Fixed #17760 -- Implemented callable database features as cached properties

This does remove the requirement to call features.confirm() method
before checking the properties.
Thanks cdestiger and Ramiro Morales for their work on the patch.
This commit is contained in:
Claude Paroz 2012-06-09 15:59:52 +02:00
parent 484fcd34a4
commit aa423575e7
7 changed files with 29 additions and 47 deletions

View File

@ -31,9 +31,6 @@ class SpatiaLiteCreation(DatabaseCreation):
self.connection.close()
self.connection.settings_dict["NAME"] = test_database_name
# Confirm the feature set of the test database
self.connection.features.confirm()
# Need to load the SpatiaLite initialization SQL before running `syncdb`.
self.load_spatialite_sql()

View File

@ -10,6 +10,7 @@ from django.conf import settings
from django.db import DEFAULT_DB_ALIAS
from django.db.backends import util
from django.db.transaction import TransactionManagementError
from django.utils.functional import cached_property
from django.utils.importlib import import_module
from django.utils.timezone import is_aware
@ -402,12 +403,10 @@ class BaseDatabaseFeatures(object):
# Does the backend reset sequences between tests?
supports_sequence_reset = True
# Features that need to be confirmed at runtime
# Cache whether the confirmation has been performed.
_confirmed = False
supports_transactions = None
supports_stddev = None
can_introspect_foreign_keys = None
# Confirm support for introspected foreign keys
# Every database can do this reliably, except MySQL,
# which can't do it for MyISAM tables
can_introspect_foreign_keys = True
# Support for the DISTINCT ON clause
can_distinct_on_fields = False
@ -415,15 +414,8 @@ class BaseDatabaseFeatures(object):
def __init__(self, connection):
self.connection = connection
def confirm(self):
"Perform manual checks of any database features that might vary between installs"
if not self._confirmed:
self._confirmed = True
self.supports_transactions = self._supports_transactions()
self.supports_stddev = self._supports_stddev()
self.can_introspect_foreign_keys = self._can_introspect_foreign_keys()
def _supports_transactions(self):
@cached_property
def supports_transactions(self):
"Confirm support for transactions"
cursor = self.connection.cursor()
cursor.execute('CREATE TABLE ROLLBACK_TEST (X INT)')
@ -436,7 +428,8 @@ class BaseDatabaseFeatures(object):
self.connection._commit()
return count == 0
def _supports_stddev(self):
@cached_property
def supports_stddev(self):
"Confirm support for STDDEV and related stats functions"
class StdDevPop(object):
sql_function = 'STDDEV_POP'
@ -447,12 +440,6 @@ class BaseDatabaseFeatures(object):
except NotImplementedError:
return False
def _can_introspect_foreign_keys(self):
"Confirm support for introspected foreign keys"
# Every database can do this reliably, except MySQL,
# which can't do it for MyISAM tables
return True
class BaseDatabaseOperations(object):
"""

View File

@ -264,9 +264,6 @@ class BaseDatabaseCreation(object):
self.connection.close()
self.connection.settings_dict["NAME"] = test_database_name
# Confirm the feature set of the test database
self.connection.features.confirm()
# Report syncdb messages at one level lower than that requested.
# This ensures we don't get flooded with messages during testing
# (unless you really ask to be flooded)

View File

@ -37,6 +37,7 @@ from django.db.backends.mysql.client import DatabaseClient
from django.db.backends.mysql.creation import DatabaseCreation
from django.db.backends.mysql.introspection import DatabaseIntrospection
from django.db.backends.mysql.validation import DatabaseValidation
from django.utils.functional import cached_property
from django.utils.safestring import SafeString, SafeUnicode
from django.utils import timezone
@ -170,26 +171,25 @@ class DatabaseFeatures(BaseDatabaseFeatures):
def __init__(self, connection):
super(DatabaseFeatures, self).__init__(connection)
self._storage_engine = None
@cached_property
def _mysql_storage_engine(self):
"Internal method used in Django tests. Don't rely on this from your code"
if self._storage_engine is None:
cursor = self.connection.cursor()
cursor.execute('CREATE TABLE INTROSPECT_TEST (X INT)')
# This command is MySQL specific; the second column
# will tell you the default table type of the created
# table. Since all Django's test tables will have the same
# table type, that's enough to evaluate the feature.
cursor.execute("SHOW TABLE STATUS WHERE Name='INTROSPECT_TEST'")
result = cursor.fetchone()
cursor.execute('DROP TABLE INTROSPECT_TEST')
self._storage_engine = result[1]
return self._storage_engine
cursor = self.connection.cursor()
cursor.execute('CREATE TABLE INTROSPECT_TEST (X INT)')
# This command is MySQL specific; the second column
# will tell you the default table type of the created
# table. Since all Django's test tables will have the same
# table type, that's enough to evaluate the feature.
cursor.execute("SHOW TABLE STATUS WHERE Name='INTROSPECT_TEST'")
result = cursor.fetchone()
cursor.execute('DROP TABLE INTROSPECT_TEST')
return result[1]
def _can_introspect_foreign_keys(self):
@cached_property
def can_introspect_foreign_keys(self):
"Confirm support for introspected foreign keys"
return self._mysql_storage_engine() != 'MyISAM'
return self._mysql_storage_engine != 'MyISAM'
class DatabaseOperations(BaseDatabaseOperations):
compiler_module = "django.db.backends.mysql.compiler"

View File

@ -19,6 +19,7 @@ from django.db.backends.sqlite3.client import DatabaseClient
from django.db.backends.sqlite3.creation import DatabaseCreation
from django.db.backends.sqlite3.introspection import DatabaseIntrospection
from django.utils.dateparse import parse_date, parse_datetime, parse_time
from django.utils.functional import cached_property
from django.utils.safestring import SafeString
from django.utils import timezone
@ -86,7 +87,8 @@ class DatabaseFeatures(BaseDatabaseFeatures):
has_bulk_insert = True
can_combine_inserts_with_and_without_auto_increment_pk = True
def _supports_stddev(self):
@cached_property
def supports_stddev(self):
"""Confirm support for STDDEV and related stats functions
SQLite supports STDDEV as an extension package; so

View File

@ -403,8 +403,7 @@ class BackendTestCase(TestCase):
self.assertTrue(hasattr(connection.ops, 'connection'))
self.assertEqual(connection, connection.ops.connection)
def test_supports_needed_confirm(self):
connection.features.confirm()
def test_cached_db_features(self):
self.assertIn(connection.features.supports_transactions, (True, False))
self.assertIn(connection.features.supports_stddev, (True, False))
self.assertIn(connection.features.can_introspect_foreign_keys, (True, False))

View File

@ -208,7 +208,7 @@ class SavepointTest(TransactionTestCase):
work()
@skipIf(connection.vendor == 'mysql' and \
connection.features._mysql_storage_engine() == 'MyISAM',
connection.features._mysql_storage_engine == 'MyISAM',
"MyISAM MySQL storage engine doesn't support savepoints")
@skipUnlessDBFeature('uses_savepoints')
def test_savepoint_rollback(self):