id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
27180	Check for sql_mode fails during migration with special database connections	Markus Gerards	nobody	"I believe I found again a bug regarding some special database connections (like #26991):

Running `migrate` raises this error:


{{{
Traceback (most recent call last):
  File ""manage.py"", line 10, in <module>
    execute_from_command_line(sys.argv)
  File ""/usr/local/lib/python2.7/site-packages/django/core/management/__init__.py"", line 367, in execute_from_command_line
    utility.execute()
  File ""/usr/local/lib/python2.7/site-packages/django/core/management/__init__.py"", line 359, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File ""/usr/local/lib/python2.7/site-packages/django/core/management/base.py"", line 294, in run_from_argv
    self.execute(*args, **cmd_options)
  File ""/usr/local/lib/python2.7/site-packages/django/core/management/base.py"", line 342, in execute
    self.check()
  File ""/usr/local/lib/python2.7/site-packages/django/core/management/base.py"", line 374, in check
    include_deployment_checks=include_deployment_checks,
  File ""/usr/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py"", line 61, in _run_checks
    issues = run_checks(tags=[Tags.database])
  File ""/usr/local/lib/python2.7/site-packages/django/core/checks/registry.py"", line 81, in run_checks
    new_errors = check(app_configs=app_configs)
  File ""/usr/local/lib/python2.7/site-packages/django/core/checks/database.py"", line 10, in check_database_backends
    issues.extend(conn.validation.check(**kwargs))
  File ""/usr/local/lib/python2.7/site-packages/django/db/backends/mysql/validation.py"", line 9, in check
    issues.extend(self._check_sql_mode(**kwargs))
  File ""/usr/local/lib/python2.7/site-packages/django/db/backends/mysql/validation.py"", line 16, in _check_sql_mode
    modes = set(sql_mode[0].split(','))
TypeError: 'NoneType' object has no attribute '__getitem__'
}}}

The reason is, that `SELECT @@sql_mode` returns no results in my special case.

Just a little side note: `migrate` runs database checks against all database connections, no matter if a database is selected via the `--database` parameter or if migrations are not allowed because of a database router. I'm not quite sure if this works as intended."	Bug	closed	Database layer (models, ORM)	1.10	Release blocker	fixed			Accepted	0	0	0	0	0	0