Question

我正试图在couchDB中获取一些统计信息。文件结构是

[{
    _id: "1",
    name: "Hotel A",
    type: "hotel",
    stars: 3,
    flags: ["family-friendly","pet-friendly","green-hotel","sport"],
    hotelType: "premium",
    food: ["breakfast","lunch"]
}, {
    _id: "2",
    name: "Hotel B",
    type: "hotel",
    stars: 4,
    flags: ["family-friendly","pet-friendly"],
    hotelType: "budget",
    food: ["breakfast"]
}, {
    _id: "3",
    name: "Hotel C",
    type: "hotel",
    stars: 5,
    flags: ["family-friendly","pet-friendly"],
    hotelType: "budget",
    food: ["breakfast","lunch","dinner"]
}]

我如何获得酒店有多少“早餐”，“午餐”，“晚餐”并分类？我想得到这样的答案

{{breakfast:3},{lunch:2},{dinner:1}

}

或类似的东西。

Answer 1

最简单的方法是使用map函数，为每个文档发出该文档中food项的集合：

function (doc) {
  doc.food.forEach(function (item) {
    emit(iten, null)});
}

索引中的每个键现在只是一个食物项目。每个酒店和食品都有一把钥匙。到目前为止它看起来有点健谈：

$ curl -s 'http://localhost:5984/hotels/_design/so/_view/foods?reduce=false'
{"total_rows":6,"offset":0,"rows":[
{"id":"1","key":"breakfast","value":null},
{"id":"2","key":"breakfast","value":null},
{"id":"3","key":"breakfast","value":null},
{"id":"3","key":"dinner","value":null},
{"id":"1","key":"lunch","value":null},
{"id":"3","key":"lunch","value":null}
]}

但我们可以通过使用reduce步骤让couchdb为我们添加所有键。计算每个项目是一项常见的任务，它有一个特殊的erlang实现，只需使用“_count”作为reduce函数，然后，在使用视图时，使用group=true告诉它执行每个不同的密钥单独减少步骤。

$ curl -s 'http://localhost:5984/hotels/_design/so/_view/foods?group=true'
{"rows":[
{"key":"breakfast","value":3},
{"key":"dinner","value":1},
{"key":"lunch","value":2}
]}

couchdb排序和计数

1 个答案: