Django ORM：获取DataBaseError的列

Question

有没有办法获取相关的表和列名，而不仅仅是这条消息？

django.db.utils.DataError: value too long for type character varying(16)

我不喜欢猜测或搜索相关栏目。

我们使用 django 1.6 和 PostgreSQL 9.3.6

完整的回溯

  File "/home/f/local/lib/python2.7/site-packages/django/db/models/base.py", line 545, in save
    force_update=force_update, update_fields=update_fields)
  File "/home/f/local/lib/python2.7/site-packages/django/db/models/base.py", line 573, in save_base
    updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
  File "/home/f/local/lib/python2.7/site-packages/django/db/models/base.py", line 654, in _save_table
    result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
  File "/home/f/local/lib/python2.7/site-packages/django/db/models/base.py", line 687, in _do_insert
    using=using, raw=raw)
  File "/home/f/local/lib/python2.7/site-packages/django/db/models/manager.py", line 232, in _insert
    return insert_query(self.model, objs, fields, **kwargs)
  File "/home/f/local/lib/python2.7/site-packages/django/db/models/query.py", line 1514, in insert_query
    return query.get_compiler(using=using).execute_sql(return_id)
  File "/home/f/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 903, in execute_sql
    cursor.execute(sql, params)
  File "/home/f/local/lib/python2.7/site-packages/django/db/backends/util.py", line 69, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/home/f/local/lib/python2.7/site-packages/django/db/backends/util.py", line 53, in execute
    return self.cursor.execute(sql, params)
  File "/home/f/local/lib/python2.7/site-packages/django/db/utils.py", line 99, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/home/f/local/lib/python2.7/site-packages/django/db/backends/util.py", line 53, in execute
    return self.cursor.execute(sql, params)
django.db.utils.DataError: value too long for type character varying(16)

Answer 1

没有办法简单地找出来。

这里的 Django 只是引用了 DB 所说的话，这是 postgres 的错误：

db=> INSERT INTO db_accesskeys (key, link) VALUES ('AAAAA...', 'BBBBB...');
ERROR:  value too long for type character varying(40)

postgresql 不会告诉你哪个太长，所以 django 也无法找出来。

一种解决方法是手动验证每个输入以匹配max_length（虽然我不确定 django 1.6 上的确切实现，但这是 1.8）：

def validate_length(model, field, value):
    if len(value) > model._meta.get_field(field).max_length:
        raise Exception(
            field + " of " + model._meta.model_name + " is too long (" + str(len(value)) + " > " +
            str(model._meta.get_field(field).max_length) + ")"
    )


validate_length(AccessKeys, "key", "AAAAAAA...")
Exception: key of accesskeys is too long (109 > 40)

您当然可以根据需要调整抛出的异常，以便更轻松地访问过长的字段名称，或者准确查看它有多少个字符或...