My aggregation give me this results in mongodb query

{"_id" : 1, "color" : "red", "year" : 2019},
{"_id" : 2, "color" : "blue", "year" : 2018},
{"_id" : 3, "color" : "green", "year" : 2020}

and in php I have the results like this:

array(3) {
    [0] => array(3) {
        ["_id"] => int(1),
        ["color"] => string(3) "red"
        ["year"] => int(2019),
    },
    [1] => array(3) {
        ["_id"] => int(2),
        ["color"] => string(4) "blue"
        ["year"] => int(2018),
    },
    [2] => array(3) {
        ["_id"] => int(3),
        ["color"] => string(5) "green"
        ["year"] => int(2020),
    }
}

what I need is to have it like this:

array(3) {
    ["red"] => array(3) {
        ["_id"] => int(1),
        ["color"] => string(3) "red"
        ["year"] => int(2019),
    },
    ["blue"] => array(3) {
        ["_id"] => int(2),
        ["color"] => string(4) "blue"
        ["year"] => int(2018),
    },
    ["green"] => array(3) {
        ["_id"] => int(3),
        ["color"] => string(5) "green"
        ["year"] => int(2020),
    }
}

So in words, I want to return the documents results as an array with the key as the $color of each document. What I did is to loop one time throw the results and copy in a new array as follow:

newArray = [];

foreach($query as $doc){
    $newArray[$doc['color']] = $doc;
}

and now newArray have the structure I need but I want to achieve it directly from mongo so the php server side not have to do the work when there are thousand of documents.

CodePudding user response：

It sounds like adding these two steps to your aggregation can do the job:

{$group: {_id: 0, arr: {$push: {k: '$color', v: {_id: '$_id', color: '$color', 
    year: '$year'}}}}},
{$project: {res: {$arrayToObject: '$arr'}, _id: 0}}

Returning:

{
"res" : {
    "red" : {
        "_id" : 1,
        "color" : "red",
        "year" : 2019
    },
    "blue" : {
        "_id" : 2,
        "color" : "blue",
        "year" : 2018
    },
    "green" : {
        "_id" : 3,
        "color" : "green",
        "year" : 2020
    }
}
}