Fixed #29928 -- Enabled deferred constraint checks on SQLite 3.20+.

Refs django#11665, django#14204.

Thanks Michel Samia for the report.

Author: charettes

django/db/backends/sqlite3/features.py

@@ -38,6 +38,9 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     # Is "ALTER TABLE ... RENAME COLUMN" supported?
     can_alter_table_rename_column = Database.sqlite_version_info >= (3, 25, 0)
     supports_parentheses_in_compound = False
+    # Deferred constraint checks can be emulated on SQLite < 3.20 but not in a
+    # reasonably performant way.
+    can_defer_constraint_checks = Database.version_info >= (3, 20, 0)
 
     @cached_property
     def supports_stddev(self):

docs/releases/2.2.txt

@@ -265,6 +265,11 @@ Tests
 * The new :setting:`ORACLE_MANAGED_FILES <TEST_ORACLE_MANAGED_FILES>` test
   database setting allows using Oracle Managed Files (OMF) tablespaces.
 
+* Deferrable database constraints are now checked at the end of each
+  :class:`~django.test.TestCase` test on SQLite 3.20+ as well. These checks
+  were previously skipped on SQLite because they required expensive table
+  introspection before version 3.20 introduced native support.
+
 URLs
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