ODM Event Interfaces

This section describes the various categories of events which can be intercepted within the Ming ODM. Events can be trapped by registering MapperExtension and SessionExtension instances which implement the event handlers for the events you want to trap.

Mapper Events

Mapper events are used to track To use MapperExtension, make your own subclass of it and just send it off to a mapper:

from ming.odm.mapper import MapperExtension
class MyExtension(MapperExtension):
    def after_insert(self, obj, st, sess):
        print "instance %s after insert !" % obj

class MyMappedClass(MappedClass):
    class __mongometa__:
        session = session
        name = 'my_mapped_class'
        extensions = [ MyExtension ]

Multiple extensions will be chained together and processed in order;

extensions = [ext1, ext2, ext3]

class ming.odm.MapperExtension(mapper)

Base class that should be inherited to handle Mapper events.

after_delete(instance, state, sess)

Receive an object instance and its current state after that instance is deleted.

after_insert(instance, state, sess)

Receive an object instance and its current state after that instance is inserted into its collection.

after_remove(sess, *args, **kwargs)

After a remove query is performed for this class

after_update(instance, state, sess)

Receive an object instance and its current state after that instance is updated.

before_delete(instance, state, sess)

Receive an object instance and its current state before that instance is deleted.

before_insert(instance, state, sess)

Receive an object instance and its current state before that instance is inserted into its collection.

before_remove(sess, *args, **kwargs)

Before a remove query is performed for this class

before_update(instance, state, sess)

Receive an object instance and its current state before that instance is updated.

Session Events

The SessionExtension applies plugin points for Session objects and ODMCursor objects:

from ming.odm.base import state
from ming.odm.odmsession import SessionExtension

class MySessionExtension(SessionExtension):
    def __init__(self, session):
        SessionExtension.__init__(self, session)
        self.objects_added = []
        self.objects_modified = []
        self.objects_deleted = []

    def before_flush(self, obj=None):
        if obj is None:
            self.objects_added = list(self.session.uow.new)
            self.objects_modified = list(self.session.uow.dirty)
            self.objects_deleted = list(self.session.uow.deleted)
        # do something

ODMSession = ThreadLocalODMSession(session,
                                   extensions=[ProjectSessionExtension])

The same SessionExtension instance can be used with any number of sessions. It is possible to register extensions on an already created ODMSession using the register_extension(extension) method of the session itself. Even calling register_extension it is possible to register the extensions only before using the session for the first time.

class ming.odm.SessionExtension(session)

Base class that should be inherited to handle Session events.

after_cursor_next(cursor)

Cursor has advanced to next result

after_delete(obj, st)

After an object gets deleted in this session

after_flush(obj=None)

After the session is flushed for obj

If obj is None it means all the objects in the UnitOfWork which can be retrieved by iterating over ODMSession.uow

after_insert(obj, st)

After an object gets inserted in this session

after_remove(cls, *args, **kwargs)

After a remove query is performed session

after_update(obj, st)

After an object gets updated in this session

before_cursor_next(cursor)

Cursor is going to advance to next result

before_delete(obj, st)

Before an object gets deleted in this session

before_flush(obj=None)

Before the session is flushed for obj

If obj is None it means all the objects in the UnitOfWork which can be retrieved by iterating over ODMSession.uow

before_insert(obj, st)

Before an object gets inserted in this session

before_remove(cls, *args, **kwargs)

Before a remove query is performed session

before_update(obj, st)

Before an object gets updated in this session

cursor_created(cursor, action, *args, **kw)

New cursor with the results of a query got created