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