Fixed #33379 -- Added minimum database version checks.

Thanks Tim Graham for the review.

16 files changed, 166 insertions, 41 deletions

diff --git a/django/db/backends/base/base.py b/django/db/backends/base/base.py
index d2e79c1dd4..f093f2bd8b 100644
--- a/django/db/backends/base/base.py
+++ b/django/db/backends/base/base.py
@@ -13,7 +13,7 @@ except ImportError:
 
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
-from django.db import DEFAULT_DB_ALIAS, DatabaseError
+from django.db import DEFAULT_DB_ALIAS, DatabaseError, NotSupportedError
 from django.db.backends import utils
 from django.db.backends.base.validation import BaseDatabaseValidation
 from django.db.backends.signals import connection_created
@@ -24,6 +24,7 @@ from django.utils.asyncio import async_unsafe
 from django.utils.functional import cached_property
 
 NO_DB_ALIAS = "__no_db__"
+RAN_DB_VERSION_CHECK = set()
 
 
 # RemovedInDjango50Warning
@@ -185,6 +186,29 @@ class BaseDatabaseWrapper:
             )
         return list(self.queries_log)
 
+    def get_database_version(self):
+        """Return a tuple of the database's version."""
+        raise NotImplementedError(
+            "subclasses of BaseDatabaseWrapper may require a get_database_version() "
+            "method."
+        )
+
+    def check_database_version_supported(self):
+        """
+        Raise an error if the database version isn't supported by this
+        version of Django.
+        """
+        if (
+            self.features.minimum_database_version is not None
+            and self.get_database_version() < self.features.minimum_database_version
+        ):
+            db_version = ".".join(map(str, self.get_database_version()))
+            min_db_version = ".".join(map(str, self.features.minimum_database_version))
+            raise NotSupportedError(
+                f"{self.display_name} {min_db_version} or later is required "
+                f"(found {db_version})."
+            )
+
     # ##### Backend-specific methods for creating connections and cursors #####
 
     def get_connection_params(self):
@@ -203,10 +227,10 @@ class BaseDatabaseWrapper:
 
     def init_connection_state(self):
         """Initialize the database connection settings."""
-        raise NotImplementedError(
-            "subclasses of BaseDatabaseWrapper may require an init_connection_state() "
-            "method"
-        )
+        global RAN_DB_VERSION_CHECK
+        if self.alias not in RAN_DB_VERSION_CHECK:
+            self.check_database_version_supported()
+            RAN_DB_VERSION_CHECK.add(self.alias)
 
     def create_cursor(self, name=None):
         """Create a cursor. Assume that a connection is established."""
diff --git a/django/db/backends/base/features.py b/django/db/backends/base/features.py
index 42399b769a..ccf9104c21 100644
--- a/django/db/backends/base/features.py
+++ b/django/db/backends/base/features.py
@@ -3,6 +3,8 @@ from django.utils.functional import cached_property
 
 
 class BaseDatabaseFeatures:
+    # An optional tuple indicating the minimum supported database version.
+    minimum_database_version = None
     gis_enabled = False
     # Oracle can't group by LOB (large object) data types.
     allows_group_by_lob = True
diff --git a/django/db/backends/mysql/base.py b/django/db/backends/mysql/base.py
index 1c20554b4d..ca12917322 100644
--- a/django/db/backends/mysql/base.py
+++ b/django/db/backends/mysql/base.py
@@ -200,6 +200,9 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     ops_class = DatabaseOperations
     validation_class = DatabaseValidation
 
+    def get_database_version(self):
+        return self.mysql_version
+
     def get_connection_params(self):
         kwargs = {
             "conv": django_conversions,
@@ -251,6 +254,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         return connection
 
     def init_connection_state(self):
+        super().init_connection_state()
         assignments = []
         if self.features.is_sql_auto_is_null_enabled:
             # SQL_AUTO_IS_NULL controls whether an AUTO_INCREMENT column on
diff --git a/django/db/backends/mysql/features.py b/django/db/backends/mysql/features.py
index e27e766e48..f5b9ef9b55 100644
--- a/django/db/backends/mysql/features.py
+++ b/django/db/backends/mysql/features.py
@@ -49,6 +49,13 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     order_by_nulls_first = True
 
     @cached_property
+    def minimum_database_version(self):
+        if self.connection.mysql_is_mariadb:
+            return (10, 2)
+        else:
+            return (5, 7)
+
+    @cached_property
     def test_collations(self):
         charset = "utf8"
         if self.connection.mysql_is_mariadb and self.connection.mysql_version >= (
diff --git a/django/db/backends/oracle/base.py b/django/db/backends/oracle/base.py
index 7cbee768ea..2ccd3bc028 100644
--- a/django/db/backends/oracle/base.py
+++ b/django/db/backends/oracle/base.py
@@ -239,6 +239,9 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         )
         self.features.can_return_columns_from_insert = use_returning_into
 
+    def get_database_version(self):
+        return self.oracle_version
+
     def get_connection_params(self):
         conn_params = self.settings_dict["OPTIONS"].copy()
         if "use_returning_into" in conn_params:
@@ -255,6 +258,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         )
 
     def init_connection_state(self):
+        super().init_connection_state()
         cursor = self.create_cursor()
         # Set the territory first. The territory overrides NLS_DATE_FORMAT
         # and NLS_TIMESTAMP_FORMAT to the territory default. When all of
diff --git a/django/db/backends/oracle/features.py b/django/db/backends/oracle/features.py
index 257c3e1b87..2580e5c6c1 100644
--- a/django/db/backends/oracle/features.py
+++ b/django/db/backends/oracle/features.py
@@ -4,6 +4,7 @@ from django.utils.functional import cached_property
 
 
 class DatabaseFeatures(BaseDatabaseFeatures):
+    minimum_database_version = (19,)
     # Oracle crashes with "ORA-00932: inconsistent datatypes: expected - got
     # BLOB" when grouping by LOBs (#24096).
     allows_group_by_lob = False
diff --git a/django/db/backends/postgresql/base.py b/django/db/backends/postgresql/base.py
index 92f393227e..630da22964 100644
--- a/django/db/backends/postgresql/base.py
+++ b/django/db/backends/postgresql/base.py
@@ -153,6 +153,13 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     # PostgreSQL backend-specific attributes.
     _named_cursor_idx = 0
 
+    def get_database_version(self):
+        """
+        Return a tuple of the database's version.
+        E.g. for pg_version 120004, return (12, 4).
+        """
+        return divmod(self.pg_version, 10000)
+
     def get_connection_params(self):
         settings_dict = self.settings_dict
         # None may be used to connect to the default 'postgres' db
@@ -236,6 +243,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         return False
 
     def init_connection_state(self):
+        super().init_connection_state()
         self.connection.set_client_encoding("UTF8")
 
         timezone_changed = self.ensure_timezone()
diff --git a/django/db/backends/postgresql/features.py b/django/db/backends/postgresql/features.py
index 7c5d09d193..5e6752b97a 100644
--- a/django/db/backends/postgresql/features.py
+++ b/django/db/backends/postgresql/features.py
@@ -6,6 +6,7 @@ from django.utils.functional import cached_property
 
 
 class DatabaseFeatures(BaseDatabaseFeatures):
+    minimum_database_version = (10,)
     allows_group_by_selected_pks = True
     can_return_columns_from_insert = True
     can_return_rows_from_bulk_insert = True
diff --git a/django/db/backends/sqlite3/base.py b/django/db/backends/sqlite3/base.py
index 5bcd61eb96..8ca076a1d9 100644
--- a/django/db/backends/sqlite3/base.py
+++ b/django/db/backends/sqlite3/base.py
@@ -29,15 +29,6 @@ def decoder(conv_func):
     return lambda s: conv_func(s.decode())
 
 
-def check_sqlite_version():
-    if Database.sqlite_version_info < (3, 9, 0):
-        raise ImproperlyConfigured(
-            "SQLite 3.9.0 or later is required (found %s)." % Database.sqlite_version
-        )
-
-
-check_sqlite_version()
-
 Database.register_converter("bool", b"1".__eq__)
 Database.register_converter("time", decoder(parse_time))
 Database.register_converter("datetime", decoder(parse_datetime))
@@ -168,6 +159,9 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         kwargs.update({"check_same_thread": False, "uri": True})
         return kwargs
 
+    def get_database_version(self):
+        return self.Database.sqlite_version_info
+
     @async_unsafe
     def get_new_connection(self, conn_params):
         conn = Database.connect(**conn_params)
@@ -179,9 +173,6 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         conn.execute("PRAGMA legacy_alter_table = OFF")
         return conn
 
-    def init_connection_state(self):
-        pass
-
     def create_cursor(self, name=None):
         return self.connection.cursor(factory=SQLiteCursorWrapper)
 
diff --git a/django/db/backends/sqlite3/features.py b/django/db/backends/sqlite3/features.py
index 9161ae3133..2886ecc3be 100644
--- a/django/db/backends/sqlite3/features.py
+++ b/django/db/backends/sqlite3/features.py
@@ -9,6 +9,7 @@ from .base import Database
 
 
 class DatabaseFeatures(BaseDatabaseFeatures):
+    minimum_database_version = (3, 9)
     test_db_allows_multiple_connections = False
     supports_unspecified_pk = True
     supports_timezones = False
diff --git a/docs/releases/4.1.txt b/docs/releases/4.1.txt
index 88d283ff65..936350979f 100644
--- a/docs/releases/4.1.txt
+++ b/docs/releases/4.1.txt
@@ -157,6 +157,18 @@ CSRF
 
 * ...
 
+Database backends
+~~~~~~~~~~~~~~~~~
+
+* Third-party database backends can now specify the minimum required version of
+  the database using the ``DatabaseFeatures.minimum_database_version``
+  attribute which is a tuple (e.g. ``(10, 0)`` means "10.0"). If a minimum
+  version is specified, backends must also implement
+  ``DatabaseWrapper.get_database_version()``, which returns a tuple of the
+  current database version. The backend's
+  ``DatabaseWrapper.init_connection_state()`` method must call ``super()`` in
+  order for the check to run.
+
 Decorators
 ~~~~~~~~~~
 
diff --git a/tests/backends/base/test_base.py b/tests/backends/base/test_base.py
index 00ef766d5d..57d22ce269 100644
--- a/tests/backends/base/test_base.py
+++ b/tests/backends/base/test_base.py
@@ -41,6 +41,19 @@ class DatabaseWrapperTests(SimpleTestCase):
         self.assertEqual(BaseDatabaseWrapper.display_name, "unknown")
         self.assertNotEqual(connection.display_name, "unknown")
 
+    def test_get_database_version(self):
+        with patch.object(BaseDatabaseWrapper, "__init__", return_value=None):
+            msg = (
+                "subclasses of BaseDatabaseWrapper may require a "
+                "get_database_version() method."
+            )
+            with self.assertRaisesMessage(NotImplementedError, msg):
+                BaseDatabaseWrapper().get_database_version()
+
+    def test_check_database_version_supported_with_none_as_database_version(self):
+        with patch.object(connection.features, "minimum_database_version", None):
+            connection.check_database_version_supported()
+
 
 class ExecuteWrapperTests(TestCase):
     @staticmethod
@@ -297,3 +310,25 @@ class ConnectionHealthChecksTests(SimpleTestCase):
         connection.commit()
         connection.set_autocommit(True)
         self.assertIs(new_connection, connection.connection)
+
+
+class MultiDatabaseTests(TestCase):
+    databases = {"default", "other"}
+
+    def test_multi_database_init_connection_state_called_once(self):
+        for db in self.databases:
+            with self.subTest(database=db):
+                with patch.object(connections[db], "commit", return_value=None):
+                    with patch.object(
+                        connections[db],
+                        "check_database_version_supported",
+                    ) as mocked_check_database_version_supported:
+                        connections[db].init_connection_state()
+                        after_first_calls = len(
+                            mocked_check_database_version_supported.mock_calls
+                        )
+                        connections[db].init_connection_state()
+                        self.assertEqual(
+                            len(mocked_check_database_version_supported.mock_calls),
+                            after_first_calls,
+                        )
diff --git a/tests/backends/mysql/tests.py b/tests/backends/mysql/tests.py
index 139b363bf4..e84762584a 100644
--- a/tests/backends/mysql/tests.py
+++ b/tests/backends/mysql/tests.py
@@ -1,8 +1,9 @@
 import unittest
 from contextlib import contextmanager
+from unittest import mock
 
 from django.core.exceptions import ImproperlyConfigured
-from django.db import connection
+from django.db import NotSupportedError, connection
 from django.test import TestCase, override_settings
 
 
@@ -99,3 +100,19 @@ class IsolationLevelTests(TestCase):
         )
         with self.assertRaisesMessage(ImproperlyConfigured, msg):
             new_connection.cursor()
+
+
+@unittest.skipUnless(connection.vendor == "mysql", "MySQL tests")
+class Tests(TestCase):
+    @mock.patch.object(connection, "get_database_version")
+    def test_check_database_version_supported(self, mocked_get_database_version):
+        if connection.mysql_is_mariadb:
+            mocked_get_database_version.return_value = (10, 1)
+            msg = "MariaDB 10.2 or later is required (found 10.1)."
+        else:
+            mocked_get_database_version.return_value = (5, 6)
+            msg = "MySQL 5.7 or later is required (found 5.6)."
+
+        with self.assertRaisesMessage(NotSupportedError, msg):
+            connection.check_database_version_supported()
+        self.assertTrue(mocked_get_database_version.called)
diff --git a/tests/backends/oracle/tests.py b/tests/backends/oracle/tests.py
index 3f51d57de8..9a4e8ad435 100644
--- a/tests/backends/oracle/tests.py
+++ b/tests/backends/oracle/tests.py
@@ -1,14 +1,15 @@
 import unittest
+from unittest import mock
 
-from django.db import DatabaseError, connection
+from django.db import DatabaseError, NotSupportedError, connection
 from django.db.models import BooleanField
-from django.test import TransactionTestCase
+from django.test import TestCase, TransactionTestCase
 
 from ..models import Square, VeryLongModelNameZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
 
 
 @unittest.skipUnless(connection.vendor == "oracle", "Oracle tests")
-class Tests(unittest.TestCase):
+class Tests(TestCase):
     def test_quote_name(self):
         """'%' chars are escaped for query execution."""
         name = '"SOME%NAME"'
@@ -56,6 +57,17 @@ class Tests(unittest.TestCase):
                 field.set_attributes_from_name("is_nice")
                 self.assertIn('"IS_NICE" IN (0,1)', field.db_check(connection))
 
+    @mock.patch.object(
+        connection,
+        "get_database_version",
+        return_value=(18, 1),
+    )
+    def test_check_database_version_supported(self, mocked_get_database_version):
+        msg = "Oracle 19 or later is required (found 18.1)."
+        with self.assertRaisesMessage(NotSupportedError, msg):
+            connection.check_database_version_supported()
+        self.assertTrue(mocked_get_database_version.called)
+
 
 @unittest.skipUnless(connection.vendor == "oracle", "Oracle tests")
 class TransactionalTests(TransactionTestCase):
diff --git a/tests/backends/postgresql/tests.py b/tests/backends/postgresql/tests.py
index af08f6f286..ce8ed7b4d5 100644
--- a/tests/backends/postgresql/tests.py
+++ b/tests/backends/postgresql/tests.py
@@ -4,7 +4,13 @@ from io import StringIO
 from unittest import mock
 
 from django.core.exceptions import ImproperlyConfigured
-from django.db import DEFAULT_DB_ALIAS, DatabaseError, connection, connections
+from django.db import (
+    DEFAULT_DB_ALIAS,
+    DatabaseError,
+    NotSupportedError,
+    connection,
+    connections,
+)
 from django.db.backends.base.base import BaseDatabaseWrapper
 from django.test import TestCase, override_settings
 
@@ -303,3 +309,15 @@ class Tests(TestCase):
             [q["sql"] for q in connection.queries],
             [copy_expert_sql, "COPY django_session TO STDOUT"],
         )
+
+    def test_get_database_version(self):
+        new_connection = connection.copy()
+        new_connection.pg_version = 110009
+        self.assertEqual(new_connection.get_database_version(), (11, 9))
+
+    @mock.patch.object(connection, "get_database_version", return_value=(9, 6))
+    def test_check_database_version_supported(self, mocked_get_database_version):
+        msg = "PostgreSQL 10 or later is required (found 9.6)."
+        with self.assertRaisesMessage(NotSupportedError, msg):
+            connection.check_database_version_supported()
+        self.assertTrue(mocked_get_database_version.called)
diff --git a/tests/backends/sqlite/tests.py b/tests/backends/sqlite/tests.py
index e167e09dcf..97505eaa36 100644
--- a/tests/backends/sqlite/tests.py
+++ b/tests/backends/sqlite/tests.py
@@ -4,10 +4,8 @@ import tempfile
 import threading
 import unittest
 from pathlib import Path
-from sqlite3 import dbapi2
 from unittest import mock
 
-from django.core.exceptions import ImproperlyConfigured
 from django.db import NotSupportedError, connection, transaction
 from django.db.models import Aggregate, Avg, CharField, StdDev, Sum, Variance
 from django.db.utils import ConnectionHandler
@@ -21,28 +19,11 @@ from django.test.utils import isolate_apps
 
 from ..models import Author, Item, Object, Square
 
-try:
-    from django.db.backends.sqlite3.base import check_sqlite_version
-except ImproperlyConfigured:
-    # Ignore "SQLite is too old" when running tests on another database.
-    pass
-
 
 @unittest.skipUnless(connection.vendor == "sqlite", "SQLite tests")
 class Tests(TestCase):
     longMessage = True
 
-    def test_check_sqlite_version(self):
-        msg = "SQLite 3.9.0 or later is required (found 3.8.11.1)."
-        with mock.patch.object(
-            dbapi2, "sqlite_version_info", (3, 8, 11, 1)
-        ), mock.patch.object(
-            dbapi2, "sqlite_version", "3.8.11.1"
-        ), self.assertRaisesMessage(
-            ImproperlyConfigured, msg
-        ):
-            check_sqlite_version()
-
     def test_aggregation(self):
         """Raise NotSupportedError when aggregating on date/time fields."""
         for aggregate in (Sum, Avg, Variance, StdDev):
@@ -125,6 +106,13 @@ class Tests(TestCase):
             connections["default"].close()
             self.assertTrue(os.path.isfile(os.path.join(tmp, "test.db")))
 
+    @mock.patch.object(connection, "get_database_version", return_value=(3, 8))
+    def test_check_database_version_supported(self, mocked_get_database_version):
+        msg = "SQLite 3.9 or later is required (found 3.8)."
+        with self.assertRaisesMessage(NotSupportedError, msg):
+            connection.check_database_version_supported()
+        self.assertTrue(mocked_get_database_version.called)
+
 
 @unittest.skipUnless(connection.vendor == "sqlite", "SQLite tests")
 @isolate_apps("backends")