diff options
| -rw-r--r-- | django/db/models/query.py | 30 |
1 files changed, 21 insertions, 9 deletions
diff --git a/django/db/models/query.py b/django/db/models/query.py index 1461125af4..be42d02006 100644 --- a/django/db/models/query.py +++ b/django/db/models/query.py @@ -3,6 +3,7 @@ The main QuerySet implementation. This provides the public API for the ORM. """ import copy +import itertools from django.db import connections, router, transaction, IntegrityError from django.db.models.fields import AutoField @@ -1574,9 +1575,12 @@ def prefetch_related_objects(result_cache, related_lookups): # ensure we don't do duplicate work. done_lookups = set() # list of lookups like foo__bar__baz done_queries = {} # dictionary of things like 'foo__bar': [results] - related_lookups = list(related_lookups) - # We may expand related_lookups, so need a loop that allows for that + manual_lookups = list(related_lookups) + auto_lookups = [] # we add to this as we go through. + followed_descriptors = set() # recursion protection + + related_lookups = itertools.chain(manual_lookups, auto_lookups) for lookup in related_lookups: if lookup in done_lookups: # We've done exactly this already, skip the whole thing @@ -1616,7 +1620,7 @@ def prefetch_related_objects(result_cache, related_lookups): # We assume that objects retrieved are homogenous (which is the premise # of prefetch_related), so what applies to first object applies to all. first_obj = obj_list[0] - prefetcher, attr_found, is_fetched = get_prefetcher(first_obj, attr) + prefetcher, descriptor, attr_found, is_fetched = get_prefetcher(first_obj, attr) if not attr_found: raise AttributeError("Cannot find '%s' on %s object, '%s' is an invalid " @@ -1638,10 +1642,17 @@ def prefetch_related_objects(result_cache, related_lookups): obj_list = done_queries[current_lookup] else: obj_list, additional_prl = prefetch_one_level(obj_list, prefetcher, attr) - for f in additional_prl: - new_prl = LOOKUP_SEP.join([current_lookup, f]) - related_lookups.append(new_prl) - done_queries[current_lookup] = obj_list + # We need to ensure we don't keep adding lookups from the + # same relationships to stop infinite recursion. So, if we + # are already on an automatically added lookup, don't add + # the new lookups from relationships we've seen already. + if not (lookup in auto_lookups and + descriptor in followed_descriptors): + for f in additional_prl: + new_prl = LOOKUP_SEP.join([current_lookup, f]) + auto_lookups.append(new_prl) + done_queries[current_lookup] = obj_list + followed_descriptors.add(descriptor) else: # Either a singly related object that has already been fetched # (e.g. via select_related), or hopefully some other property @@ -1659,8 +1670,9 @@ def get_prefetcher(instance, attr): """ For the attribute 'attr' on the given instance, finds an object that has a get_prefetch_query_set(). - Return a 3 tuple containing: + Returns a 4 tuple containing: (the object with get_prefetch_query_set (or None), + the descriptor object representing this relationship (or None), a boolean that is False if the attribute was not found at all, a boolean that is True if the attribute has already been fetched) """ @@ -1694,7 +1706,7 @@ def get_prefetcher(instance, attr): rel_obj = getattr(instance, attr) if hasattr(rel_obj, 'get_prefetch_query_set'): prefetcher = rel_obj - return prefetcher, attr_found, is_fetched + return prefetcher, rel_obj_descriptor, attr_found, is_fetched def prefetch_one_level(instances, prefetcher, attname): |