Mongodb:按数组对象对文档进行排序 [英] Mongodb: sort documents by array objects

问题描述

我想按包含最低 foo.bar 值(它们是数组对象)的排序顺序返回文档.

I would like to return the documents in an order sorted by which holds the lowest foo.bar value (which are array objects).

我可以执行 db.collection.find().sort({foo.0.bar: 1})，但这仅匹配数组中的第一个元素 - 正如您所见在下面的示例中，将首先对项目 1 进行排序(foo.0.bar = 5)，而我希望首先返回项目 2 (foo.2.bar = 4)，因为它具有对象最低值.

I can do db.collection.find().sort({foo.0.bar: 1}), but this only matches the first element in the array - and as you can see in the exampe below would sort item 1 first (foo.0.bar = 5), wheras I am looking to return item 2 first (foo.2.bar = 4) as it has the object with the lowest value.

{
    "name": "Item 1",
    "foo": [
        {
            "bar": 5
        },
        {
            "bar": 6
        },
        {
            "bar": 7
        }
    ]
}
{
    "name": "item 2",
    "foo": [
        {
            "bar": 6
        },
        {
            "bar": 5
        },
        {
            "bar": 4
        }
    ]
}

推荐答案

看来 mongo 可以做到这一点.

It seems mongo can do this.

例如，如果我有以下文件:

For example, if I have the following documents:

{ a:{ b:[ {c:1}, {c:5 } ] } }
{ a:{ b:[ {c:0}, {c:12} ] } }
{ a:{ b:[ {c:4}, {c:3 } ] } }
{ a:{ b:[ {c:1}, {c:9 } ] } }

然后运行以下命令:

db.collection.find({}).sort({ "a.b.c":1 });
// produces:
{ a:{ b:[ {c:0}, {c:12} ] } }
{ a:{ b:[ {c:1}, {c:5 } ] } }
{ a:{ b:[ {c:1}, {c:9 } ] } }
{ a:{ b:[ {c:4}, {c:3 } ] } }

db.collection.find({}).sort({ "a.b.c":-1 });
// produces:
{ a:{ b:[ {c:0}, {c:12} ] } }
{ a:{ b:[ {c:1}, {c:9 } ] } }
{ a:{ b:[ {c:1}, {c:5 } ] } }
{ a:{ b:[ {c:4}, {c:3 } ] } }

如您所见，{"abc":1} 排序采用数组中所有值的 min 并对其进行排序，而 sort by{"abc":-1} 取所有值的 ma​​x.

As you can see, the sort by {"a.b.c":1} takes the min of all values in the array and sorts on that, whereas the sort by {"a.b.c":-1} takes the max of all the values.

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