新创建的 save() 上的 peewee 错误

Question

Making myself familiar with peewee, I stumbled upon the following weird behavior: Given a class similar to this

class Test(BaseModel):
    str = CharField(primary_key=True)

executing

instance = Test(str = 'something')
instance.save()

gives an obscure error complaining about some 'WHERE':

Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/peewee.py", line 3830, in execute_sql
    cursor.execute(sql, params or ())
sqlite3.OperationalError: near "WHERE": syntax error

During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.5/dist-packages/peewee.py", line 5165, in save
    rows = self.update(**field_dict).where(self._pk_expr()).execute()
  File "/usr/local/lib/python3.5/dist-packages/peewee.py", line 3458, in execute
    return self.database.rows_affected(self._execute())
  File "/usr/local/lib/python3.5/dist-packages/peewee.py", line 2939, in _execute
    return self.database.execute_sql(sql, params, self.require_commit)
  File "/usr/local/lib/python3.5/dist-packages/peewee.py", line 3837, in execute_sql
    self.commit()
  File "/usr/local/lib/python3.5/dist-packages/peewee.py", line 3656, in __exit__
    reraise(new_type, new_type(*exc_args), traceback)
  File "/usr/local/lib/python3.5/dist-packages/peewee.py", line 135, in reraise
    raise value.with_traceback(tb)
  File "/usr/local/lib/python3.5/dist-packages/peewee.py", line 3830, in execute_sql
    cursor.execute(sql, params or ())
peewee.OperationalError: near "WHERE": syntax error

However, directly creating the instance using

instance = Test.create(str = 'something')

works as expected. This only seems to happen when the attribute used is a primary key. A similar issue seems to be this question where no error is produced, but no database entry either. I'm aware of the workaround from the solution but just curious about this strange behavior.

Answer 1

You need to use save(force_insert=True) when using a non-auto-incrementing primary key.

http://docs.peewee-orm.com/en/latest/peewee/models.html#non-integer-primary-keys-composite-keys-and-other-tricks