""" Query subclasses which provide extra functionality beyond simple data retrieval. """ from django.core.exceptions import FieldError from django.db import connections from django.db.models.query_utils import Q from django.db.models.sql.constants import ( CURSOR, GET_ITERATOR_CHUNK_SIZE, NO_RESULTS, ) from django.db.models.sql.query import Query __all__ = ['DeleteQuery', 'UpdateQuery', 'InsertQuery', 'AggregateQuery'] class DeleteQuery(Query): """A DELETE SQL query.""" compiler = 'SQLDeleteCompiler' def do_query(self, table, where, using): self.alias_map = {table: self.alias_map[table]} self.where = where cursor = self.get_compiler(using).execute_sql(CURSOR) return cursor.rowcount if cursor else 0 def delete_batch(self, pk_list, using): """ Set up and execute delete queries for all the objects in pk_list. More than one physical query may be executed if there are a lot of values in pk_list. """ # number of objects deleted num_deleted = 0 field = self.get_meta().pk for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE): self.where = self.where_class() self.add_q(Q( **{field.attname + '__in': pk_list[offset:offset + GET_ITERATOR_CHUNK_SIZE]})) num_deleted += self.do_query(self.get_meta().db_table, self.where, using=using) return num_deleted def delete_qs(self, query, using): """ Delete the queryset in one SQL query (if possible). For simple queries this is done by copying the query.query.where to self.query, for complex queries by using subquery. """ innerq = query.query # Make sure the inner query has at least one table in use. innerq.get_initial_alias() # The same for our new query. self.get_initial_alias() innerq_used_tables = tuple([t for t in innerq.alias_map if innerq.alias_refcount[t]]) if not innerq_used_tables or innerq_used_tables == tuple(self.alias_map): # There is only the base table in use in the query. self.where = innerq.where else: pk = query.model._meta.pk if not connections[using].features.update_can_self_select: # We can't do the delete using subquery. values = list(query.values_list('pk', flat=True)) if not values: return 0 return self.delete_batch(values, using) else: innerq.clear_select_clause() innerq.select = [ pk.get_col(self.get_initial_alias()) ] values = innerq self.where = self.where_class() self.add_q(Q(pk__in=values)) cursor = self.get_compiler(using).execute_sql(CURSOR) return cursor.rowcount if cursor else 0 class UpdateQuery(Query): """An UPDATE SQL query.""" compiler = 'SQLUpdateCompiler' def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) self._setup_query() def _setup_query(self): """ Run on initialization and after cloning. Any attributes that would normally be set in __init__ should go in here, instead, so that they are also set up after a clone() call. """ self.values = [] self.related_ids = None self.related_updates = {} def clone(self, klass=None, **kwargs): return super().clone(klass, related_updates=self.related_updates.copy(), **kwargs) def update_batch(self, pk_list, values, using): self.add_update_values(values) for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE): self.where = self.where_class() self.add_q(Q(pk__in=pk_list[offset: offset + GET_ITERATOR_CHUNK_SIZE])) self.get_compiler(using).execute_sql(NO_RESULTS) def add_update_values(self, values): """ Convert a dictionary of field name to value mappings into an update query. This is the entry point for the public update() method on querysets. """ values_seq = [] for name, val in values.items(): field = self.get_meta().get_field(name) direct = not (field.auto_created and not field.concrete) or not field.concrete model = field.model._meta.concrete_model if not direct or (field.is_relation and field.many_to_many): raise FieldError( 'Cannot update model field %r (only non-relations and ' 'foreign keys permitted).' % field ) if model is not self.get_meta().model: self.add_related_update(model, field, val) continue values_seq.append((field, model, val)) return self.add_update_fields(values_seq) def add_update_fields(self, values_seq): """ Append a sequence of (field, model, value) triples to the internal list that will be used to generate the UPDATE query. Might be more usefully called add_update_targets() to hint at the extra information here. """ for field, model, val in values_seq: if hasattr(val, 'resolve_expression'): # Resolve expressions here so that annotations are no longer needed val = val.resolve_expression(self, allow_joins=False, for_save=True) self.values.append((field, model, val)) def add_related_update(self, model, field, value): """ Add (name, value) to an update query for an ancestor model. Update are coalesced so that only one update query per ancestor is run. """ self.related_updates.setdefault(model, []).append((field, None, value)) def get_related_updates(self): """ Return a list of query objects: one for each update required to an ancestor model. Each query will have the same filtering conditions as the current query but will only update a single table. """ if not self.related_updates: return [] result = [] for model, values in self.related_updates.items(): query = UpdateQuery(model) query.values = values if self.related_ids is not None: query.add_filter(('pk__in', self.related_ids)) result.append(query) return result class InsertQuery(Query): compiler = 'SQLInsertCompiler' def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) self.fields = [] self.objs = [] def insert_values(self, fields, objs, raw=False): self.fields = fields self.objs = objs self.raw = raw class AggregateQuery(Query): """ Take another query as a parameter to the FROM clause and only select the elements in the provided list. """ compiler = 'SQLAggregateCompiler' def add_subquery(self, query, using): query.subquery = True self.subquery, self.sub_params = query.get_compiler(using).as_sql(with_col_aliases=True)