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- from django.db import utils
- from django.db.backends.base.features import BaseDatabaseFeatures
- from django.utils.functional import cached_property
-
-
- class DatabaseFeatures(BaseDatabaseFeatures):
- # SQLite cannot handle us only partially reading from a cursor's result set
- # and then writing the same rows to the database in another cursor. This
- # setting ensures we always read result sets fully into memory all in one
- # go.
- can_use_chunked_reads = False
- test_db_allows_multiple_connections = False
- supports_unspecified_pk = True
- supports_timezones = False
- max_query_params = 999
- supports_mixed_date_datetime_comparisons = False
- supports_column_check_constraints = False
- autocommits_when_autocommit_is_off = True
- can_introspect_decimal_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
- uses_savepoints = True
- can_release_savepoints = True
-
- @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
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