Source code for django.db.models.query_utils

Various data structures used in query construction.

Factored out from django.db.models.query to avoid making the main module very
large and/or so that they can be used by other modules without getting into
circular import difficulties.
import copy
import functools
import inspect
import warnings
from collections import namedtuple

from django.core.exceptions import FieldDoesNotExist, FieldError
from django.db.models.constants import LOOKUP_SEP
from django.utils import tree
from django.utils.deprecation import RemovedInDjango40Warning

# PathInfo is used when converting lookups (fk__somecol). The contents
# describe the relation in Model terms (model Options and Fields for both
# sides of the relation. The join_field is the field backing the relation.
PathInfo = namedtuple('PathInfo', 'from_opts to_opts target_fields join_field m2m direct filtered_relation')

class InvalidQueryType(type):
    def _subclasses(self):
        return (FieldDoesNotExist, FieldError)

    def __warn(self):
            'The InvalidQuery exception class is deprecated. Use '
            'FieldDoesNotExist or FieldError instead.',

    def __instancecheck__(self, instance):
        return isinstance(instance, self._subclasses) or super().__instancecheck__(instance)

    def __subclasscheck__(self, subclass):
        return issubclass(subclass, self._subclasses) or super().__subclasscheck__(subclass)

class InvalidQuery(Exception, metaclass=InvalidQueryType):

def subclasses(cls):
    yield cls
    for subclass in cls.__subclasses__():
        yield from subclasses(subclass)

[docs]class Q(tree.Node): """ Encapsulate filters as objects that can then be combined logically (using `&` and `|`). """ # Connection types AND = 'AND' OR = 'OR' default = AND conditional = True def __init__(self, *args, _connector=None, _negated=False, **kwargs): super().__init__(children=[*args, *sorted(kwargs.items())], connector=_connector, negated=_negated) def _combine(self, other, conn): if not(isinstance(other, Q) or getattr(other, 'conditional', False) is True): raise TypeError(other) if not self: return other.copy() if hasattr(other, 'copy') else copy.copy(other) elif isinstance(other, Q) and not other: _, args, kwargs = self.deconstruct() return type(self)(*args, **kwargs) obj = type(self)() obj.connector = conn obj.add(self, conn) obj.add(other, conn) return obj def __or__(self, other): return self._combine(other, self.OR) def __and__(self, other): return self._combine(other, self.AND) def __invert__(self): obj = type(self)() obj.add(self, self.AND) obj.negate() return obj def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False): # We must promote any new joins to left outer joins so that when Q is # used as an expression, rows aren't filtered due to joins. clause, joins = query._add_q( self, reuse, allow_joins=allow_joins, split_subq=False, check_filterable=False, ) query.promote_joins(joins) return clause def deconstruct(self): path = '%s.%s' % (self.__class__.__module__, self.__class__.__name__) if path.startswith('django.db.models.query_utils'): path = path.replace('django.db.models.query_utils', 'django.db.models') args = tuple(self.children) kwargs = {} if self.connector != self.default: kwargs['_connector'] = self.connector if self.negated: kwargs['_negated'] = True return path, args, kwargs
class DeferredAttribute: """ A wrapper for a deferred-loading field. When the value is read from this object the first time, the query is executed. """ def __init__(self, field): self.field = field def __get__(self, instance, cls=None): """ Retrieve and caches the value from the datastore on the first lookup. Return the cached value. """ if instance is None: return self data = instance.__dict__ field_name = self.field.attname if field_name not in data: # Let's see if the field is part of the parent chain. If so we # might be able to reuse the already loaded value. Refs #18343. val = self._check_parent_chain(instance) if val is None: instance.refresh_from_db(fields=[field_name]) else: data[field_name] = val return data[field_name] def _check_parent_chain(self, instance): """ Check if the field value can be fetched from a parent field already loaded in the instance. This can be done if the to-be fetched field is a primary key field. """ opts = instance._meta link_field = opts.get_ancestor_link(self.field.model) if self.field.primary_key and self.field != link_field: return getattr(instance, link_field.attname) return None class RegisterLookupMixin: @classmethod def _get_lookup(cls, lookup_name): return cls.get_lookups().get(lookup_name, None) @classmethod @functools.lru_cache(maxsize=None) def get_lookups(cls): class_lookups = [parent.__dict__.get('class_lookups', {}) for parent in inspect.getmro(cls)] return cls.merge_dicts(class_lookups) def get_lookup(self, lookup_name): from django.db.models.lookups import Lookup found = self._get_lookup(lookup_name) if found is None and hasattr(self, 'output_field'): return self.output_field.get_lookup(lookup_name) if found is not None and not issubclass(found, Lookup): return None return found def get_transform(self, lookup_name): from django.db.models.lookups import Transform found = self._get_lookup(lookup_name) if found is None and hasattr(self, 'output_field'): return self.output_field.get_transform(lookup_name) if found is not None and not issubclass(found, Transform): return None return found @staticmethod def merge_dicts(dicts): """ Merge dicts in reverse to preference the order of the original list. e.g., merge_dicts([a, b]) will preference the keys in 'a' over those in 'b'. """ merged = {} for d in reversed(dicts): merged.update(d) return merged @classmethod def _clear_cached_lookups(cls): for subclass in subclasses(cls): subclass.get_lookups.cache_clear() @classmethod def register_lookup(cls, lookup, lookup_name=None): if lookup_name is None: lookup_name = lookup.lookup_name if 'class_lookups' not in cls.__dict__: cls.class_lookups = {} cls.class_lookups[lookup_name] = lookup cls._clear_cached_lookups() return lookup @classmethod def _unregister_lookup(cls, lookup, lookup_name=None): """ Remove given lookup from cls lookups. For use in tests only as it's not thread-safe. """ if lookup_name is None: lookup_name = lookup.lookup_name del cls.class_lookups[lookup_name] def select_related_descend(field, restricted, requested, load_fields, reverse=False): """ Return True if this field should be used to descend deeper for select_related() purposes. Used by both the query construction code (sql.query.fill_related_selections()) and the model instance creation code (query.get_klass_info()). Arguments: * field - the field to be checked * restricted - a boolean field, indicating if the field list has been manually restricted using a requested clause) * requested - The select_related() dictionary. * load_fields - the set of fields to be loaded on this model * reverse - boolean, True if we are checking a reverse select related """ if not field.remote_field: return False if field.remote_field.parent_link and not reverse: return False if restricted: if reverse and field.related_query_name() not in requested: return False if not reverse and not in requested: return False if not restricted and field.null: return False if load_fields: if field.attname not in load_fields: if restricted and in requested: msg = ( 'Field %s.%s cannot be both deferred and traversed using ' 'select_related at the same time.' ) % (field.model._meta.object_name, raise FieldError(msg) return True def refs_expression(lookup_parts, annotations): """ Check if the lookup_parts contains references to the given annotations set. Because the LOOKUP_SEP is contained in the default annotation names, check each prefix of the lookup_parts for a match. """ for n in range(1, len(lookup_parts) + 1): level_n_lookup = LOOKUP_SEP.join(lookup_parts[0:n]) if level_n_lookup in annotations and annotations[level_n_lookup]: return annotations[level_n_lookup], lookup_parts[n:] return False, () def check_rel_lookup_compatibility(model, target_opts, field): """ Check that self.model is compatible with target_opts. Compatibility is OK if: 1) model and opts match (where proxy inheritance is removed) 2) model is parent of opts' model or the other way around """ def check(opts): return ( model._meta.concrete_model == opts.concrete_model or opts.concrete_model in model._meta.get_parent_list() or model in opts.get_parent_list() ) # If the field is a primary key, then doing a query against the field's # model is ok, too. Consider the case: # class Restaurant(models.Model): # place = OneToOneField(Place, primary_key=True): # Restaurant.objects.filter(pk__in=Restaurant.objects.all()). # If we didn't have the primary key check, then pk__in (== place__in) would # give Place's opts as the target opts, but Restaurant isn't compatible # with that. This logic applies only to primary keys, as when doing __in=qs, # we are going to turn this into __in=qs.values('pk') later on. return ( check(target_opts) or (getattr(field, 'primary_key', False) and check(field.model._meta)) )
[docs]class FilteredRelation: """Specify custom filtering in the ON clause of SQL joins.""" def __init__(self, relation_name, *, condition=Q()): if not relation_name: raise ValueError('relation_name cannot be empty.') self.relation_name = relation_name self.alias = None if not isinstance(condition, Q): raise ValueError('condition argument must be a Q() instance.') self.condition = condition self.path = [] def __eq__(self, other): if not isinstance(other, self.__class__): return NotImplemented return ( self.relation_name == other.relation_name and self.alias == other.alias and self.condition == other.condition ) def clone(self): clone = FilteredRelation(self.relation_name, condition=self.condition) clone.alias = self.alias clone.path = self.path[:] return clone def resolve_expression(self, *args, **kwargs): """ QuerySet.annotate() only accepts expression-like arguments (with a resolve_expression() method). """ raise NotImplementedError('FilteredRelation.resolve_expression() is unused.') def as_sql(self, compiler, connection): # Resolve the condition in Join.filtered_relation. query = compiler.query where = query.build_filtered_relation_q(self.condition, reuse=set(self.path)) return compiler.compile(where)
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