Mongodb Mapreduce giving an error

问题

I have a set of data in mapreduce.. 1000000 records for random formdata collected.. The data structure is as follows :

    { "_id" : ObjectId("4d9c8318cbb7813ef940d9e6"), "clientid" : 5, "FormData" : { "emailadress" : "SWV" } }
{ "_id" : ObjectId("4d9c8318cbb7813efb40d9e6"), "clientid" : 4, "FormData" : { "key1" : "VCYU", "key" : "PJO" } }
{ "_id" : ObjectId("4d9c8318cbb7813efc40d9e6"), "clientid" : 4, "FormData" : { "key1" : "NJ", "key" : "BZ" } }
{ "_id" : ObjectId("4d9c8318cbb7813efd40d9e6"), "clientid" : 2, "FormData" : { "last" : "AY", "first" : "B" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0041d9e6"), "clientid" : 4, "FormData" : { "key1" : "X", "key" : "QPIQ" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0241d9e6"), "clientid" : 5, "FormData" : { "emailadress" : "K" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0341d9e6"), "clientid" : 2, "FormData" : { "last" : "EJ", "first" : "K" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0441d9e6"), "clientid" : 5, "FormData" : { "emailadress" : "X" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0541d9e6"), "clientid" : 2, "FormData" : { "last" : "B", "first" : "G" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0641d9e6"), "clientid" : 4, "FormData" : { "key1" : "BWUE", "key" : "UJ" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0741d9e6"), "clientid" : 2, "FormData" : { "last" : "Q", "first" : "K" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0941d9e6"), "clientid" : 5, "FormData" : { "emailadress" : "IRH" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0b41d9e6"), "clientid" : 5, "FormData" : { "emailadress" : "VCMYE" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0c41d9e6"), "clientid" : 2, "FormData" : { "last" : "LZ", "first" : "L" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0d41d9e6"), "clientid" : 2, "FormData" : { "last" : "X", "first" : "YS" } }
{ "_id" : ObjectId("4d9c8318cbb7813e0e41d9e6"), "clientid" : 2, "FormData" : { "last" : "IA", "first" : "QT" } }
{ "_id" : ObjectId("4d9c8318cbb7813e1041d9e6"), "clientid" : 2, "FormData" : { "last" : "GZ", "first" : "MM" } }
{ "_id" : ObjectId("4d9c8318cbb7813e1141d9e6"), "clientid" : 3, "FormData" : { "phonenumber" : "G", "userid" : "KU", "key" : "KQ" } }
{ "_id" : ObjectId("4d9c8318cbb7813e1241d9e6"), "clientid" : 3, "FormData" : { "phonenumber" : "E", "userid" : "NU", "key" : "ZHP" } }
{ "_id" : ObjectId("4d9c8318cbb7813e1341d9e6"), "clientid" : 4, "FormData" : { "key1" : "FUYV", "key" : "GZ" } }

My map function is

function () {
    this.FormData.forEach(function (z) {emit(this.clientid, {count:1, datalength:1});});
}

My reduce function is :

function (key, vals) {
    var result = {count:0, datalength:0};
    vals.forEach(function (value) {result.count += value.count;result.datalength = value.datalength;});
    return result;
}

When i run db.clientdata.mapReduct(m,m2) i get

Wed Apr  6 15:09:35 uncaught exception: map reduce failed: {
    "assertion" : "map invoke failed: JS Error: TypeError: this.FormData.forEach is not a function nofile_b:1",
    "assertionCode" : 9014,
    "errmsg" : "db assertion failure",
    "ok" : 0
}

Can anyone please help?

Thanks in advance

回答1:

Why are you using count and datalength if they have the same value? Seems like you just need to use count.

Map Function:

function () {
   emit(this.clientid, {count:1});
}

Reduce Function:

function (key, vals) {
    var result = {count:0};
    vals.forEach(function (value) {result.count += value.count;});
    return result;
}

回答2:

forEach() is a method of Array, not any arbitrary object literal. You cannot use it to iterate over object properties.

来源：https://stackoverflow.com/questions/5571980/mongodb-mapreduce-giving-an-error

标签

mongodb

MapReduce