Skip to content
This repository

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

file 157 lines (132 sloc) 5.558 kb
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157
# Copyright 2009 10gen, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Manipulators that can edit SON objects as they enter and exit a database.

New manipulators should be defined as subclasses of SONManipulator and can be
installed on a database by calling `pymongo.database.Database.add_son_manipulator`."""

import types

from objectid import ObjectId
from dbref import DBRef
from son import SON

class SONManipulator(object):
    """A base son manipulator.

This manipulator just saves and restores objects without changing them.
"""
    def will_copy(self):
        """Will this SON manipulator make a copy of the incoming document?

Derived classes that do need to make a copy should override this method,
returning True instead of False. All non-copying manipulators will be
applied first (so that the user's document will be updated
appropriately), followed by copying manipulators.
"""
        return False

    def transform_incoming(self, son, collection):
        """Manipulate an incoming SON object.

:Parameters:
- `son`: the SON object to be inserted into the database
- `collection`: the collection the object is being inserted into
"""
        if self.will_copy():
            return SON(son)
        return son

    def transform_outgoing(self, son, collection):
        """Manipulate an outgoing SON object.

:Parameters:
- `son`: the SON object being retrieved from the database
- `collection`: the collection this object was stored in
"""
        if self.will_copy():
            return SON(son)
        return son

class ObjectIdInjector(SONManipulator):
    """A son manipulator that adds the _id field if it is missing.
"""
    def transform_incoming(self, son, collection):
        """Add an _id field if it is missing.
"""
        if not "_id" in son:
            son["_id"] = ObjectId()
        return son

class ObjectIdShuffler(SONManipulator):
    """A son manipulator that moves _id to the first position.
"""
    def will_copy(self):
        """We need to copy to be sure that we are dealing with SON, not a dict.
"""
        return True

    def transform_incoming(self, son, collection):
        """Move _id to the front if it's there.
"""
        if not "_id" in son:
            return son
        transformed = SON({"_id": son["_id"]})
        transformed.update(son)
        return transformed

class NamespaceInjector(SONManipulator):
    """A son manipulator that adds the _ns field.
"""
    def transform_incoming(self, son, collection):
        """Add the _ns field to the incoming object
"""
        son["_ns"] = collection.name()
        return son

class AutoReference(SONManipulator):
    """Transparently reference and de-reference already saved embedded objects.

This manipulator should probably only be used when the NamespaceInjector is
also being used, otherwise it doesn't make too much sense - documents can
only be auto-referenced if they have an *_ns* field.
"""
    def __init__(self, db):
        self.__database = db

    def will_copy(self):
        """We need to copy so the user's document doesn't get transformed refs.
"""
        return True

    def transform_incoming(self, son, collection):
        """Replace embedded documents with DBRefs.
"""
        def transform_value(value):
            if isinstance(value, types.DictType):
                if "_id" in value and "_ns" in value:
                    return DBRef(value["_ns"], transform_value(value["_id"]))
                else:
                    return transform_dict(SON(value))
            elif isinstance(value, types.ListType):
                return [transform_value(v) for v in value]
            return value

        def transform_dict(object):
            for (key, value) in object.items():
                object[key] = transform_value(value)
            return object

        return transform_dict(SON(son))

    def transform_outgoing(self, son, collection):
        """Replace DBRefs with embedded documents.
"""
        def transform_value(value):
            if isinstance(value, DBRef):
                return self.__database.dereference(value)
            elif isinstance(value, types.ListType):
                return [transform_value(v) for v in value]
            elif isinstance(value, types.DictType):
                return transform_dict(SON(value))
            return value

        def transform_dict(object):
            for (key, value) in object.items():
                object[key] = transform_value(value)
            return object

        return transform_dict(SON(son))

# TODO make a generic translator for custom types. Take encode, decode,
# should_encode and should_decode functions and just encode and decode where
# necessary. See examples/custom_type.py for where this would be useful.
# Alternatively it could take a should_encode, to_binary, from_binary and
# binary subtype.
Something went wrong with that request. Please try again.