Ensure cursors are closed when no longer needed.

This commit touchs various parts of the code base and test framework. Any
found usage of opening a cursor for the sake of initializing a connection
has been replaced with 'ensure_connection()'.

django/contrib/gis/db/backends/postgis/creation.py

@@ -11,7 +11,7 @@ class PostGISCreation(DatabaseCreation):
     @cached_property
     def template_postgis(self):
         template_postgis = getattr(settings, 'POSTGIS_TEMPLATE', 'template_postgis')
-        cursor = self.connection.cursor()
+        with self.connection.cursor() as cursor:
             cursor.execute('SELECT 1 FROM pg_database WHERE datname = %s LIMIT 1;', (template_postgis,))
             if cursor.fetchone():
                 return template_postgis
@@ -88,7 +88,7 @@ class PostGISCreation(DatabaseCreation):
             # Connect to the test database in order to create the postgis extension
             self.connection.close()
             self.connection.settings_dict["NAME"] = test_database_name
-            cursor = self.connection.cursor()
+            with self.connection.cursor() as cursor:
                 cursor.execute("CREATE EXTENSION IF NOT EXISTS postgis")
                 cursor.connection.commit()
 

django/contrib/gis/db/backends/spatialite/creation.py

@@ -55,9 +55,8 @@ class SpatiaLiteCreation(DatabaseCreation):
 
         call_command('createcachetable', database=self.connection.alias)
 
-        # Get a cursor (even though we don't need one yet). This has
+        # Ensure a connection for the side effect of initializing the test database.
-        # the side effect of initializing the test database.
+        self.connection.ensure_connection()
-        self.connection.cursor()
 
         return test_database_name
 

django/contrib/sites/management.py

@@ -33,7 +33,7 @@ def create_default_site(app_config, verbosity=2, interactive=True, db=DEFAULT_DB
         if sequence_sql:
             if verbosity >= 2:
                 print("Resetting sequence")
-            cursor = connections[db].cursor()
+            with connections[db].cursor() as cursor:
                 for command in sequence_sql:
                     cursor.execute(command)
 

django/core/cache/backends/db.py

@@ -59,8 +59,8 @@ class DatabaseCache(BaseDatabaseCache):
         self.validate_key(key)
         db = router.db_for_read(self.cache_model_class)
         table = connections[db].ops.quote_name(self._table)
-        cursor = connections[db].cursor()
 
+        with connections[db].cursor() as cursor:
             cursor.execute("SELECT cache_key, value, expires FROM %s "
                            "WHERE cache_key = %%s" % table, [key])
             row = cursor.fetchone()
@@ -75,7 +75,7 @@ class DatabaseCache(BaseDatabaseCache):
             expires = typecast_timestamp(str(expires))
         if expires < now:
             db = router.db_for_write(self.cache_model_class)
-            cursor = connections[db].cursor()
+            with connections[db].cursor() as cursor:
                 cursor.execute("DELETE FROM %s "
                                "WHERE cache_key = %%s" % table, [key])
             return default
@@ -96,8 +96,8 @@ class DatabaseCache(BaseDatabaseCache):
         timeout = self.get_backend_timeout(timeout)
         db = router.db_for_write(self.cache_model_class)
         table = connections[db].ops.quote_name(self._table)
-        cursor = connections[db].cursor()
 
+        with connections[db].cursor() as cursor:
             cursor.execute("SELECT COUNT(*) FROM %s" % table)
             num = cursor.fetchone()[0]
             now = timezone.now()
@@ -152,8 +152,8 @@ class DatabaseCache(BaseDatabaseCache):
 
         db = router.db_for_write(self.cache_model_class)
         table = connections[db].ops.quote_name(self._table)
-        cursor = connections[db].cursor()
 
+        with connections[db].cursor() as cursor:
             cursor.execute("DELETE FROM %s WHERE cache_key = %%s" % table, [key])
 
     def has_key(self, key, version=None):
@@ -162,13 +162,14 @@ class DatabaseCache(BaseDatabaseCache):
 
         db = router.db_for_read(self.cache_model_class)
         table = connections[db].ops.quote_name(self._table)
-        cursor = connections[db].cursor()
 
         if settings.USE_TZ:
             now = datetime.utcnow()
         else:
             now = datetime.now()
         now = now.replace(microsecond=0)
+
+        with connections[db].cursor() as cursor:
             cursor.execute("SELECT cache_key FROM %s "
                            "WHERE cache_key = %%s and expires > %%s" % table,
                            [key, connections[db].ops.value_to_db_datetime(now)])
@@ -197,7 +198,7 @@ class DatabaseCache(BaseDatabaseCache):
     def clear(self):
         db = router.db_for_write(self.cache_model_class)
         table = connections[db].ops.quote_name(self._table)
-        cursor = connections[db].cursor()
+        with connections[db].cursor() as cursor:
             cursor.execute('DELETE FROM %s' % table)
 
 

django/core/management/commands/createcachetable.py

@@ -72,7 +72,7 @@ class Command(BaseCommand):
             full_statement.append('    %s%s' % (line, ',' if i < len(table_output) - 1 else ''))
         full_statement.append(');')
         with transaction.commit_on_success_unless_managed():
-            curs = connection.cursor()
+            with connection.cursor() as curs:
                 try:
                     curs.execute("\n".join(full_statement))
                 except DatabaseError as e:

django/core/management/commands/flush.py

@@ -64,7 +64,7 @@ Are you sure you want to do this?
         if confirm == 'yes':
             try:
                 with transaction.commit_on_success_unless_managed():
-                    cursor = connection.cursor()
+                    with connection.cursor() as cursor:
                         for sql in sql_list:
                             cursor.execute(sql)
             except Exception as e:

django/core/management/commands/inspectdb.py

@@ -37,7 +37,7 @@ class Command(NoArgsCommand):
         table2model = lambda table_name: table_name.title().replace('_', '').replace(' ', '').replace('-', '')
         strip_prefix = lambda s: s[1:] if s.startswith("u'") else s
 
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             yield "# This is an auto-generated Django model module."
             yield "# You'll have to do the following manually to clean this up:"
             yield "#   * Rearrange models' order"

django/core/management/commands/loaddata.py

@@ -100,10 +100,9 @@ class Command(BaseCommand):
             if sequence_sql:
                 if self.verbosity >= 2:
                     self.stdout.write("Resetting sequences\n")
-                cursor = connection.cursor()
+                with connection.cursor() as cursor:
                     for line in sequence_sql:
                         cursor.execute(line)
-                cursor.close()
 
         if self.verbosity >= 1:
             if self.fixture_object_count == self.loaded_object_count:

django/core/management/commands/migrate.py

@@ -171,8 +171,9 @@ class Command(BaseCommand):
         "Runs the old syncdb-style operation on a list of app_labels."
         cursor = connection.cursor()
 
+        try:
             # Get a list of already installed *models* so that references work right.
-        tables = connection.introspection.table_names()
+            tables = connection.introspection.table_names(cursor)
             seen_models = connection.introspection.installed_models(tables)
             created_models = set()
             pending_references = {}
@@ -226,10 +227,12 @@ class Command(BaseCommand):
             # We force a commit here, as that was the previous behaviour.
             # If you can prove we don't need this, remove it.
             transaction.set_dirty(using=connection.alias)
+        finally:
+            cursor.close()
 
         # The connection may have been closed by a syncdb handler.
         cursor = connection.cursor()
-
+        try:
             # Install custom SQL for the app (but only if this
             # is a model we've just created)
             if self.verbosity >= 1:
@@ -270,6 +273,8 @@ class Command(BaseCommand):
                                         cursor.execute(sql)
                             except Exception as e:
                                 self.stderr.write("    Failed to install index for %s.%s model: %s\n" % (app_name, model._meta.object_name, e))
+        finally:
+            cursor.close()
 
         # Load initial_data fixtures (unless that has been disabled)
         if self.load_initial_data:

django/core/management/sql.py

@@ -67,6 +67,7 @@ def sql_delete(app_config, style, connection):
     except Exception:
         cursor = None
 
+    try:
         # Figure out which tables already exist
         if cursor:
             table_names = connection.introspection.table_names(cursor)
@@ -93,7 +94,7 @@ def sql_delete(app_config, style, connection):
         for model in app_models:
             if connection.introspection.table_name_converter(model._meta.db_table) in table_names:
                 output.extend(connection.creation.sql_destroy_model(model, references_to_delete, style))
-
+    finally:
         # Close database connection explicitly, in case this output is being piped
         # directly into a database client, to avoid locking issues.
         if cursor:

django/db/backends/__init__.py

@@ -194,13 +194,16 @@ class BaseDatabaseWrapper(object):
     ##### Backend-specific savepoint management methods #####
 
     def _savepoint(self, sid):
-        self.cursor().execute(self.ops.savepoint_create_sql(sid))
+        with self.cursor() as cursor:
+            cursor.execute(self.ops.savepoint_create_sql(sid))
 
     def _savepoint_rollback(self, sid):
-        self.cursor().execute(self.ops.savepoint_rollback_sql(sid))
+        with self.cursor() as cursor:
+            cursor.execute(self.ops.savepoint_rollback_sql(sid))
 
     def _savepoint_commit(self, sid):
-        self.cursor().execute(self.ops.savepoint_commit_sql(sid))
+        with self.cursor() as cursor:
+            cursor.execute(self.ops.savepoint_commit_sql(sid))
 
     def _savepoint_allowed(self):
         # Savepoints cannot be created outside a transaction
@@ -688,7 +691,7 @@ class BaseDatabaseFeatures(object):
             # otherwise autocommit will cause the confimation to
             # fail.
             self.connection.enter_transaction_management()
-            cursor = self.connection.cursor()
+            with self.connection.cursor() as cursor:
                 cursor.execute('CREATE TABLE ROLLBACK_TEST (X INT)')
                 self.connection.commit()
                 cursor.execute('INSERT INTO ROLLBACK_TEST (X) VALUES (8)')
@@ -1253,7 +1256,8 @@ class BaseDatabaseIntrospection(object):
         in sorting order between databases.
         """
         if cursor is None:
-            cursor = self.connection.cursor()
+            with self.connection.cursor() as cursor:
+                return sorted(self.get_table_list(cursor))
         return sorted(self.get_table_list(cursor))
 
     def get_table_list(self, cursor):

django/db/backends/creation.py

@@ -378,9 +378,8 @@ class BaseDatabaseCreation(object):
 
         call_command('createcachetable', database=self.connection.alias)
 
-        # Get a cursor (even though we don't need one yet). This has
+        # Ensure a connection for the side effect of initializing the test database.
-        # the side effect of initializing the test database.
+        self.connection.ensure_connection()
-        self.connection.cursor()
 
         return test_database_name
 
@@ -406,7 +405,7 @@ class BaseDatabaseCreation(object):
         qn = self.connection.ops.quote_name
 
         # Create the test database and connect to it.
-        cursor = self._nodb_connection.cursor()
+        with self._nodb_connection.cursor() as cursor:
             try:
                 cursor.execute(
                     "CREATE DATABASE %s %s" % (qn(test_database_name), suffix))
@@ -461,7 +460,7 @@ class BaseDatabaseCreation(object):
         # ourselves. Connect to the previous database (not the test database)
         # to do so, because it's not allowed to delete a database while being
         # connected to it.
-        cursor = self._nodb_connection.cursor()
+        with self._nodb_connection.cursor() as cursor:
             # Wait to avoid "database is being accessed by other users" errors.
             time.sleep(1)
             cursor.execute("DROP DATABASE %s"

django/db/backends/mysql/base.py

@@ -180,7 +180,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     @cached_property
     def _mysql_storage_engine(self):
         "Internal method used in Django tests. Don't rely on this from your code"
-        cursor = self.connection.cursor()
+        with self.connection.cursor() as 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
@@ -207,7 +207,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
             return False
 
         # Test if the time zone definitions are installed.
-        cursor = self.connection.cursor()
+        with self.connection.cursor() as cursor:
             cursor.execute("SELECT 1 FROM mysql.time_zone LIMIT 1")
             return cursor.fetchone() is not None
 
@@ -461,13 +461,12 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         return conn
 
     def init_connection_state(self):
-        cursor = self.connection.cursor()
+        with self.connection.cursor() as cursor:
             # SQL_AUTO_IS_NULL in MySQL controls whether an AUTO_INCREMENT column
             # on a recently-inserted row will return when the field is tested for
             # NULL.  Disabling this value brings this aspect of MySQL in line with
             # SQL standards.
             cursor.execute('SET SQL_AUTO_IS_NULL = 0')
-        cursor.close()
 
     def create_cursor(self):
         cursor = self.connection.cursor()

django/db/backends/oracle/base.py

@@ -353,7 +353,7 @@ WHEN (new.%(col_name)s IS NULL)
     def regex_lookup(self, lookup_type):
         # If regex_lookup is called before it's been initialized, then create
         # a cursor to initialize it and recur.
-        self.connection.cursor()
+        with self.connection.cursor():
             return self.connection.ops.regex_lookup(lookup_type)
 
     def return_insert_id(self):

django/db/backends/postgresql_psycopg2/base.py

@@ -149,7 +149,9 @@ class DatabaseWrapper(BaseDatabaseWrapper):
 
             if conn_tz != tz:
                 cursor = self.connection.cursor()
+                try:
                     cursor.execute(self.ops.set_time_zone_sql(), [tz])
+                finally:
                     cursor.close()
                 # Commit after setting the time zone (see #17062)
                 if not self.get_autocommit():

django/db/backends/postgresql_psycopg2/version.py

@@ -39,6 +39,6 @@ def get_version(connection):
     if hasattr(connection, 'server_version'):
         return connection.server_version
     else:
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             cursor.execute("SELECT version()")
             return _parse_version(cursor.fetchone()[0])

django/db/backends/schema.py

@@ -86,13 +86,12 @@ class BaseDatabaseSchemaEditor(object):
         """
         Executes the given SQL statement, with optional parameters.
         """
-        # Get the cursor
-        cursor = self.connection.cursor()
         # Log the command we're running, then run it
         logger.debug("%s; (params %r)" % (sql, params))
         if self.collect_sql:
             self.collected_sql.append((sql % tuple(map(self.connection.ops.quote_parameter, params))) + ";")
         else:
+            with self.connection.cursor() as cursor:
                 cursor.execute(sql, params)
 
     def quote_name(self, name):
@@ -791,7 +790,8 @@ class BaseDatabaseSchemaEditor(object):
         Returns all constraint names matching the columns and conditions
         """
         column_names = list(column_names) if column_names else None
-        constraints = self.connection.introspection.get_constraints(self.connection.cursor(), model._meta.db_table)
+        with self.connection.cursor() as cursor:
+            constraints = self.connection.introspection.get_constraints(cursor, model._meta.db_table)
         result = []
         for name, infodict in constraints.items():
             if column_names is None or column_names == infodict['columns']:

django/db/backends/sqlite3/base.py

@@ -122,7 +122,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         rule out support for STDDEV. We need to manually check
         whether the call works.
         """
-        cursor = self.connection.cursor()
+        with self.connection.cursor() as cursor:
             cursor.execute('CREATE TABLE STDDEV_TEST (X INT)')
             try:
                 cursor.execute('SELECT STDDEV(*) FROM STDDEV_TEST')

django/db/models/query.py

@@ -1522,6 +1522,7 @@ class RawQuerySet(object):
 
         query = iter(self.query)
 
+        try:
             # Find out which columns are model's fields, and which ones should be
             # annotated to the model.
             for pos, column in enumerate(self.columns):
@@ -1570,6 +1571,10 @@ class RawQuerySet(object):
                 instance._state.adding = False
 
                 yield instance
+        finally:
+            # Done iterating the Query. If it has its own cursor, close it.
+            if hasattr(self.query, 'cursor') and self.query.cursor:
+                self.query.cursor.close()
 
     def __repr__(self):
         text = self.raw_query

django/db/models/sql/compiler.py

@@ -1,4 +1,5 @@
 import datetime
+import sys
 
 from django.conf import settings
 from django.core.exceptions import FieldError
@@ -777,7 +778,7 @@ class SQLCompiler(object):
         cursor = self.connection.cursor()
         try:
             cursor.execute(sql, params)
-        except:
+        except Exception:
             cursor.close()
             raise
 
@@ -908,7 +909,7 @@ class SQLInsertCompiler(SQLCompiler):
     def execute_sql(self, return_id=False):
         assert not (return_id and len(self.query.objs) != 1)
         self.return_id = return_id
-        cursor = self.connection.cursor()
+        with self.connection.cursor() as cursor:
             for sql, params in self.as_sql():
                 cursor.execute(sql, params)
             if not (return_id and cursor):

tests/backends/tests.py

@@ -59,7 +59,7 @@ class OracleChecks(unittest.TestCase):
         # stored procedure through our cursor wrapper.
         from django.db.backends.oracle.base import convert_unicode
 
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             cursor.callproc(convert_unicode('DBMS_SESSION.SET_IDENTIFIER'),
                             [convert_unicode('_django_testing!')])
 
@@ -70,7 +70,7 @@ class OracleChecks(unittest.TestCase):
         # as query parameters.
         from django.db.backends.oracle.base import Database
 
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             var = cursor.var(Database.STRING)
             cursor.execute("BEGIN %s := 'X'; END; ", [var])
             self.assertEqual(var.getvalue(), 'X')
@@ -80,21 +80,21 @@ class OracleChecks(unittest.TestCase):
     def test_long_string(self):
         # If the backend is Oracle, test that we can save a text longer
         # than 4000 chars and read it properly
-        c = connection.cursor()
+        with connection.cursor() as cursor:
-        c.execute('CREATE TABLE ltext ("TEXT" NCLOB)')
+            cursor.execute('CREATE TABLE ltext ("TEXT" NCLOB)')
             long_str = ''.join(six.text_type(x) for x in xrange(4000))
-        c.execute('INSERT INTO ltext VALUES (%s)', [long_str])
+            cursor.execute('INSERT INTO ltext VALUES (%s)', [long_str])
-        c.execute('SELECT text FROM ltext')
+            cursor.execute('SELECT text FROM ltext')
-        row = c.fetchone()
+            row = cursor.fetchone()
             self.assertEqual(long_str, row[0].read())
-        c.execute('DROP TABLE ltext')
+            cursor.execute('DROP TABLE ltext')
 
     @unittest.skipUnless(connection.vendor == 'oracle',
                          "No need to check Oracle connection semantics")
     def test_client_encoding(self):
         # If the backend is Oracle, test that the client encoding is set
         # correctly.  This was broken under Cygwin prior to r14781.
-        connection.cursor()  # Ensure the connection is initialized.
+        self.connection.ensure_connection()
         self.assertEqual(connection.connection.encoding, "UTF-8")
         self.assertEqual(connection.connection.nencoding, "UTF-8")
 
@@ -103,12 +103,12 @@ class OracleChecks(unittest.TestCase):
     def test_order_of_nls_parameters(self):
         # an 'almost right' datetime should work with configured
         # NLS parameters as per #18465.
-        c = connection.cursor()
+        with connection.cursor() as cursor:
             query = "select 1 from dual where '1936-12-29 00:00' < sysdate"
             # Test that the query succeeds without errors - pre #18465 this
             # wasn't the case.
-        c.execute(query)
+            cursor.execute(query)
-        self.assertEqual(c.fetchone()[0], 1)
+            self.assertEqual(cursor.fetchone()[0], 1)
 
 
 class SQLiteTests(TestCase):
@@ -328,6 +328,12 @@ class PostgresVersionTest(TestCase):
             def fetchone(self):
                 return ["PostgreSQL 8.3"]
 
+            def __enter__(self):
+                return self
+
+            def __exit__(self, type, value, traceback):
+                pass
+
         class OlderConnectionMock(object):
             "Mock of psycopg2 (< 2.0.12) connection"
             def cursor(self):

tests/cache/tests.py

@@ -896,10 +896,9 @@ class DBCacheTests(BaseCacheTests, TransactionTestCase):
         management.call_command('createcachetable', verbosity=0, interactive=False)
 
     def drop_table(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             table_name = connection.ops.quote_name('test cache table')
             cursor.execute('DROP TABLE %s' % table_name)
-        cursor.close()
 
     def test_zero_cull(self):
         self._perform_cull_test(caches['zero_cull'], 50, 18)

tests/custom_methods/models.py

@@ -30,7 +30,7 @@ class Article(models.Model):
         database query for the sake of demonstration.
         """
         from django.db import connection
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             cursor.execute("""
                 SELECT id, headline, pub_date
                 FROM custom_methods_article

tests/initial_sql_regress/tests.py

@@ -28,7 +28,7 @@ class InitialSQLTests(TestCase):
         connection = connections[DEFAULT_DB_ALIAS]
         custom_sql = custom_sql_for_model(Simple, no_style(), connection)
         self.assertEqual(len(custom_sql), 9)
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             for sql in custom_sql:
                 cursor.execute(sql)
         self.assertEqual(Simple.objects.count(), 9)

tests/introspection/tests.py

@@ -23,7 +23,7 @@ class IntrospectionTests(TestCase):
                      "'%s' isn't in table_list()." % Article._meta.db_table)
 
     def test_django_table_names(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             cursor.execute('CREATE TABLE django_ixn_test_table (id INTEGER);')
             tl = connection.introspection.django_table_names()
             cursor.execute("DROP TABLE django_ixn_test_table;")
@@ -32,7 +32,7 @@ class IntrospectionTests(TestCase):
 
     def test_django_table_names_retval_type(self):
         # Ticket #15216
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             cursor.execute('CREATE TABLE django_ixn_test_table (id INTEGER);')
 
         tl = connection.introspection.django_table_names(only_existing=True)
@@ -53,13 +53,13 @@ class IntrospectionTests(TestCase):
                      'Reporter sequence not found in sequence_list()')
 
     def test_get_table_description_names(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             desc = connection.introspection.get_table_description(cursor, Reporter._meta.db_table)
         self.assertEqual([r[0] for r in desc],
                          [f.column for f in Reporter._meta.fields])
 
     def test_get_table_description_types(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             desc = connection.introspection.get_table_description(cursor, Reporter._meta.db_table)
         # The MySQL exception is due to the cursor.description returning the same constant for
         # text and blob columns. TODO: use information_schema database to retrieve the proper
@@ -75,7 +75,7 @@ class IntrospectionTests(TestCase):
     # inspect the length of character columns).
     @expectedFailureOnOracle
     def test_get_table_description_col_lengths(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             desc = connection.introspection.get_table_description(cursor, Reporter._meta.db_table)
         self.assertEqual(
             [r[3] for r in desc if datatype(r[1], r) == 'CharField'],
@@ -87,7 +87,7 @@ class IntrospectionTests(TestCase):
     # so its idea about null_ok in cursor.description is different from ours.
     @skipIfDBFeature('interprets_empty_strings_as_nulls')
     def test_get_table_description_nullable(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             desc = connection.introspection.get_table_description(cursor, Reporter._meta.db_table)
         self.assertEqual(
             [r[6] for r in desc],
@@ -97,14 +97,14 @@ class IntrospectionTests(TestCase):
     # Regression test for #9991 - 'real' types in postgres
     @skipUnlessDBFeature('has_real_datatype')
     def test_postgresql_real_type(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             cursor.execute("CREATE TABLE django_ixn_real_test_table (number REAL);")
             desc = connection.introspection.get_table_description(cursor, 'django_ixn_real_test_table')
             cursor.execute('DROP TABLE django_ixn_real_test_table;')
         self.assertEqual(datatype(desc[0][1], desc[0]), 'FloatField')
 
     def test_get_relations(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             relations = connection.introspection.get_relations(cursor, Article._meta.db_table)
 
         # Older versions of MySQL don't have the chops to report on this stuff,
@@ -117,7 +117,7 @@ class IntrospectionTests(TestCase):
 
     @skipUnlessDBFeature('can_introspect_foreign_keys')
     def test_get_key_columns(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             key_columns = connection.introspection.get_key_columns(cursor, Article._meta.db_table)
         self.assertEqual(
             set(key_columns),
@@ -125,12 +125,12 @@ class IntrospectionTests(TestCase):
                  ('response_to_id', Article._meta.db_table, 'id')]))
 
     def test_get_primary_key_column(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             primary_key_column = connection.introspection.get_primary_key_column(cursor, Article._meta.db_table)
         self.assertEqual(primary_key_column, 'id')
 
     def test_get_indexes(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             indexes = connection.introspection.get_indexes(cursor, Article._meta.db_table)
         self.assertEqual(indexes['reporter_id'], {'unique': False, 'primary_key': False})
 
@@ -139,7 +139,7 @@ class IntrospectionTests(TestCase):
         Test that multicolumn indexes are not included in the introspection
         results.
         """
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             indexes = connection.introspection.get_indexes(cursor, Reporter._meta.db_table)
         self.assertNotIn('first_name', indexes)
         self.assertIn('id', indexes)

tests/migrations/test_base.py

@@ -9,30 +9,37 @@ class MigrationTestBase(TransactionTestCase):
 
     available_apps = ["migrations"]
 
+    def get_table_description(self, table):
+        with connection.cursor() as cursor:
+            return connection.introspection.get_table_description(cursor, table)
+
     def assertTableExists(self, table):
-        self.assertIn(table, connection.introspection.get_table_list(connection.cursor()))
+        with connection.cursor() as cursor:
+            self.assertIn(table, connection.introspection.get_table_list(cursor))
 
     def assertTableNotExists(self, table):
-        self.assertNotIn(table, connection.introspection.get_table_list(connection.cursor()))
+        with connection.cursor() as cursor:
+            self.assertNotIn(table, connection.introspection.get_table_list(cursor))
 
     def assertColumnExists(self, table, column):
-        self.assertIn(column, [c.name for c in connection.introspection.get_table_description(connection.cursor(), table)])
+        self.assertIn(column, [c.name for c in self.get_table_description(table)])
 
     def assertColumnNotExists(self, table, column):
-        self.assertNotIn(column, [c.name for c in connection.introspection.get_table_description(connection.cursor(), table)])
+        self.assertNotIn(column, [c.name for c in self.get_table_description(table)])
 
     def assertColumnNull(self, table, column):
-        self.assertEqual([c.null_ok for c in connection.introspection.get_table_description(connection.cursor(), table) if c.name == column][0], True)
+        self.assertEqual([c.null_ok for c in self.get_table_description(table) if c.name == column][0], True)
 
     def assertColumnNotNull(self, table, column):
-        self.assertEqual([c.null_ok for c in connection.introspection.get_table_description(connection.cursor(), table) if c.name == column][0], False)
+        self.assertEqual([c.null_ok for c in self.get_table_description(table) if c.name == column][0], False)
 
     def assertIndexExists(self, table, columns, value=True):
+        with connection.cursor() as cursor:
             self.assertEqual(
                 value,
                 any(
                     c["index"]
-                for c in connection.introspection.get_constraints(connection.cursor(), table).values()
+                    for c in connection.introspection.get_constraints(cursor, table).values()
                     if c['columns'] == list(columns)
                 ),
             )

tests/migrations/test_operations.py

@@ -19,7 +19,7 @@ class OperationTests(MigrationTestBase):
         Creates a test model state and database table.
         """
         # Delete the tables if they already exist
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             try:
                 cursor.execute("DROP TABLE %s_pony" % app_label)
             except:
@@ -348,21 +348,21 @@ class OperationTests(MigrationTestBase):
         operation.state_forwards("test_alflpkfk", new_state)
         self.assertIsInstance(project_state.models["test_alflpkfk", "pony"].get_field_by_name("id"), models.AutoField)
         self.assertIsInstance(new_state.models["test_alflpkfk", "pony"].get_field_by_name("id"), models.FloatField)
-        # Test the database alteration
+
-        id_type = [c.type_code for c in connection.introspection.get_table_description(connection.cursor(), "test_alflpkfk_pony") if c.name == "id"][0]
+        def assertIdTypeEqualsFkType(self):
-        fk_type = [c.type_code for c in connection.introspection.get_table_description(connection.cursor(), "test_alflpkfk_rider") if c.name == "pony_id"][0]
+            with connection.cursor() as cursor:
+                id_type = [c.type_code for c in connection.introspection.get_table_description(cursor, "test_alflpkfk_pony") if c.name == "id"][0]
+                fk_type = [c.type_code for c in connection.introspection.get_table_description(cursor, "test_alflpkfk_rider") if c.name == "pony_id"][0]
             self.assertEqual(id_type, fk_type)
+        assertIdTypeEqualsFkType()
+        # Test the database alteration
         with connection.schema_editor() as editor:
             operation.database_forwards("test_alflpkfk", editor, project_state, new_state)
-        id_type = [c.type_code for c in connection.introspection.get_table_description(connection.cursor(), "test_alflpkfk_pony") if c.name == "id"][0]
+        assertIdTypeEqualsFkType()
-        fk_type = [c.type_code for c in connection.introspection.get_table_description(connection.cursor(), "test_alflpkfk_rider") if c.name == "pony_id"][0]
-        self.assertEqual(id_type, fk_type)
         # And test reversal
         with connection.schema_editor() as editor:
             operation.database_backwards("test_alflpkfk", editor, new_state, project_state)
-        id_type = [c.type_code for c in connection.introspection.get_table_description(connection.cursor(), "test_alflpkfk_pony") if c.name == "id"][0]
+        assertIdTypeEqualsFkType()
-        fk_type = [c.type_code for c in connection.introspection.get_table_description(connection.cursor(), "test_alflpkfk_rider") if c.name == "pony_id"][0]
-        self.assertEqual(id_type, fk_type)
 
     def test_rename_field(self):
         """
@@ -400,7 +400,7 @@ class OperationTests(MigrationTestBase):
         self.assertEqual(len(project_state.models["test_alunto", "pony"].options.get("unique_together", set())), 0)
         self.assertEqual(len(new_state.models["test_alunto", "pony"].options.get("unique_together", set())), 1)
         # Make sure we can insert duplicate rows
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             cursor.execute("INSERT INTO test_alunto_pony (id, pink, weight) VALUES (1, 1, 1)")
             cursor.execute("INSERT INTO test_alunto_pony (id, pink, weight) VALUES (2, 1, 1)")
             cursor.execute("DELETE FROM test_alunto_pony")

tests/requests/tests.py

@@ -725,7 +725,7 @@ class DatabaseConnectionHandlingTests(TransactionTestCase):
         # request_finished signal.
         response = self.client.get('/')
         # Make sure there is an open connection
-        connection.cursor()
+        self.connection.ensure_connection()
         connection.enter_transaction_management()
         signals.request_finished.send(sender=response._handler_class)
         self.assertEqual(len(connection.transaction_state), 0)

tests/schema/tests.py

@@ -37,7 +37,7 @@ class SchemaTests(TransactionTestCase):
 
     def delete_tables(self):
         "Deletes all model tables for our models for a clean test environment"
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             connection.disable_constraint_checking()
             table_names = connection.introspection.table_names(cursor)
             for model in self.models:
@@ -61,7 +61,7 @@ class SchemaTests(TransactionTestCase):
         connection.enable_constraint_checking()
 
     def column_classes(self, model):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             columns = dict(
                 (d[0], (connection.introspection.get_field_type(d[1], d), d))
                 for d in connection.introspection.get_table_description(
@@ -78,6 +78,20 @@ class SchemaTests(TransactionTestCase):
             raise DatabaseError("Table does not exist (empty pragma)")
         return columns
 
+    def get_indexes(self, table):
+        """
+        Get the indexes on the table using a new cursor.
+        """
+        with connection.cursor() as cursor:
+            return connection.introspection.get_indexes(cursor, table)
+
+    def get_constraints(self, table):
+        """
+        Get the constraints on a table using a new cursor.
+        """
+        with connection.cursor() as cursor:
+            return connection.introspection.get_constraints(cursor, table)
+
     # Tests
 
     def test_creation_deletion(self):
@@ -127,7 +141,7 @@ class SchemaTests(TransactionTestCase):
                 strict=True,
             )
         # Make sure the new FK constraint is present
-        constraints = connection.introspection.get_constraints(connection.cursor(), Book._meta.db_table)
+        constraints = self.get_constraints(Book._meta.db_table)
         for name, details in constraints.items():
             if details['columns'] == ["author_id"] and details['foreign_key']:
                 self.assertEqual(details['foreign_key'], ('schema_tag', 'id'))
@@ -342,7 +356,7 @@ class SchemaTests(TransactionTestCase):
             editor.create_model(TagM2MTest)
             editor.create_model(UniqueTest)
         # Ensure the M2M exists and points to TagM2MTest
-        constraints = connection.introspection.get_constraints(connection.cursor(), BookWithM2M._meta.get_field_by_name("tags")[0].rel.through._meta.db_table)
+        constraints = self.get_constraints(BookWithM2M._meta.get_field_by_name("tags")[0].rel.through._meta.db_table)
         if connection.features.supports_foreign_keys:
             for name, details in constraints.items():
                 if details['columns'] == ["tagm2mtest_id"] and details['foreign_key']:
@@ -363,7 +377,7 @@ class SchemaTests(TransactionTestCase):
             # Ensure old M2M is gone
             self.assertRaises(DatabaseError, self.column_classes, BookWithM2M._meta.get_field_by_name("tags")[0].rel.through)
             # Ensure the new M2M exists and points to UniqueTest
-            constraints = connection.introspection.get_constraints(connection.cursor(), new_field.rel.through._meta.db_table)
+            constraints = self.get_constraints(new_field.rel.through._meta.db_table)
             if connection.features.supports_foreign_keys:
                 for name, details in constraints.items():
                     if details['columns'] == ["uniquetest_id"] and details['foreign_key']:
@@ -388,7 +402,7 @@ class SchemaTests(TransactionTestCase):
         with connection.schema_editor() as editor:
             editor.create_model(Author)
         # Ensure the constraint exists
-        constraints = connection.introspection.get_constraints(connection.cursor(), Author._meta.db_table)
+        constraints = self.get_constraints(Author._meta.db_table)
         for name, details in constraints.items():
             if details['columns'] == ["height"] and details['check']:
                 break
@@ -404,7 +418,7 @@ class SchemaTests(TransactionTestCase):
                 new_field,
                 strict=True,
             )
-        constraints = connection.introspection.get_constraints(connection.cursor(), Author._meta.db_table)
+        constraints = self.get_constraints(Author._meta.db_table)
         for name, details in constraints.items():
             if details['columns'] == ["height"] and details['check']:
                 self.fail("Check constraint for height found")
@@ -416,7 +430,7 @@ class SchemaTests(TransactionTestCase):
                 Author._meta.get_field_by_name("height")[0],
                 strict=True,
             )
-        constraints = connection.introspection.get_constraints(connection.cursor(), Author._meta.db_table)
+        constraints = self.get_constraints(Author._meta.db_table)
         for name, details in constraints.items():
             if details['columns'] == ["height"] and details['check']:
                 break
@@ -527,7 +541,7 @@ class SchemaTests(TransactionTestCase):
             False,
             any(
                 c["index"]
-                for c in connection.introspection.get_constraints(connection.cursor(), "schema_tag").values()
+                for c in self.get_constraints("schema_tag").values()
                 if c['columns'] == ["slug", "title"]
             ),
         )
@@ -543,7 +557,7 @@ class SchemaTests(TransactionTestCase):
             True,
             any(
                 c["index"]
-                for c in connection.introspection.get_constraints(connection.cursor(), "schema_tag").values()
+                for c in self.get_constraints("schema_tag").values()
                 if c['columns'] == ["slug", "title"]
             ),
         )
@@ -561,7 +575,7 @@ class SchemaTests(TransactionTestCase):
             False,
             any(
                 c["index"]
-                for c in connection.introspection.get_constraints(connection.cursor(), "schema_tag").values()
+                for c in self.get_constraints("schema_tag").values()
                 if c['columns'] == ["slug", "title"]
             ),
         )
@@ -578,7 +592,7 @@ class SchemaTests(TransactionTestCase):
             True,
             any(
                 c["index"]
-                for c in connection.introspection.get_constraints(connection.cursor(), "schema_tagindexed").values()
+                for c in self.get_constraints("schema_tagindexed").values()
                 if c['columns'] == ["slug", "title"]
             ),
         )
@@ -627,7 +641,7 @@ class SchemaTests(TransactionTestCase):
         # Ensure the table is there and has the right index
         self.assertIn(
             "title",
-            connection.introspection.get_indexes(connection.cursor(), Book._meta.db_table),
+            self.get_indexes(Book._meta.db_table),
         )
         # Alter to remove the index
         new_field = CharField(max_length=100, db_index=False)
@@ -642,7 +656,7 @@ class SchemaTests(TransactionTestCase):
         # Ensure the table is there and has no index
         self.assertNotIn(
             "title",
-            connection.introspection.get_indexes(connection.cursor(), Book._meta.db_table),
+            self.get_indexes(Book._meta.db_table),
         )
         # Alter to re-add the index
         with connection.schema_editor() as editor:
@@ -655,7 +669,7 @@ class SchemaTests(TransactionTestCase):
         # Ensure the table is there and has the index again
         self.assertIn(
             "title",
-            connection.introspection.get_indexes(connection.cursor(), Book._meta.db_table),
+            self.get_indexes(Book._meta.db_table),
         )
         # Add a unique column, verify that creates an implicit index
         with connection.schema_editor() as editor:
@@ -665,7 +679,7 @@ class SchemaTests(TransactionTestCase):
             )
         self.assertIn(
             "slug",
-            connection.introspection.get_indexes(connection.cursor(), Book._meta.db_table),
+            self.get_indexes(Book._meta.db_table),
         )
         # Remove the unique, check the index goes with it
         new_field2 = CharField(max_length=20, unique=False)
@@ -679,7 +693,7 @@ class SchemaTests(TransactionTestCase):
             )
         self.assertNotIn(
             "slug",
-            connection.introspection.get_indexes(connection.cursor(), Book._meta.db_table),
+            self.get_indexes(Book._meta.db_table),
         )
 
     def test_primary_key(self):
@@ -691,7 +705,7 @@ class SchemaTests(TransactionTestCase):
             editor.create_model(Tag)
         # Ensure the table is there and has the right PK
         self.assertTrue(
-            connection.introspection.get_indexes(connection.cursor(), Tag._meta.db_table)['id']['primary_key'],
+            self.get_indexes(Tag._meta.db_table)['id']['primary_key'],
         )
         # Alter to change the PK
         new_field = SlugField(primary_key=True)
@@ -707,10 +721,10 @@ class SchemaTests(TransactionTestCase):
         # Ensure the PK changed
         self.assertNotIn(
             'id',
-            connection.introspection.get_indexes(connection.cursor(), Tag._meta.db_table),
+            self.get_indexes(Tag._meta.db_table),
         )
         self.assertTrue(
-            connection.introspection.get_indexes(connection.cursor(), Tag._meta.db_table)['slug']['primary_key'],
+            self.get_indexes(Tag._meta.db_table)['slug']['primary_key'],
         )
 
     def test_context_manager_exit(self):
@@ -741,7 +755,7 @@ class SchemaTests(TransactionTestCase):
         # Ensure the table is there and has an index on the column
         self.assertIn(
             column_name,
-            connection.introspection.get_indexes(connection.cursor(), BookWithLongName._meta.db_table),
+            self.get_indexes(BookWithLongName._meta.db_table),
         )
 
     def test_creation_deletion_reserved_names(self):

tests/transactions/tests.py

@@ -202,7 +202,8 @@ class AtomicTests(TransactionTestCase):
             # trigger a database error inside an inner atomic without savepoint
             with self.assertRaises(DatabaseError):
                 with transaction.atomic(savepoint=False):
-                    connection.cursor().execute(
+                    with connection.cursor() as cursor:
+                        cursor.execute(
                             "SELECT no_such_col FROM transactions_reporter")
             # prevent atomic from rolling back since we're recovering manually
             self.assertTrue(transaction.get_rollback())
@@ -534,7 +535,7 @@ class TransactionRollbackTests(IgnoreDeprecationWarningsMixin, TransactionTestCa
     available_apps = ['transactions']
 
     def execute_bad_sql(self):
-        cursor = connection.cursor()
+        with connection.cursor() as cursor:
             cursor.execute("INSERT INTO transactions_reporter (first_name, last_name) VALUES ('Douglas', 'Adams');")
 
     @skipUnlessDBFeature('requires_rollback_on_dirty_transaction')
@@ -678,6 +679,6 @@ class TransactionContextManagerTests(IgnoreDeprecationWarningsMixin, Transaction
         """
         with self.assertRaises(IntegrityError):
             with transaction.commit_on_success():
-                cursor = connection.cursor()
+                with connection.cursor() as cursor:
                     cursor.execute("INSERT INTO transactions_reporter (first_name, last_name) VALUES ('Douglas', 'Adams');")
         transaction.rollback()

tests/transactions_regress/tests.py

@@ -54,7 +54,7 @@ class TestTransactionClosing(IgnoreDeprecationWarningsMixin, TransactionTestCase
         @commit_on_success
         def raw_sql():
             "Write a record using raw sql under a commit_on_success decorator"
-            cursor = connection.cursor()
+            with connection.cursor() as cursor:
                 cursor.execute("INSERT into transactions_regress_mod (fld) values (18)")
 
         raw_sql()
@@ -143,7 +143,7 @@ class TestTransactionClosing(IgnoreDeprecationWarningsMixin, TransactionTestCase
             (reference). All this under commit_on_success, so the second insert should
             be committed.
             """
-            cursor = connection.cursor()
+            with connection.cursor() as cursor:
                 cursor.execute("INSERT into transactions_regress_mod (fld) values (2)")
                 transaction.rollback()
                 cursor.execute("INSERT into transactions_regress_mod (fld) values (2)")