170693cf0b
For the following structure:
class Playlist(Document):
items = ListField(EmbeddedDocumentField("PlaylistItem"))
class PlaylistItem(EmbeddedDocument):
song = ReferenceField("Song")
class Song(Document):
title = StringField()
this patch prevents the N+1 queries otherwise required to fetch all
the `Song` instances referenced by all the `PlaylistItem`s.
228 lines
10 KiB
Python
228 lines
10 KiB
Python
from bson import DBRef, SON
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from base import (BaseDict, BaseList, TopLevelDocumentMetaclass, get_document)
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from fields import (ReferenceField, ListField, DictField, MapField)
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from connection import get_db
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from queryset import QuerySet
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from document import Document, EmbeddedDocument
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class DeReference(object):
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def __call__(self, items, max_depth=1, instance=None, name=None):
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"""
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Cheaply dereferences the items to a set depth.
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Also handles the conversion of complex data types.
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:param items: The iterable (dict, list, queryset) to be dereferenced.
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:param max_depth: The maximum depth to recurse to
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:param instance: The owning instance used for tracking changes by
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:class:`~mongoengine.base.ComplexBaseField`
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:param name: The name of the field, used for tracking changes by
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:class:`~mongoengine.base.ComplexBaseField`
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:param get: A boolean determining if being called by __get__
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"""
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if items is None or isinstance(items, basestring):
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return items
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# cheapest way to convert a queryset to a list
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# list(queryset) uses a count() query to determine length
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if isinstance(items, QuerySet):
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items = [i for i in items]
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self.max_depth = max_depth
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doc_type = None
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if instance and isinstance(instance, (Document, EmbeddedDocument,
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TopLevelDocumentMetaclass)):
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doc_type = instance._fields.get(name)
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while hasattr(doc_type, 'field'):
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doc_type = doc_type.field
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if isinstance(doc_type, ReferenceField):
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field = doc_type
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doc_type = doc_type.document_type
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is_list = not hasattr(items, 'items')
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if is_list and all([i.__class__ == doc_type for i in items]):
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return items
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elif not is_list and all([i.__class__ == doc_type
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for i in items.values()]):
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return items
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elif not field.dbref:
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if not hasattr(items, 'items'):
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def _get_items(items):
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new_items = []
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for v in items:
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if isinstance(v, list):
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new_items.append(_get_items(v))
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elif not isinstance(v, (DBRef, Document)):
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new_items.append(field.to_python(v))
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else:
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new_items.append(v)
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return new_items
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items = _get_items(items)
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else:
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items = dict([
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(k, field.to_python(v))
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if not isinstance(v, (DBRef, Document)) else (k, v)
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for k, v in items.iteritems()]
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)
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self.reference_map = self._find_references(items)
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self.object_map = self._fetch_objects(doc_type=doc_type)
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return self._attach_objects(items, 0, instance, name)
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def _find_references(self, items, depth=0):
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"""
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Recursively finds all db references to be dereferenced
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:param items: The iterable (dict, list, queryset)
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:param depth: The current depth of recursion
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"""
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reference_map = {}
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if not items or depth >= self.max_depth:
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return reference_map
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# Determine the iterator to use
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if not hasattr(items, 'items'):
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iterator = enumerate(items)
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else:
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iterator = items.iteritems()
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# Recursively find dbreferences
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depth += 1
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for k, item in iterator:
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if isinstance(item, (Document, EmbeddedDocument)):
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for field_name, field in item._fields.iteritems():
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v = item._data.get(field_name, None)
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if isinstance(v, (DBRef)):
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reference_map.setdefault(field.document_type, []).append(v.id)
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elif isinstance(v, (dict, SON)) and '_ref' in v:
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reference_map.setdefault(get_document(v['_cls']), []).append(v['_ref'].id)
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elif isinstance(v, (dict, list, tuple)) and depth <= self.max_depth:
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field_cls = getattr(getattr(field, 'field', None), 'document_type', None)
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references = self._find_references(v, depth)
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for key, refs in references.iteritems():
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if isinstance(field_cls, (Document, TopLevelDocumentMetaclass)):
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key = field_cls
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reference_map.setdefault(key, []).extend(refs)
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elif isinstance(item, (DBRef)):
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reference_map.setdefault(item.collection, []).append(item.id)
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elif isinstance(item, (dict, SON)) and '_ref' in item:
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reference_map.setdefault(get_document(item['_cls']), []).append(item['_ref'].id)
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elif isinstance(item, (dict, list, tuple)) and depth - 1 <= self.max_depth:
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references = self._find_references(item, depth - 1)
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for key, refs in references.iteritems():
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reference_map.setdefault(key, []).extend(refs)
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return reference_map
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def _fetch_objects(self, doc_type=None):
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"""Fetch all references and convert to their document objects
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"""
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object_map = {}
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for collection, dbrefs in self.reference_map.iteritems():
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keys = object_map.keys()
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refs = list(set([dbref for dbref in dbrefs if unicode(dbref).encode('utf-8') not in keys]))
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if hasattr(collection, 'objects'): # We have a document class for the refs
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references = collection.objects.in_bulk(refs)
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for key, doc in references.iteritems():
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object_map[key] = doc
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else: # Generic reference: use the refs data to convert to document
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if isinstance(doc_type, (ListField, DictField, MapField,)):
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continue
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if doc_type:
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references = doc_type._get_db()[collection].find({'_id': {'$in': refs}})
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for ref in references:
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doc = doc_type._from_son(ref)
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object_map[doc.id] = doc
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else:
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references = get_db()[collection].find({'_id': {'$in': refs}})
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for ref in references:
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if '_cls' in ref:
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doc = get_document(ref["_cls"])._from_son(ref)
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elif doc_type is None:
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doc = get_document(
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''.join(x.capitalize()
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for x in collection.split('_')))._from_son(ref)
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else:
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doc = doc_type._from_son(ref)
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object_map[doc.id] = doc
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return object_map
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def _attach_objects(self, items, depth=0, instance=None, name=None):
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"""
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Recursively finds all db references to be dereferenced
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:param items: The iterable (dict, list, queryset)
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:param depth: The current depth of recursion
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:param instance: The owning instance used for tracking changes by
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:class:`~mongoengine.base.ComplexBaseField`
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:param name: The name of the field, used for tracking changes by
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:class:`~mongoengine.base.ComplexBaseField`
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"""
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if not items:
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if isinstance(items, (BaseDict, BaseList)):
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return items
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if instance:
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if isinstance(items, dict):
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return BaseDict(items, instance, name)
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else:
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return BaseList(items, instance, name)
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if isinstance(items, (dict, SON)):
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if '_ref' in items:
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return self.object_map.get(items['_ref'].id, items)
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elif '_cls' in items:
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doc = get_document(items['_cls'])._from_son(items)
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doc._data = self._attach_objects(doc._data, depth, doc, None)
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return doc
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if not hasattr(items, 'items'):
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is_list = True
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as_tuple = isinstance(items, tuple)
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iterator = enumerate(items)
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data = []
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else:
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is_list = False
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iterator = items.iteritems()
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data = {}
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depth += 1
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for k, v in iterator:
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if is_list:
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data.append(v)
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else:
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data[k] = v
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if k in self.object_map and not is_list:
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data[k] = self.object_map[k]
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elif isinstance(v, (Document, EmbeddedDocument)):
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for field_name, field in v._fields.iteritems():
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v = data[k]._data.get(field_name, None)
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if isinstance(v, (DBRef)):
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data[k]._data[field_name] = self.object_map.get(v.id, v)
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elif isinstance(v, (dict, SON)) and '_ref' in v:
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data[k]._data[field_name] = self.object_map.get(v['_ref'].id, v)
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elif isinstance(v, dict) and depth <= self.max_depth:
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data[k]._data[field_name] = self._attach_objects(v, depth, instance=instance, name=name)
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elif isinstance(v, (list, tuple)) and depth <= self.max_depth:
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data[k]._data[field_name] = self._attach_objects(v, depth, instance=instance, name=name)
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elif isinstance(v, (dict, list, tuple)) and depth <= self.max_depth:
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item_name = '%s.%s' % (name, k) if name else name
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data[k] = self._attach_objects(v, depth - 1, instance=instance, name=item_name)
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elif hasattr(v, 'id'):
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data[k] = self.object_map.get(v.id, v)
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if instance and name:
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if is_list:
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return tuple(data) if as_tuple else BaseList(data, instance, name)
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return BaseDict(data, instance, name)
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depth += 1
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return data
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