在CouchDb中查找重复值 [英] Find The Duplicate value in CouchDb

问题描述

我想在CouchDB中找到相同的值。我的地图是

I want to find same value in CouchDB. My Map is

function(doc) {
    var user = [];
if(doc.type = 'user'){
   user.push(doc.name);
    emit( doc.type, user);
  }
}

我得到的结果是

["Bob"],["Peter"],["Bob"] ....

我想减少点

["Bob","Peter","Bob"] 

或仅包含重复项的数组

["Bob","Bob"] 

我不了解reduce如何工作。
foreach value reduce是调用还是仅在映射完成时调用？

I don't understand How reduce works. foreach value reduce is called or only when the map is finished?

推荐答案

假设您有以下三个文档。

Let's say you have the following three documents.

鲍勃：

{
  "_id": "89d9ffe10a33df504ecc8d7c9a975eed",
  "_rev": "1-dfc3128d8d80760f2cf40328dd24553e",
  "type": "user",
  "name": "Bob"
}

Peter：

{
  "_id": "89d9ffe10a33df504ecc8d7c9a98a0c6",
  "_rev": "1-820e231c44f9b3125db79e0c00bbc050",
  "type": "user",
  "name": "Peter"
}

另一个鲍勃：

{
  "_id": "89d9ffe10a33df504ecc8d7c9a99f360",
  "_rev": "1-dfc3128d8d80760f2cf40328dd24553e",
  "type": "user",
  "name": "Bob"
}

您要查找具有重复的名称值的文档。只需使用以下地图功能在 name 字段上创建视图：

You want to find documents with duplicate name values. Simply create a view on the name field with the following map function:

function (doc) {
  if (doc.type == "user") {
    emit(doc.name);
  }
}

使用内置的 _count 缩小功能。如果使用 reduce = false 查询此视图，则会得到以下结果：

Use the built in _count reduce function. If you query this view with reduce=false, you will get the following results:

{
  total_rows: 3,
  offset: 0,
  rows: [
    {
      id: "89d9ffe10a33df504ecc8d7c9a975eed",
      key: "Bob",
      value: null
    },
    {
      id: "89d9ffe10a33df504ecc8d7c9a99f360",
      key: "Bob",
      value: null
    },
    {
      id: "89d9ffe10a33df504ecc8d7c9a98a0c6",
      key: "Peter",
      value: null
    }
  ]
}

由于这些结果是按名称，重复的 name 值将在结果中彼此相邻。

As these results are collated (sorted) by name, duplicate name values will be adjacent to each other in the results.

或者，您可以查询使用 group = true 的视图，您将得到以下结果：

Alternatively, you can query this view with group=true and you will get the following results:

{
  rows: [
    {
      key: "Bob",
      value: 2
    },
    {
      key: "Peter",
      value: 1
    }
  ]
}

任何值为 2 或更高的结果表示重复。确定了 Bob Bob 使用 reduce = false& = key Bob ，这将为您提供以下结果：

Any result with a value of 2 or greater indicates that there are duplicates. Having identified that there are duplicate entries for the key of "Bob", you can then query for all of the "Bob"s using reduce=false&key="Bob", which will give you the following results:

{
  total_rows: 3,
  offset: 1,
  rows: [
    {
      id: "89d9ffe10a33df504ecc8d7c9a975eed",
      key: "Bob",
      value: null
    },
    {
      id: "89d9ffe10a33df504ecc8d7c9a99f360",
      key: "Bob",
      value: null
    }
  ]
}

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