MongoDB聚合具有链接对象的管道

本文介绍了MongoDB聚合具有链接对象的管道的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我要在一个查询中链接两个对象，并对其使用聚合函数.一些数据已本地化，我正在使用此处中的解决方案来获取指定数据区域设置.

I'm linking two objects in one query and use aggregate function for it. Some data is localized and I'm using a solution from here to get data for specified locale.

我正在努力对链接对象(房间)中的数据进行同样的处理.具体来说，请从roomDetails中列出给定语言环境的数据.

I am struggling to do the same with data from the linked object (rooms). Specifically, list data for given locale from the roomDetails.

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推荐答案

您只需要在要过滤 roomTypes 并休息的第二个 $ addFields 阶段添加过滤器阶段是相同的，只是在下面从开始注释和结束注释中突出显示了新代码，

You just need to add filter in your second $addFields stage that you are filtering roomTypes and rest of the stages would be same, just highlighted the new code in below from start comment and end comment,

我建议您在已实现的查询中使用此解决方案，但不确定这样做是否正确，可能会导致查询性能下降.

I am suggesting this solution in your implemented query, i am not sure this is the right approach to do this, might be more will cause the performance of query.

• $ reduce 迭代 roomDetails.description 数组$ cond的循环以匹配本地并将匹配结果返回给值，对于 roomDetails.title进行相同的处理数组，并使用 $ mergeObjects
将这2个更新的字段与当前对象合并
• $reduce to iterate loop of roomDetails.description array $cond to match local and return match result to value, same process for roomDetails.title array, and merge this 2 updated fields with current object using $mergeObjects
{ $addFields: { roomTypes: { $map: { input: "$roomTypes", in: { $mergeObjects: [ "$$this", {

开始:

roomDetails: { $mergeObjects: [ "$$this.roomDetails", { description: { $reduce: { input: "$$this.roomDetails.description", initialValue: "", in: { $cond: [ { $eq: ["$$this.locale", "pl"] }, "$$this.value", "$$value" ] } } }, title: { $reduce: { input: "$$this.roomDetails.title", initialValue: "", in: { $cond: [ { $eq: ["$$this.locale", "pl"] }, "$$this.value", "$$value" ] } } } } ] },

〜结束〜

available: { $reduce: { input: "$$this.capacity", initialValue: 0, in: { $cond: [ { $eq: ["$$this.cruiseID", "$cruiseID"] }, "$$this.available", "$$value" ] } } } } ] } } } } }

游乐场

在通用选项中，我已经在您的参考问题中回答了，您可以使用类似的功能，

In generic option i have answered in your reference question you can use same function like,

function languageFilter(inputField, locale) { return { $reduce: { input: inputField, initialValue: "", in: { $cond: [{ $eq: ["$$this.locale", locale] }, "$$this.value", "$$value"] } } }; }

您的最终查询将是:

let locale = "pl"; db.cs.aggregate([ { $match: { cID: "00001" } }, { $lookup: { from: "rooms", localField: "roomTypes.roomID", foreignField: "roomID", as: "roomTypes" } }, { $addFields: { title: languageFilter("$title", locale), description: languageFilter("$description", locale), roomTypes: { $map: { input: "$roomTypes", in: { $mergeObjects: [ "$$this", { roomDetails: { $mergeObjects: [ "$$this.roomDetails", { description: languageFilter("$$this.roomDetails.description", locale), title: languageFilter("$$this.roomDetails.title", locale) } ] }, available: { $reduce: { input: "$$this.capacity", initialValue: 0, in: { $cond: [ { $eq: ["$$this.cruiseID", "$cruiseID"] }, "$$this.available", "$$value" ] } } } } ] } } } } }, { $project: { _id: 0, "roomTypes": { _id: 0 }, "roomTypes.capacity": 0 } } ]);