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