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dependency.py

# orm/dependency.py
# Copyright (C) 2005,2006 Michael Bayer mike_mp@zzzcomputing.com
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php


"""bridges the PropertyLoader (i.e. a relation()) and the UOWTransaction 
together to allow processing of scalar- and list-based dependencies at flush time."""

from sqlalchemy.orm import sync
from sqlalchemy.orm.sync import ONETOMANY,MANYTOONE,MANYTOMANY
from sqlalchemy import sql, util
from sqlalchemy.orm import session as sessionlib

def create_dependency_processor(prop):
    types = {
        ONETOMANY : OneToManyDP,
        MANYTOONE: ManyToOneDP,
        MANYTOMANY : ManyToManyDP,
    }
    if prop.association is not None:
        return AssociationDP(prop)
    else:
        return types[prop.direction](prop)

class DependencyProcessor(object):
    def __init__(self, prop):
        self.prop = prop
        self.cascade = prop.cascade
        self.mapper = prop.mapper
        self.parent = prop.parent
        self.association = prop.association
        self.secondary = prop.secondary
        self.direction = prop.direction
        self.is_backref = prop.is_backref
        self.post_update = prop.post_update
        self.foreignkey = prop.foreignkey
        self.passive_deletes = prop.passive_deletes
        self.key = prop.key

        self._compile_synchronizers()

    def register_dependencies(self, uowcommit):
        """tells a UOWTransaction what mappers are dependent on which, with regards
        to the two or three mappers handled by this PropertyLoader.

        Also registers itself as a "processor" for one of its mappers, which
        will be executed after that mapper's objects have been saved or before
        they've been deleted.  The process operation manages attributes and dependent
        operations upon the objects of one of the involved mappers."""
        raise NotImplementedError()

    def whose_dependent_on_who(self, obj1, obj2):
        """given an object pair assuming obj2 is a child of obj1, returns a tuple
        with the dependent object second, or None if they are equal.  
        used by objectstore's object-level topological sort (i.e. cyclical 
        table dependency)."""
        if obj1 is obj2:
            return None
        elif self.direction == ONETOMANY:
            return (obj1, obj2)
        else:
            return (obj2, obj1)
            
    def process_dependencies(self, task, deplist, uowcommit, delete = False):
        """this method is called during a flush operation to synchronize data between a parent and child object.
        it is called within the context of the various mappers and sometimes individual objects sorted according to their
        insert/update/delete order (topological sort)."""
        raise NotImplementedError()

    def preprocess_dependencies(self, task, deplist, uowcommit, delete = False):
        """used before the flushes' topological sort to traverse through related objects and insure every 
        instance which will require save/update/delete is properly added to the UOWTransaction."""
        raise NotImplementedError()

    def _synchronize(self, obj, child, associationrow, clearkeys):
        """called during a flush to synchronize primary key identifier values between a parent/child object, as well as 
        to an associationrow in the case of many-to-many."""
        raise NotImplementedError()

    def _compile_synchronizers(self):
        """assembles a list of 'synchronization rules', which are instructions on how to populate
        the objects on each side of a relationship.  This is done when a DependencyProcessor is 
        first initialized.

        The list of rules is used within commits by the _synchronize() method when dependent 
        objects are processed."""
        self.syncrules = sync.ClauseSynchronizer(self.parent, self.mapper, self.direction)
        if self.direction == sync.MANYTOMANY:
            self.syncrules.compile(self.prop.primaryjoin, issecondary=False)
            self.syncrules.compile(self.prop.secondaryjoin, issecondary=True)
        else:
            self.syncrules.compile(self.prop.primaryjoin, foreignkey=self.foreignkey)
        
    def get_object_dependencies(self, obj, uowcommit, passive = True):
        """returns the list of objects that are dependent on the given object, as according to the relationship
        this dependency processor represents"""
        return sessionlib.attribute_manager.get_history(obj, self.key, passive = passive)

    def _conditional_post_update(self, obj, uowcommit, related):
        """execute a post_update call.
        
        for relations that contain the post_update flag, an additional UPDATE statement may be
        associated after an INSERT or before a DELETE in order to resolve circular row dependencies.
        This method will check for the post_update flag being set on a particular relationship, and
        given a target object and list of one or more related objects, and execute the UPDATE if the
        given related object list contains INSERTs or DELETEs."""
        if obj is not None and self.post_update:
            for x in related:
                if x is not None and (uowcommit.is_deleted(x) or not hasattr(x, '_instance_key')):
                    uowcommit.register_object(obj, postupdate=True, post_update_cols=self.syncrules.dest_columns())
                    break

class OneToManyDP(DependencyProcessor):
    def register_dependencies(self, uowcommit):
        if self.post_update:
            stub = MapperStub(self.parent, self.mapper, self.key)
            uowcommit.register_dependency(self.mapper, stub)
            uowcommit.register_dependency(self.parent, stub)
            uowcommit.register_processor(stub, self, self.parent)
        else:
            uowcommit.register_dependency(self.parent, self.mapper)
            uowcommit.register_processor(self.parent, self, self.parent)
    def process_dependencies(self, task, deplist, uowcommit, delete = False):
        #print self.mapper.mapped_table.name + " " + self.key + " " + repr(len(deplist)) + " process_dep isdelete " + repr(delete) + " direction " + repr(self.direction)
        if delete:
            # head object is being deleted, and we manage its list of child objects
            # the child objects have to have their foreign key to the parent set to NULL
            if not self.cascade.delete_orphan or self.post_update:
                for obj in deplist:
                    childlist = self.get_object_dependencies(obj, uowcommit, passive=False)
                    for child in childlist.deleted_items():
                        if child is not None and childlist.hasparent(child) is False:
                            self._synchronize(obj, child, None, True)
                            self._conditional_post_update(child, uowcommit, [obj])
                    for child in childlist.unchanged_items():
                        if child is not None:
                            self._synchronize(obj, child, None, True)
                            self._conditional_post_update(child, uowcommit, [obj])
        else:
            for obj in deplist:
                childlist = self.get_object_dependencies(obj, uowcommit, passive=True)
                if childlist is not None:
                    for child in childlist.added_items():
                        self._synchronize(obj, child, None, False)
                        self._conditional_post_update(child, uowcommit, [obj])
                    for child in childlist.deleted_items():
                        if not self.cascade.delete_orphan:
                            self._synchronize(obj, child, None, True)

    def preprocess_dependencies(self, task, deplist, uowcommit, delete = False):
        #print self.mapper.mapped_table.name + " " + self.key + " " + repr(len(deplist)) + " preprocess_dep isdelete " + repr(delete) + " direction " + repr(self.direction)

        if delete:
            # head object is being deleted, and we manage its list of child objects
            # the child objects have to have their foreign key to the parent set to NULL
            if self.post_update:
                pass
            elif self.cascade.delete_orphan:
                for obj in deplist:
                    childlist = self.get_object_dependencies(obj, uowcommit, passive=False)
                    for child in childlist.deleted_items():
                        if child is not None and childlist.hasparent(child) is False:
                            uowcommit.register_object(child, isdelete=True)
                            for c in self.mapper.cascade_iterator('delete', child):
                                uowcommit.register_object(c, isdelete=True)
                    for child in childlist.unchanged_items():
                        if child is not None:
                            uowcommit.register_object(child, isdelete=True)
                            for c in self.mapper.cascade_iterator('delete', child):
                                uowcommit.register_object(c, isdelete=True)
            else:
                for obj in deplist:
                    childlist = self.get_object_dependencies(obj, uowcommit, passive=False)
                    for child in childlist.deleted_items():
                        if child is not None and childlist.hasparent(child) is False:
                            uowcommit.register_object(child)
                    for child in childlist.unchanged_items():
                        if child is not None:
                            uowcommit.register_object(child)
        else:
            for obj in deplist:
                childlist = self.get_object_dependencies(obj, uowcommit, passive=True)
                if childlist is not None:
                    for child in childlist.added_items():
                        if child is not None:
                            uowcommit.register_object(child)
                    for child in childlist.deleted_items():
                        if not self.cascade.delete_orphan:
                            uowcommit.register_object(child, isdelete=False)
                        elif childlist.hasparent(child) is False:
                            uowcommit.register_object(child, isdelete=True)
                            for c in self.mapper.cascade_iterator('delete', child):
                                uowcommit.register_object(c, isdelete=True)
            
    def _synchronize(self, obj, child, associationrow, clearkeys):
        source = obj
        dest = child
        if dest is None:
            return
        self.syncrules.execute(source, dest, obj, child, clearkeys)
    
class ManyToOneDP(DependencyProcessor):
    def register_dependencies(self, uowcommit):
        if self.post_update:
            stub = MapperStub(self.parent, self.mapper, self.key)
            uowcommit.register_dependency(self.mapper, stub)
            uowcommit.register_dependency(self.parent, stub)
            uowcommit.register_processor(stub, self, self.parent)
        else:
            uowcommit.register_dependency(self.mapper, self.parent)
            uowcommit.register_processor(self.mapper, self, self.parent)
    def process_dependencies(self, task, deplist, uowcommit, delete = False):
        #print self.mapper.mapped_table.name + " " + self.key + " " + repr(len(deplist)) + " process_dep isdelete " + repr(delete) + " direction " + repr(self.direction)
        if delete:
            if self.post_update and not self.cascade.delete_orphan:
                # post_update means we have to update our row to not reference the child object
                # before we can DELETE the row
                for obj in deplist:
                    self._synchronize(obj, None, None, True)
                    childlist = self.get_object_dependencies(obj, uowcommit, passive=False)
                    self._conditional_post_update(obj, uowcommit, childlist.deleted_items() + childlist.unchanged_items() + childlist.added_items())
        else:
            for obj in deplist:
                childlist = self.get_object_dependencies(obj, uowcommit, passive=True)
                if childlist is not None:
                    for child in childlist.added_items():
                        self._synchronize(obj, child, None, False)
                    self._conditional_post_update(obj, uowcommit, childlist.deleted_items() + childlist.unchanged_items() + childlist.added_items())
                        
    def preprocess_dependencies(self, task, deplist, uowcommit, delete = False):
        #print self.mapper.mapped_table.name + " " + self.key + " " + repr(len(deplist)) + " PRE process_dep isdelete " + repr(delete) + " direction " + repr(self.direction)
        if self.post_update:
            return
        if delete:
            if self.cascade.delete:
                for obj in deplist:
                    childlist = self.get_object_dependencies(obj, uowcommit, passive=False)
                    for child in childlist.deleted_items() + childlist.unchanged_items():
                        if child is not None and childlist.hasparent(child) is False:
                            uowcommit.register_object(child, isdelete=True)
                            for c in self.mapper.cascade_iterator('delete', child):
                                uowcommit.register_object(c, isdelete=True)
        else:
            for obj in deplist:
                uowcommit.register_object(obj)
                if self.cascade.delete_orphan:
                    childlist = self.get_object_dependencies(obj, uowcommit, passive=False)
                    for child in childlist.deleted_items():
                        if childlist.hasparent(child) is False:
                            uowcommit.register_object(child, isdelete=True)
                            for c in self.mapper.cascade_iterator('delete', child):
                                uowcommit.register_object(c, isdelete=True)
                        
    def _synchronize(self, obj, child, associationrow, clearkeys):
        source = child
        dest = obj
        if dest is None:
            return
        self.syncrules.execute(source, dest, obj, child, clearkeys)

class ManyToManyDP(DependencyProcessor):
    def register_dependencies(self, uowcommit):
        # many-to-many.  create a "Stub" mapper to represent the
        # "middle table" in the relationship.  This stub mapper doesnt save
        # or delete any objects, but just marks a dependency on the two
        # related mappers.  its dependency processor then populates the
        # association table.

        if self.is_backref:
            # if we are the "backref" half of a two-way backref 
            # relationship, let the other mapper handle inserting the rows
            return
        stub = MapperStub(self.parent, self.mapper, self.key)
        uowcommit.register_dependency(self.parent, stub)
        uowcommit.register_dependency(self.mapper, stub)
        uowcommit.register_processor(stub, self, self.parent)
        
    def process_dependencies(self, task, deplist, uowcommit, delete = False):
        #print self.mapper.table.name + " " + self.key + " " + repr(len(deplist)) + " process_dep isdelete " + repr(delete) + " direction " + repr(self.direction)
        connection = uowcommit.transaction.connection(self.mapper)
        secondary_delete = []
        secondary_insert = []
        if delete:
            for obj in deplist:
                childlist = self.get_object_dependencies(obj, uowcommit, passive=False)
                for child in childlist.deleted_items() + childlist.unchanged_items():
                    associationrow = {}
                    self._synchronize(obj, child, associationrow, False)
                    secondary_delete.append(associationrow)
        else:
            for obj in deplist:
                childlist = self.get_object_dependencies(obj, uowcommit)
                if childlist is None: continue
                for child in childlist.added_items():
                    associationrow = {}
                    self._synchronize(obj, child, associationrow, False)
                    secondary_insert.append(associationrow)
                for child in childlist.deleted_items():
                    associationrow = {}
                    self._synchronize(obj, child, associationrow, False)
                    secondary_delete.append(associationrow)
        if len(secondary_delete):
            secondary_delete.sort()
            # TODO: precompile the delete/insert queries?
            statement = self.secondary.delete(sql.and_(*[c == sql.bindparam(c.key) for c in self.secondary.c if c.key in associationrow]))
            connection.execute(statement, secondary_delete)
        if len(secondary_insert):
            statement = self.secondary.insert()
            connection.execute(statement, secondary_insert)

    def preprocess_dependencies(self, task, deplist, uowcommit, delete = False):
        pass
    def _synchronize(self, obj, child, associationrow, clearkeys):
        dest = associationrow
        source = None
        if dest is None:
            return
        self.syncrules.execute(source, dest, obj, child, clearkeys)

class AssociationDP(OneToManyDP):
    def __init__(self, *args, **kwargs):
        super(AssociationDP, self).__init__(*args, **kwargs)
        self.cascade.delete = True
        self.cascade.delete_orphan = True

00328 class MapperStub(object):
    """poses as a Mapper representing the association table in a many-to-many
    join, when performing a flush().  

    The Task objects in the objectstore module treat it just like
    any other Mapper, but in fact it only serves as a "dependency" placeholder
    for the many-to-many update task."""
    __metaclass__ = util.ArgSingleton
    def __init__(self, parent, mapper, key):
        self.mapper = mapper
        self._inheriting_mappers = []
    def register_dependencies(self, uowcommit):
        pass
    def save_obj(self, *args, **kwargs):
        pass
    def delete_obj(self, *args, **kwargs):
        pass
    def primary_mapper(self):
        return self
    def base_mapper(self):
        return self

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