app/django/db/models/sql/subqueries.py
author Pawel Solyga <Pawel.Solyga@gmail.com>
Tue, 14 Oct 2008 16:00:59 +0000
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Load ../vendor/django into trunk/app/django.
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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.models.sql.constants import *
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from django.db.models.sql.datastructures import Date
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from django.db.models.sql.query import Query
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from django.db.models.sql.where import AND
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__all__ = ['DeleteQuery', 'UpdateQuery', 'InsertQuery', 'DateQuery',
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        'CountQuery']
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class DeleteQuery(Query):
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    """
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    Delete queries are done through this class, since they are more constrained
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    than general queries.
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    """
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    def as_sql(self):
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        """
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        Creates the SQL for this query. Returns the SQL string and list of
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        parameters.
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        """
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        assert len(self.tables) == 1, \
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                "Can only delete from one table at a time."
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        result = ['DELETE FROM %s' % self.quote_name_unless_alias(self.tables[0])]
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        where, params = self.where.as_sql()
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        result.append('WHERE %s' % where)
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        return ' '.join(result), tuple(params)
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    def do_query(self, table, where):
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        self.tables = [table]
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        self.where = where
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        self.execute_sql(None)
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    def delete_batch_related(self, pk_list):
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        """
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        Set up and execute delete queries for all the objects related to the
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        primary key values in pk_list. To delete the objects themselves, use
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        the delete_batch() method.
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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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        from django.contrib.contenttypes import generic
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        cls = self.model
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        for related in cls._meta.get_all_related_many_to_many_objects():
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            if not isinstance(related.field, generic.GenericRelation):
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                for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
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                    where = self.where_class()
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                    where.add((None, related.field.m2m_reverse_name(),
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                            related.field, 'in',
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                            pk_list[offset : offset+GET_ITERATOR_CHUNK_SIZE]),
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                            AND)
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                    self.do_query(related.field.m2m_db_table(), where)
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        for f in cls._meta.many_to_many:
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            w1 = self.where_class()
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            if isinstance(f, generic.GenericRelation):
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                from django.contrib.contenttypes.models import ContentType
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                field = f.rel.to._meta.get_field(f.content_type_field_name)
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                w1.add((None, field.column, field, 'exact',
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                        ContentType.objects.get_for_model(cls).id), AND)
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            for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
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                where = self.where_class()
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                where.add((None, f.m2m_column_name(), f, 'in',
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                        pk_list[offset : offset + GET_ITERATOR_CHUNK_SIZE]),
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                        AND)
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                if w1:
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                    where.add(w1, AND)
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                self.do_query(f.m2m_db_table(), where)
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    def delete_batch(self, pk_list):
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        """
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        Set up and execute delete queries for all the objects in pk_list. This
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        should be called after delete_batch_related(), if necessary.
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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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        for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
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            where = self.where_class()
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            field = self.model._meta.pk
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            where.add((None, field.column, field, 'in',
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                    pk_list[offset : offset + GET_ITERATOR_CHUNK_SIZE]), AND)
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            self.do_query(self.model._meta.db_table, where)
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class UpdateQuery(Query):
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    """
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    Represents an "update" SQL query.
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    """
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    def __init__(self, *args, **kwargs):
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        super(UpdateQuery, self).__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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        Runs on initialization and after cloning. Any attributes that would
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        normally be set in __init__ should go in here, instead, so that they
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        are also set up after a clone() call.
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        """
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        self.values = []
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        self.related_ids = None
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        if not hasattr(self, 'related_updates'):
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            self.related_updates = {}
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    def clone(self, klass=None, **kwargs):
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        return super(UpdateQuery, self).clone(klass,
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                related_updates=self.related_updates.copy(), **kwargs)
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    def execute_sql(self, result_type=None):
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        """
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        Execute the specified update. Returns the number of rows affected by
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        the primary update query (there could be other updates on related
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        tables, but their rowcounts are not returned).
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        """
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        cursor = super(UpdateQuery, self).execute_sql(result_type)
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        rows = cursor.rowcount
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        del cursor
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        for query in self.get_related_updates():
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            query.execute_sql(result_type)
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        return rows
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    def as_sql(self):
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        """
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        Creates the SQL for this query. Returns the SQL string and list of
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        parameters.
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        """
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        self.pre_sql_setup()
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        if not self.values:
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            return '', ()
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        table = self.tables[0]
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        qn = self.quote_name_unless_alias
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        result = ['UPDATE %s' % qn(table)]
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        result.append('SET')
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        values, update_params = [], []
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        for name, val, placeholder in self.values:
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            if val is not None:
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                values.append('%s = %s' % (qn(name), placeholder))
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                update_params.append(val)
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            else:
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                values.append('%s = NULL' % qn(name))
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        result.append(', '.join(values))
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        where, params = self.where.as_sql()
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        if where:
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            result.append('WHERE %s' % where)
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        return ' '.join(result), tuple(update_params + params)
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    def pre_sql_setup(self):
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        """
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        If the update depends on results from other tables, we need to do some
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        munging of the "where" conditions to match the format required for
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        (portable) SQL updates. That is done here.
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        Further, if we are going to be running multiple updates, we pull out
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        the id values to update at this point so that they don't change as a
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        result of the progressive updates.
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        """
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        self.select_related = False
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        self.clear_ordering(True)
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        super(UpdateQuery, self).pre_sql_setup()
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        count = self.count_active_tables()
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        if not self.related_updates and count == 1:
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            return
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        # We need to use a sub-select in the where clause to filter on things
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        # from other tables.
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        query = self.clone(klass=Query)
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        query.bump_prefix()
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        query.extra_select = {}
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        first_table = query.tables[0]
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        if query.alias_refcount[first_table] == 1:
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            # We can remove one table from the inner query.
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            query.unref_alias(first_table)
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            for i in xrange(1, len(query.tables)):
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                table = query.tables[i]
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                if query.alias_refcount[table]:
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                    break
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            join_info = query.alias_map[table]
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            query.select = [(join_info[RHS_ALIAS], join_info[RHS_JOIN_COL])]
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            must_pre_select = False
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        else:
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            query.select = []
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            query.add_fields([query.model._meta.pk.name])
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            must_pre_select = not self.connection.features.update_can_self_select
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        # Now we adjust the current query: reset the where clause and get rid
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        # of all the tables we don't need (since they're in the sub-select).
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        self.where = self.where_class()
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        if self.related_updates or must_pre_select:
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            # Either we're using the idents in multiple update queries (so
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            # don't want them to change), or the db backend doesn't support
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            # selecting from the updating table (e.g. MySQL).
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            idents = []
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            for rows in query.execute_sql(MULTI):
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                idents.extend([r[0] for r in rows])
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            self.add_filter(('pk__in', idents))
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            self.related_ids = idents
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        else:
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            # The fast path. Filters and updates in one query.
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            self.add_filter(('pk__in', query))
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        for alias in self.tables[1:]:
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            self.alias_refcount[alias] = 0
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    def clear_related(self, related_field, pk_list):
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        """
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        Set up and execute an update query that clears related entries for the
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        keys in pk_list.
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        This is used by the QuerySet.delete_objects() method.
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        """
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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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            f = self.model._meta.pk
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            self.where.add((None, f.column, f, 'in',
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                    pk_list[offset : offset + GET_ITERATOR_CHUNK_SIZE]),
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                    AND)
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            self.values = [(related_field.column, None, '%s')]
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            self.execute_sql(None)
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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.iteritems():
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            field, model, direct, m2m = self.model._meta.get_field_by_name(name)
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            if not direct or m2m:
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                raise FieldError('Cannot update model field %r (only non-relations and foreign keys permitted).' % field)
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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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        Turn a sequence of (field, model, value) triples into an update query.
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        Used by add_update_values() as well as the "fast" update path when
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        saving models.
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        """
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        from django.db.models.base import Model
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        for field, model, val in values_seq:
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            # FIXME: Some sort of db_prep_* is probably more appropriate here.
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            if field.rel and isinstance(val, Model):
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                val = val.pk
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            # Getting the placeholder for the field.
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            if hasattr(field, 'get_placeholder'):
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                placeholder = field.get_placeholder(val)
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            else:
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                placeholder = '%s'
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            if model:
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                self.add_related_update(model, field.column, val, placeholder)
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            else:
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                self.values.append((field.column, val, placeholder))
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    def add_related_update(self, model, column, value, placeholder):
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        """
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        Adds (name, value) to an update query for an ancestor model.
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        Updates are coalesced so that we only run one update query per ancestor.
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        """
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        try:
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            self.related_updates[model].append((column, value, placeholder))
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        except KeyError:
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            self.related_updates[model] = [(column, value, placeholder)]
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    def get_related_updates(self):
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        """
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        Returns 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.iteritems():
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            query = UpdateQuery(model, self.connection)
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            query.values = values
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            if self.related_ids:
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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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    def __init__(self, *args, **kwargs):
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        super(InsertQuery, self).__init__(*args, **kwargs)
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        self.columns = []
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        self.values = []
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        self.params = ()
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    def clone(self, klass=None, **kwargs):
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        extras = {'columns': self.columns[:], 'values': self.values[:],
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                'params': self.params}
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        extras.update(kwargs)
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        return super(InsertQuery, self).clone(klass, **extras)
54
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    def as_sql(self):
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        # We don't need quote_name_unless_alias() here, since these are all
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        # going to be column names (so we can avoid the extra overhead).
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        qn = self.connection.ops.quote_name
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        result = ['INSERT INTO %s' % qn(self.model._meta.db_table)]
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        result.append('(%s)' % ', '.join([qn(c) for c in self.columns]))
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        result.append('VALUES (%s)' % ', '.join(self.values))
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        return ' '.join(result), self.params
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    def execute_sql(self, return_id=False):
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        cursor = super(InsertQuery, self).execute_sql(None)
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        if return_id:
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            return self.connection.ops.last_insert_id(cursor,
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                    self.model._meta.db_table, self.model._meta.pk.column)
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    def insert_values(self, insert_values, raw_values=False):
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        """
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        Set up the insert query from the 'insert_values' dictionary. The
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        dictionary gives the model field names and their target values.
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        If 'raw_values' is True, the values in the 'insert_values' dictionary
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        are inserted directly into the query, rather than passed as SQL
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        parameters. This provides a way to insert NULL and DEFAULT keywords
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        into the query, for example.
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        """
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        placeholders, values = [], []
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        for field, val in insert_values:
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            if hasattr(field, 'get_placeholder'):
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                # Some fields (e.g. geo fields) need special munging before
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                # they can be inserted.
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                placeholders.append(field.get_placeholder(val))
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            else:
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                placeholders.append('%s')
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            self.columns.append(field.column)
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            values.append(val)
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        if raw_values:
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            self.values.extend(values)
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        else:
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            self.params += tuple(values)
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            self.values.extend(placeholders)
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class DateQuery(Query):
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    """
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    A DateQuery is a normal query, except that it specifically selects a single
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    date field. This requires some special handling when converting the results
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    back to Python objects, so we put it in a separate class.
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    """
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    def __getstate__(self):
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        """
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        Special DateQuery-specific pickle handling.
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        """
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        for elt in self.select:
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            if isinstance(elt, Date):
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                # Eliminate a method reference that can't be pickled. The
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                # __setstate__ method restores this.
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                elt.date_sql_func = None
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        return super(DateQuery, self).__getstate__()
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    def __setstate__(self, obj_dict):
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        super(DateQuery, self).__setstate__(obj_dict)
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        for elt in self.select:
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            if isinstance(elt, Date):
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                self.date_sql_func = self.connection.ops.date_trunc_sql
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54
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    def results_iter(self):
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        """
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        Returns an iterator over the results from executing this query.
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        """
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        resolve_columns = hasattr(self, 'resolve_columns')
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        if resolve_columns:
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            from django.db.models.fields import DateTimeField
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            fields = [DateTimeField()]
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        else:
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            from django.db.backends.util import typecast_timestamp
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            needs_string_cast = self.connection.features.needs_datetime_string_cast
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        offset = len(self.extra_select)
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        for rows in self.execute_sql(MULTI):
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            for row in rows:
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                date = row[offset]
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   380
                if resolve_columns:
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                    date = self.resolve_columns(row, fields)[offset]
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                elif needs_string_cast:
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                    date = typecast_timestamp(str(date))
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                yield date
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   386
    def add_date_select(self, field, lookup_type, order='ASC'):
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        """
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        Converts the query into a date extraction query.
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   389
        """
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        result = self.setup_joins([field.name], self.get_meta(),
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   391
                self.get_initial_alias(), False)
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        alias = result[3][-1]
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   393
        select = Date((alias, field.column), lookup_type,
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   394
                self.connection.ops.date_trunc_sql)
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   395
        self.select = [select]
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        self.select_fields = [None]
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        self.select_related = False # See #7097.
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   398
        self.extra_select = {}
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   399
        self.distinct = True
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   400
        self.order_by = order == 'ASC' and [1] or [-1]
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   401
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   402
class CountQuery(Query):
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    """
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    A CountQuery knows how to take a normal query which would select over
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   405
    multiple distinct columns and turn it into SQL that can be used on a
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   406
    variety of backends (it requires a select in the FROM clause).
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   407
    """
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   408
    def get_from_clause(self):
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   409
        result, params = self._query.as_sql()
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   410
        return ['(%s) A1' % result], params
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   411
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    def get_ordering(self):
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        return ()