mongodb數(shù)組字段prefix匹配返回

魏明發(fā)布于2019-06-26 17:57 / 967人閱讀

摘要：結(jié)構(gòu)對(duì)表的所有數(shù)據(jù)做過(guò)濾，返回中以開(kāi)頭的元素表原數(shù)據(jù)返回?cái)?shù)據(jù)示例數(shù)據(jù)庫(kù)隨機(jī)構(gòu)建表返回只保留了符合過(guò)濾規(guī)則的第一個(gè)元素，順序不能換返回將一個(gè)文檔拆分成多個(gè)文檔返回?cái)?shù)組元素包含字符串返回

DOC: https://docs.mongodb.com/manu...

collection（test）結(jié)構(gòu)

{
    _id: Objectd("123456789"),
    category: [
        "apple_1",
        "apple_2",
        "banana_1",
        "banana_2"
    ]
}

Question:

對(duì)test表的所有數(shù)據(jù)做category過(guò)濾，返回category中以apple開(kāi)頭的元素

表原數(shù)據(jù)：

[    
    {
        _id: Objectd("id1"),
        category: [
            "apple_1",
            "apple_2",
            "banana_1",
            "banana_2"
        ]
    },
    {
        _id: Objectd("id2"),
        category: [
            "apple_3",
            "apple_4",
            "banana_1",
            "banana_2"
        ]
    }
    ...
]

返回?cái)?shù)據(jù)示例：

[    
    {
        _id: Objectd("id1"),
        category: [
            "apple_1",
            "apple_2"
        ]
    },
    {
        _id: Objectd("id2"),
        category: [
            "apple_3",
            "apple_4"
        ]
    }
    ...
]

數(shù)據(jù)庫(kù)try：隨機(jī)構(gòu)建test表

function getRandomArrayElements(arr, count) {
    var shuffled = arr.slice(0), i = arr.length, min = i - count, temp, index;
    while (i-- > min) {
        index = Math.floor((i + 1) * Math.random());
        temp = shuffled[index];
        shuffled[index] = shuffled[i];
        shuffled[i] = temp;
    }
    return shuffled.slice(min);
}
var temp = ["apple_1","apple_2","banana_3","banana_4","pear_5","pear_6","pear_7"];
for(var i =0; i < 10; i ++){
    db.getCollection("test").insert({
            category:getRandomArrayElements(temp, Math.random()*7)
    })
}

Try 1:

db.test.find({},{"category":{
    "$elemMatch":{
        $regex: "apple"
    }
}})

[    
    {
        _id: Objectd("id1"),
        category: [
            "apple_1",
        ]
    },
    {
        _id: Objectd("id2"),
        category: [
            "apple_3",
        ]
    }
    ...
]

category只保留了符合過(guò)濾規(guī)則的第一個(gè)元素

Try 2:

db.test.aggregate(
    {
        $unwind: "$category"
    },
    {
        $match: {
            category: {
             $regex: "apple_"
            }
        }
    },
    //unwind，match順序不能換
)

[    
    {
        _id: Objectd("id1"),
        category: "apple_1"
    },
    {
        _id: Objectd("id1"),
        category: "apple_2"
    },
    {
        _id: Objectd("id2"),
        category: "apple_3"
    },
    {
        _id: Objectd("id2"),
        category: "apple_4"
    }
    ...
]

將一個(gè)文檔拆分成多個(gè)文檔返回

Try 3（Solution）:

db.test.aggregate({
    $project: {
        "category":{
            $filter: {
                input: "$category",
                as: "cate",
                cond: {
                    // category數(shù)組元素cate包含字符串"apple_"
                    $eq: [ {
                        $indexOfCP: ["$$cate", "apple_"]
                    }, 0] 
                }
            }
        }
    }
})

[    
    {
        _id: Objectd("id1"),
        category: [
            "apple_1",
            "apple_2"
        ]
    },
    {
        _id: Objectd("id2"),
        category: [
            "apple_3",
            "apple_4"
        ]
    }
    ...
]