Regnskab: Use select_for_update locking in SheetRowUpdate

[Mortal]

Purchase.objects.bulk_create in SheetRowUpdate.save_rows fails with django.db.utils.IntegrityError if another identical request deletes the SheetRow objects we just created.

Subject: [Django] ERROR (EXTERNAL IP): Internal Server Error:  /regnskab/sheet/202/edit/
Date: Mon, 1 May 2017 11:15:49 +0000

Internal Server Error: /regnskab/sheet/202/edit/
Traceback (most recent call last):
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/backends/mysql/base.py", line 124, in execute
    return self.cursor.execute(query, args)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/cursors.py", line 250, in execute
    self.errorhandler(self, exc, value)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/connections.py", line 42, in defaulterrorhandler
    raise errorvalue
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/cursors.py", line 247, in execute
    res = self._query(query)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/cursors.py", line 411, in _query
    rowcount = self._do_query(q)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/cursors.py", line 374, in _do_query
    db.query(q)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/connections.py", line 270, in query
    _mysql.connection.query(self, query)
_mysql_exceptions.IntegrityError: (1452, 'Cannot add or update a child row: a foreign key constraint fails (`tkweb`.`regnskab_purchase`, CONSTRAINT `regnskab_purchas_row_id_589fcda1fa570aac_fk_regnskab_sheetrow_id` FOREIGN KEY (`row_id`) REFERENCES `regnskab_sheetrow` (`id`))')

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/views/generic/base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/utils/decorators.py", line 34, in _wrapper
    return bound_func(*args, **kwargs)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/contrib/auth/decorators.py", line 22, in _wrapped_view
    return view_func(request, *args, **kwargs)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/utils/decorators.py", line 30, in bound_func
    return func.__get__(self, type(self))(*args2, **kwargs2)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/regnskab/views/base.py", line 223, in dispatch
    return super().dispatch(request, *args, **kwargs)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/views/generic/base.py", line 89, in dispatch
    return handler(request, *args, **kwargs)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/views/generic/edit.py", line 215, in post
    return self.form_valid(form)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/regnskab/views/base.py", line 380, in form_valid
    self.save_rows(row_objects)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/regnskab/views/base.py", line 369, in save_rows
    Purchase.objects.bulk_create(save_purchases)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/models/manager.py", line 127, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/models/query.py", line 392, in bulk_create
    self._batched_insert(objs_without_pk, fields, batch_size)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/models/query.py", line 937, in _batched_insert
    using=self.db)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/models/manager.py", line 127, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/models/query.py", line 920, in _insert
    return query.get_compiler(using=using).execute_sql(return_id)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 974, in execute_sql
    cursor.execute(sql, params)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/utils.py", line 98, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/django/db/backends/mysql/base.py", line 124, in execute
    return self.cursor.execute(query, args)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/cursors.py", line 250, in execute
    self.errorhandler(self, exc, value)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/connections.py", line 42, in defaulterrorhandler
    raise errorvalue
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/cursors.py", line 247, in execute
    res = self._query(query)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/cursors.py", line 411, in _query
    rowcount = self._do_query(q)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/cursors.py", line 374, in _do_query
    db.query(q)
  File "/home/tkammer/tkweb/venv/lib/python3.5/site-packages/MySQLdb/connections.py", line 270, in query
    _mysql.connection.query(self, query)
django.db.utils.IntegrityError: (1452, 'Cannot add or update a child row: a foreign key constraint fails (`tkweb`.`regnskab_purchase`, CONSTRAINT `regnskab_purchas_row_id_589fcda1fa570aac_fk_regnskab_sheetrow_id` FOREIGN KEY (`row_id`) REFERENCES `regnskab_sheetrow` (`id`))')