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Fixed #17760 -- Implemented callable database features as cached prop…

…erties

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.
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commit aa423575e7b464433fcfc4bf4b8e1d7627b17ce6 1 parent 484fcd3
@claudep claudep authored
View
3  django/contrib/gis/db/backends/spatialite/creation.py
@@ -31,9 +31,6 @@ def create_test_db(self, verbosity=1, autoclobber=False):
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
31 django/db/backends/__init__.py
@@ -10,6 +10,7 @@
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 @@ def _supports_transactions(self):
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 StdDevPop(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
3  django/db/backends/creation.py
@@ -264,9 +264,6 @@ def create_test_db(self, verbosity=1, autoclobber=False):
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
32 django/db/backends/mysql/base.py
@@ -37,6 +37,7 @@
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
-
- def _can_introspect_foreign_keys(self):
+ 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]
+
+ @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
4 django/db/backends/sqlite3/base.py
@@ -19,6 +19,7 @@
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
3  tests/regressiontests/backends/tests.py
@@ -403,8 +403,7 @@ def test_database_operations_helper_class(self):
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
2  tests/regressiontests/transactions_regress/tests.py
@@ -208,7 +208,7 @@ def work():
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):
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