diff --git a/django/db/models/query.py b/django/db/models/query.py
index 3342ef2086..ab4f3fc534 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -635,7 +635,7 @@ class QuerySet:
"arguments or 'get_latest_by' in the model's Meta."
)
- assert self.query.can_filter(), \
+ assert not self.query.is_sliced, \
"Cannot change a query once a slice has been taken."
obj = self._chain()
obj.query.set_limits(high=1)
@@ -664,7 +664,7 @@ class QuerySet:
Return a dictionary mapping each of the given IDs to the object with
that ID. If `id_list` isn't provided, evaluate the entire QuerySet.
"""
- assert self.query.can_filter(), \
+ assert not self.query.is_sliced, \
"Cannot use 'limit' or 'offset' with in_bulk"
if field_name != 'pk' and not self.model._meta.get_field(field_name).unique:
raise ValueError("in_bulk()'s field_name must be a unique field but %r isn't." % field_name)
@@ -689,7 +689,7 @@ class QuerySet:
def delete(self):
"""Delete the records in the current QuerySet."""
- assert self.query.can_filter(), \
+ assert not self.query.is_sliced, \
"Cannot use 'limit' or 'offset' with delete."
if self._fields is not None:
@@ -731,7 +731,7 @@ class QuerySet:
Update all elements in the current QuerySet, setting all the given
fields to the appropriate values.
"""
- assert self.query.can_filter(), \
+ assert not self.query.is_sliced, \
"Cannot update a query once a slice has been taken."
self._for_write = True
query = self.query.chain(sql.UpdateQuery)
@@ -751,7 +751,7 @@ class QuerySet:
code (it requires too much poking around at model internals to be
useful at that level).
"""
- assert self.query.can_filter(), \
+ assert not self.query.is_sliced, \
"Cannot update a query once a slice has been taken."
query = self.query.chain(sql.UpdateQuery)
query.add_update_fields(values)
@@ -903,7 +903,7 @@ class QuerySet:
def _filter_or_exclude(self, negate, *args, **kwargs):
if args or kwargs:
- assert self.query.can_filter(), \
+ assert not self.query.is_sliced, \
"Cannot filter a query once a slice has been taken."
clone = self._chain()
@@ -1072,7 +1072,7 @@ class QuerySet:
def order_by(self, *field_names):
"""Return a new QuerySet instance with the ordering changed."""
- assert self.query.can_filter(), \
+ assert not self.query.is_sliced, \
"Cannot reorder a query once a slice has been taken."
obj = self._chain()
obj.query.clear_ordering(force_empty=False)
@@ -1083,7 +1083,7 @@ class QuerySet:
"""
Return a new QuerySet instance that will select only distinct results.
"""
- assert self.query.can_filter(), \
+ assert not self.query.is_sliced, \
"Cannot create distinct fields once a slice has been taken."
obj = self._chain()
obj.query.add_distinct_fields(*field_names)
@@ -1093,7 +1093,7 @@ class QuerySet:
order_by=None, select_params=None):
"""Add extra SQL fragments to the query."""
self._not_support_combined_queries('extra')
- assert self.query.can_filter(), \
+ assert not self.query.is_sliced, \
"Cannot change a query once a slice has been taken"
clone = self._chain()
clone.query.add_extra(select, select_params, where, params, tables, order_by)
@@ -1101,7 +1101,7 @@ class QuerySet:
def reverse(self):
"""Reverse the ordering of the QuerySet."""
- if not self.query.can_filter():
+ if self.query.is_sliced:
raise TypeError('Cannot reverse a query once a slice has been taken.')
clone = self._chain()
clone.query.standard_ordering = not clone.query.standard_ordering
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index e15e64cde4..0369e01348 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -413,7 +413,6 @@ class Query(BaseExpression):
"""
if not self.annotation_select:
return {}
- has_limit = self.low_mark != 0 or self.high_mark is not None
existing_annotations = [
annotation for alias, annotation
in self.annotations.items()
@@ -430,7 +429,7 @@ class Query(BaseExpression):
# those operations must be done in a subquery so that the query
# aggregates on the limit and/or distinct results instead of applying
# the distinct and limit after the aggregation.
- if (isinstance(self.group_by, tuple) or has_limit or existing_annotations or
+ if (isinstance(self.group_by, tuple) or self.is_sliced or existing_annotations or
self.distinct or self.combinator):
from django.db.models.sql.subqueries import AggregateQuery
outer_query = AggregateQuery(self.model)
@@ -438,7 +437,7 @@ class Query(BaseExpression):
inner_query.select_for_update = False
inner_query.select_related = False
inner_query.set_annotation_mask(self.annotation_select)
- if not has_limit and not self.distinct_fields:
+ if not self.is_sliced and not self.distinct_fields:
# Queries with distinct_fields need ordering and when a limit
# is applied we must take the slice from the ordered query.
# Otherwise no need for ordering.
@@ -548,7 +547,7 @@ class Query(BaseExpression):
"""
assert self.model == rhs.model, \
"Cannot combine queries on two different base models."
- assert self.can_filter(), \
+ assert not self.is_sliced, \
"Cannot combine queries once a slice has been taken."
assert self.distinct == rhs.distinct, \
"Cannot combine a unique query with a non-unique query."
@@ -1762,6 +1761,10 @@ class Query(BaseExpression):
"""Clear any existing limits."""
self.low_mark, self.high_mark = 0, None
+ @property
+ def is_sliced(self):
+ return self.low_mark != 0 or self.high_mark is not None
+
def has_limit_one(self):
return self.high_mark is not None and (self.high_mark - self.low_mark) == 1
@@ -1771,7 +1774,7 @@ class Query(BaseExpression):
Typically, this means no limits or offsets have been put on the results.
"""
- return not self.low_mark and self.high_mark is None
+ return not self.is_sliced
def clear_select_clause(self):
"""Remove all fields from SELECT clause."""