django1/django/db/backends/sqlite3/features.py

59 lines
2.2 KiB
Python

import sys
from django.db import utils
from django.db.backends.base.features import BaseDatabaseFeatures
from django.utils.functional import cached_property
from .base import Database
class DatabaseFeatures(BaseDatabaseFeatures):
# SQLite can read from a cursor since SQLite 3.6.5, subject to the caveat
# that statements within a connection aren't isolated from each other. See
# https://sqlite.org/isolation.html.
can_use_chunked_reads = True
test_db_allows_multiple_connections = False
supports_unspecified_pk = True
supports_timezones = False
max_query_params = 999
supports_mixed_date_datetime_comparisons = False
autocommits_when_autocommit_is_off = sys.version_info < (3, 6)
can_introspect_decimal_field = False
can_introspect_duration_field = False
can_introspect_positive_integer_field = True
can_introspect_small_integer_field = True
supports_transactions = True
atomic_transactions = False
can_rollback_ddl = True
supports_atomic_references_rename = False
supports_paramstyle_pyformat = False
supports_sequence_reset = False
can_clone_databases = True
supports_temporal_subtraction = True
ignores_table_name_case = True
supports_cast_with_precision = False
time_cast_precision = 3
can_release_savepoints = True
supports_partial_indexes = Database.version_info >= (3, 8, 0)
# Is "ALTER TABLE ... RENAME COLUMN" supported?
can_alter_table_rename_column = Database.sqlite_version_info >= (3, 25, 0)
@cached_property
def supports_stddev(self):
"""
Confirm support for STDDEV and related stats functions.
SQLite supports STDDEV as an extension package; so
connection.ops.check_expression_support() can't unilaterally
rule out support for STDDEV. Manually check whether the call works.
"""
with self.connection.cursor() as cursor:
cursor.execute('CREATE TABLE STDDEV_TEST (X INT)')
try:
cursor.execute('SELECT STDDEV(*) FROM STDDEV_TEST')
has_support = True
except utils.DatabaseError:
has_support = False
cursor.execute('DROP TABLE STDDEV_TEST')
return has_support