猫鼬:查找具有多个条目的混合模式类型文档 [英] Mongoose: find mixed schema type documents with multiple entries

问题描述

我的数据模型大致如下:

My data model looks roughly like this:

data = {
    ...
    parameters: [{type:Schema.Types.mixed}],
    ...
}

如果我现在将文档插入数据库，

If i now insert a document into the database,

doc = {
  ...
  parameters:[{"foo":"bar"}],
  ...
}

我可以通过参数"键进行查询:

i can query it via the "parameters" key:

db.dataset.find({"parameters":[{"foo":"bar"}]},function(doc){
  ...
})

并取回预期的文档.但是，如果参数"包含多个键，例如

and get back the expected document. However if "parameters" contains more than one key, for example

doc = {
  ...
  parameters:[{"foo":"bar","ding":"dong"}]
  ...
}

我找不到它了.为什么?

i cant find it anymore. Why?

推荐答案

这是因为查询无法匹配数组字段parameters具有确切的数组对象作为其值[{"foo": "bar", "ding": "dong"}]的任何文档.为了说明这一点，让我们在集合中插入几个示例文档:

It is because the query cannot match any documents where the array field parameters has the exact array object as its value [{"foo": "bar", "ding": "dong"}]. To demonstrate this, let's insert a couple of sample documents in a collection:

/* 0 */
{
    "_id" : ObjectId("551d777fcfd33f4e2a61e48f"),
    "parameters" : [ 
        {
            "foo" : "bar"
        }
    ]
}

/* 1 */
{
    "_id" : ObjectId("551d777fcfd33f4e2a61e490"),
    "parameters" : [ 
        {
            "foo" : "bar",
            "ding" : "dong"
        }
    ]
}

使用该对象数组[{"foo":"bar"}]在此集合中查询parameters数组，将带"_id"的文档出现:ObjectId("551d777fcfd33f4e2a61e48f").但是，如果将查询对象更改为使用 $elemMatch ，那么它将同时带来两个文档:

Querying this collection for parameters array with this object array [{"foo":"bar"}] will bring the document with "_id" : ObjectId("551d777fcfd33f4e2a61e48f"). However, if you change your query object to use $elemMatch then it will bring both documents:

db.collection.find({"parameters": { "$elemMatch": { "foo": "bar" } }});

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