迭代具有有限批量大小的 Mongo 游标

Question

如何遍历以下数据游标？以下代码给出错误“

TypeError: Object [object Object] has no method 'forEach'

var data = db.profiles.runCommand("aggregate", {
    pipeline: [
        {$limit: 100000},
        {$unwind: "$Items"},
        {   $group: {
                _id: "$Items", count: {$sum: 1}
            },
        },
    ],
    allowDiskUse: true,
    cursor: { batchSize: 100 }
});

data.forEach(printjson) // gives error

数据变量包含以下内容

MongoDB shell version: 2.6.5
connecting to: myCollection

    {
        "cursor" : {
            "id" : NumberLong("61248019114"),
            "ns" : "myCollection.profiles",
            "firstBatch" : [
                {
                    "_id" : "alex",
                    "count" : 1
                },
                {
                    "_id" : "james",
                    "count" : 1
                } .......
            },
        "ok" : 1
    }

Answer 1

编辑：

来自 MongoDB RunCommand Docs:

Using the aggregate command to return a cursor is a low-level operation, intended for authors of drivers. Most users should use the db.collection.aggregate() helper provided in the mongo shell or in their driver. In 2.6 and later, the aggregate() helper always returns a cursor.

您需要发送 OP_GET_MORE 消息来遍历光标。

改为使用 aggregate() helper。

var data= db.profiles.aggregate([
    {$limit: 100000},
        {$unwind: "$Items"},
        {   $group: {
                _id: "$Items", count: {$sum: 1}
            },
        },
    ],
    {
        allowDiskUse: true,
        cursor: { batchSize: 100}
    }
)

这returns你一个游标。您可以使用 forEach 方法对其进行迭代。

data.forEach(printjson)

迭代具有有限批量大小的 Mongo 游标

iterating over a Mongo Cursor with finite batch size

cursor

mongodb

mongodb-query