如何在mongo中获取嵌入式数组的大小? [英] how to get embedded array's size in mongo?

问题描述

可能重复:
在MongoDB中查询内部数组大小

Possible Duplicate:
Querying internal array size in MongoDB

我有一个包含数组category的文档.我只想知道category中有多少个项目.我在文档中只能找到如何计算顶级文档的数量.

I have a document which contains an array category. I just want to know how many items there are in category. All I could find in the documentation is how to count the number of top level documents.

{
 "_id": {
     "$oid": "4e73a30466ca1a1f56000001"
    },
 "category": [
     "Food",
     "Entertainment"
    ]
}

推荐答案

添加新字段以处理类别大小.这是mongo世界中的常规做法.

Add new field to hande category size. It's a usual practice in mongo world.

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