Mongoose 聚合错误：参数必须是聚合管道运算符答案

【问题标题】：Mongoose aggregation Error: Arguments must be aggregate pipeline operatorsMongoose 聚合错误：参数必须是聚合管道运算符
【发布时间】：2019-03-27 05:11:02
【问题描述】：

我已经编写了以下代码，用于根据我的要求聚合数据。当我在 robo 3t 中尝试时，这很有效。下面的代码有什么问题。它给出了错误，因为“参数必须是聚合管道运算符”。

db.model('KeywordRanking').aggregate([
                {
                    $match: {
                        user: req.user._id
                    }
                },
                {
                    $project: {
                        "keyword": 1,
                        "user": 1,
                        "website": 1,
                        "rank": 1,
                        "type": 1,
                        "createdDateStr": 1
                    }
                },
                {
                    $lookup: {
                        from: "keywords",
                        localField: "keyword",
                        foreignField: "_id",
                        as: "keyword_refs"
                    }
                },
                { $unwind: "$keyword_refs" },
                {
                    $group: {
                        "_id": { "keyword": "$keyword", "website": "$website" },
                        "website": { "$first": "$website" },
                        "user": { "$first": "$user" },
                        "type": { "$first": "$type" },
                        "ranks": { "$push": { "createdDateStr": "$createdDateStr", "rank": "$rank" } },
                        "keyword_refs": { "$addToSet": "$keyword_refs" }
                    }
                },
                { $limit: count },
                { $skip: skip }
            ], { allowDiskUse: true });

【问题讨论】：

标签： node.js mongodb mongoose aggregation-framework

【解决方案1】：

mongoose aggregate 仅接受管道数组和回调（如果需要承诺，请省略回调）

对于allowDiskUSe，您可以按如下方式使用此聚合助手

    db.model('KeywordRanking').aggregate([
            {
                $match: {
                    user: req.user._id
                }
            },
            {
                $project: {
                    "keyword": 1,
                    "user": 1,
                    "website": 1,
                    "rank": 1,
                    "type": 1,
                    "createdDateStr": 1
                }
            },
            {
                $lookup: {
                    from: "keywords",
                    localField: "keyword",
                    foreignField: "_id",
                    as: "keyword_refs"
                }
            },
            { $unwind: "$keyword_refs" },
            {
                $group: {
                    "_id": { "keyword": "$keyword", "website": "$website" },
                    "website": { "$first": "$website" },
                    "user": { "$first": "$user" },
                    "type": { "$first": "$type" },
                    "ranks": { "$push": { "createdDateStr": "$createdDateStr", "rank": "$rank" } },
                    "keyword_refs": { "$addToSet": "$keyword_refs" }
                }
            },
            { $limit: count },
            { $skip: skip }
        ]).allowDiskUse(true);

【讨论】：