8)r __module__ __qualname____doc__r"r&r)r-r5r+r/r3rZaddsr4r6rr>r@rArDrHrGlocalsitems func_namefunccallablehasattrr# __classcell__rrr1r rs@ <         rcCs&||}|j|t|||S)zReconstitute an :class:`.OrderingList`. This is the adjoint to :meth:`.OrderingList.__reduce__`. It is used for unpickling :class:`.OrderingList` objects. )__new__rFupdaterGextend)clsZdict_rMobjrrr rEzs   rE)N) rKZorm.collectionsrr__all__rrrrrrGrrErrrr sr   & )