Flask/Mongoengine：尝试使用静态方法对父 class 执行全文搜索时出错

Question

我创建了一个 Item class，以及两个子classes Item1 和 Item2，如下所示

class Item(db.Document):
    name            =   db.StringField()
    slug            =   db.StringField()
    description     =   db.StringField()
    content         =   db.StringField()
    start_time      =   db.DateTimeField()
    end_time        =   db.DateTimeField()

    @staticmethod
    def search_static(keywords):
        return Item.objects.search_text(keywords).order_by('$text_score')

    @classmethod
    def search_class(cls,keywords):
        return cls.objects.search_text(keywords).order_by('$text_score')

    meta = {
        'allow_inheritance' : True,
        'indexes'           : [
            {
                'fields': ['$name','$slug','$description','$content'],
                'default_language':'french',
                'weights': {'name': 10, 'slug': 10 , 'description': 5, 'content': 5}
            }
        ]
    }

class Item1(Item):
    item_type       =   db.ReferenceField('T1')

class Item2(Item):
    item_type       =   db.ReferenceField('T2')

class T1(db.Document):
    name            =   db.StringField()

class T2(db.Document):
    name            =   db.StringField()

接下来，我创建了一些项目

Results in mongo shell of following commands db.item.find() / db.t1.find() / db.t2.find()

当我测试 class 方法时一切正常

>>> Item1.search_class("dog")
[<Item1: Item1 object>, <Item1: Item1 object>]
>>> Item1.search_class("viper")
[<Item1: Item1 object>]
>>> Item2.search_class("viper")
[<Item2: Item2 object>]
>>> Item2.search_class("tiger")
[]
>>>

但是当我想使用静态方法时（为了一次搜索所有子classes），我有这个mongo错误：

>>> Item.search_static("tiger")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/venv/lib/python2.7/site-packages/mongoengine/queryset/queryset.py", line 58, in __repr__
    self._populate_cache()
  File "/venv/lib/python2.7/site-packages/mongoengine/queryset/queryset.py", line 92, in _populate_cache
    self._result_cache.append(self.next())
  File "/venv/lib/python2.7/site-packages/mongoengine/queryset/base.py", line 1407, in next
    raw_doc = self._cursor.next()
  File "/venv/lib/python2.7/site-packages/pymongo/cursor.py", line 1090, in next
    if len(self.__data) or self._refresh():
  File "/venv/lib/python2.7/site-packages/pymongo/cursor.py", line 1012, in _refresh
    self.__read_concern))
  File "/venv/lib/python2.7/site-packages/pymongo/cursor.py", line 905, in __send_message
    helpers._check_command_response(doc['data'][0])
  File "/venv/lib/python2.7/site-packages/pymongo/helpers.py", line 196, in _check_command_response
    raise OperationFailure(msg % errmsg, code, response)
pymongo.errors.OperationFailure: error processing query: ns=archives_flask.itemTree: $and
    _cls $in [ "Item" "Item.Item1" "Item.Item2" ]
    TEXT : query=tiger, language=french, caseSensitive=0, diacriticSensitive=0, tag=NULL
Sort: { _text_score: { $meta: "textScore" } }
Proj: { _text_score: { $meta: "textScore" } }
 planner returned error: failed to use text index to satisfy $text query (if text index is compound, are equality predicates given for all prefix fields?)
>>>

能否请您提供任何想法或提示？

Answer 1

我意识到这是一个很老的问题，但我在寻找完全相同问题的解决方案时发现了它，我想我会在这里记录我的发现以供后代使用。

问题是，当您 subclass a mongoengine.Document subclass 时，mongoengine 会自动添加 _cls 作为集合的索引。当您随后尝试使用父 class（Document 的直接子class）对该集合进行全文搜索时，mongoengine 将在查询此文档及其所有子 class 的所有可能 _cls 值。不幸的是，这是不允许的，as documented in the MongoDB docs:

If the compound text index includes keys preceding the text index key, to perform a $text search, the query predicate must include equality match conditions on the preceding keys.

请注意，如果您对其中一个子classes 进行文本搜索，它会完美运行 - 这是因为 mongoengine 在这种情况下使用相等谓词，这是完全有效的。

您可以通过将索引调整为不使用复合文本索引来解决此问题。在您的父文件 subclass（在本例中为 Item）调整您的 indexes 定义以将 cls 设置为 False:

meta = {
    'allow_inheritance' : True,
    'indexes'           : [
        {
            'fields': ['$name','$slug','$description','$content'],
            'default_language':'french',
            'weights': {'name': 10, 'slug': 10 , 'description': 5, 'content': 5},
            'cls': False
        }
    ]
}

这记录在 Mongoengine documentation 中。我希望这对以后遇到这个问题的人有所帮助！

Flask/Mongoengine：尝试使用静态方法对父 class 执行全文搜索时出错

Flask/Mongoengine : Error while trying to perform full-text-search on parent class with static method

static-methods

full-text-search

mongoengine

flask