索引和查询数组，使用cloudant和couchdb 2.0的芒果查询 [英] index and query items in an array with mango query for cloudant and couchdb 2.0

问题描述

我具有以下数据库结构:

I have the following db structure:

{"_id": "0096874","genre": ["Adventure","Comedy", "Sci-Fi" ]}
{"_id": "0099088","genre": ["Comedy", "Sci-Fi", "Western"]}

并希望像在mongodb中一样进行查询

and like to query it like I could do in mongodb

db.movies.find({genre: {$in: ["Comedy"]}})

当我在整个数据库中使用文本索引时，它可以工作，但这似乎非常浪费:

It works when i use a text index for the whole database, but that seems very wasteful:

// index
    {
      "index": {},
      "type": "text"
    }
//query
{
  "selector": {
    "genre": {
      "$in": ["Comedy"]
    }
  },
  "fields": [
    "_id",
    "genre"
  ]
}

以下索引不起作用:

{
  "index": {
    "fields": [
      "genre"
    ]
  },
  "type": "json"
}

什么是cloudant查询的正确索引，而不是整个数据库的索引? 谢谢您的帮助

What is the correct index for cloudant query, which does not index the whole db? Thanks for your help

推荐答案

您几乎完全正确.您的索引正确，但是您需要使用选择器来获取所有ID https ://cloudant.com/blog/mango-json-vs-text-indexes/.

You had it almost correct. Your index is right, but you need to throw in a selector to get all IDs https://cloudant.com/blog/mango-json-vs-text-indexes/.

正如Tony所说，这不是解决方案性能的好方法，

This isn't a great solution performance-wise, as Tony says,

之所以可行，是因为，Mango对所有文档执行上述$ in操作作为过滤机制.正如我们在上一节有关JSON语法的结论中所看到的，上述查询的性能折衷在于，它本质上执行完整索引扫描，然后应用过滤器.

{
  "selector": {
    "_id": {
      "$gt": null
    }, 
    "genre": {
      "$in": ["Western"]
    }
  },
  "fields": [
    "_id",
    "genre"
  ],
  "sort": [
    {
      "_id": "asc"
    }
  ]
}

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