Refs #25530 -- Deleted deferred SQL references on delete operation.

django/db/backends/base/schema.py

@@ -314,6 +314,10 @@ class BaseDatabaseSchemaEditor:
         self.execute(self.sql_delete_table % {
             "table": self.quote_name(model._meta.db_table),
         })
+        # Remove all deferred statements referencing the deleted table.
+        for sql in list(self.deferred_sql):
+            if isinstance(sql, Statement) and sql.references_table(model._meta.db_table):
+                self.deferred_sql.remove(sql)
 
     def add_index(self, model, index):
         """Add an index on a model."""
@@ -456,6 +460,10 @@ class BaseDatabaseSchemaEditor:
         # Reset connection if required
         if self.connection.features.connection_persists_old_columns:
             self.connection.close()
+        # Remove all deferred statements referencing the deleted table.
+        for sql in list(self.deferred_sql):
+            if isinstance(sql, Statement) and sql.references_column(model._meta.db_table, field.column):
+                self.deferred_sql.remove(sql)
 
     def alter_field(self, model, old_field, new_field, strict=False):
         """

django/db/backends/sqlite3/schema.py

@@ -190,11 +190,6 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
             # Rename the old table to make way for the new
             self.alter_db_table(model, temp_model._meta.db_table, model._meta.db_table)
 
-            # Remove all deferred statements referencing the temporary table.
-            for sql in list(self.deferred_sql):
-                if isinstance(sql, Statement) and sql.references_table(temp_model._meta.db_table):
-                    self.deferred_sql.remove(sql)
-
             # Create a new table with the updated schema.
             self.create_model(temp_model)
 
@@ -226,6 +221,10 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
             self.execute(self.sql_delete_table % {
                 "table": self.quote_name(model._meta.db_table),
             })
+            # Remove all deferred statements referencing the deleted table.
+            for sql in list(self.deferred_sql):
+                if isinstance(sql, Statement) and sql.references_table(model._meta.db_table):
+                    self.deferred_sql.remove(sql)
 
     def add_field(self, model, field):
         """

tests/schema/tests.py

@@ -195,14 +195,15 @@ class SchemaTests(TransactionTestCase):
         """
         Tries creating a model's table, and then deleting it.
         """
-        # Create the table
         with connection.schema_editor() as editor:
+            # Create the table
             editor.create_model(Author)
             # The table is there
             list(Author.objects.all())
             # Clean up that table
-        with connection.schema_editor() as editor:
             editor.delete_model(Author)
+            # No deferred SQL should be left over.
+            self.assertEqual(editor.deferred_sql, [])
         # The table is gone
         with self.assertRaises(DatabaseError):
             list(Author.objects.all())
@@ -379,6 +380,17 @@ class SchemaTests(TransactionTestCase):
         self.assertEqual(columns['age'][0], "IntegerField")
         self.assertEqual(columns['age'][1][6], True)
 
+    def test_add_field_remove_field(self):
+        """
+        Adding a field and removing it removes all deferred sql referring to it.
+        """
+        with connection.schema_editor() as editor:
+            # Create a table with a unique constraint on the slug field.
+            editor.create_model(Tag)
+            # Remove the slug column.
+            editor.remove_field(Tag, Tag._meta.get_field('slug'))
+        self.assertEqual(editor.deferred_sql, [])
+
     def test_add_field_temp_default(self):
         """
         Tests adding fields to models with a temporary default