nodejs和MongoDB的collection.find（）不响应

Question

I have about 30,000 documents in a MongoDB collection. And have been stuck in developing a node.js script to retrieve only the records with a specific string key-value pair.

this query on MongoDB server returns me the exact results I've been looking for:

db.getCollection('posts').find({authorName: "Ashwin-kumar"})

Returns me about 33 documents instantly. Likewise I've about 40 authors with different names.

Here's my node.js script to retrieve posts by authorName (Yes, it is based on Name, a string, as there is no ID for these authors :( ):

var fs = require('fs'),
    request = require('request'),
    async = require("async"),
    assert = require('assert');
    _ = require('lodash'),
    MongoClient = require('mongodb').MongoClient;

var db, postsCollection, postCol;

async.series([dbConnect, checkCollection, createMeta, dbClose], function(){
    console.log("Executed all calls in series.");
    process.exit(0);
});

function dbConnect(callback){
    MongoClient.connect("mongodb://localhost:27017/jPosts", function(pErr, pDb) {
        if(pErr) {
            console.dir(pDb);
            return 0;
        }
        db = pDb;
        callback();
    });
}

function dbClose(callback){
    db.close(true, function (err) {
        if (err) console.error(err);
        else console.log("close complete");
        callback();
    });
}

function checkCollection(callback) {
    db.collection('posts', function(err, collection) {});
    postsCollection = db.collection('posts');
    postCol = db.collection('posts');
    callback();
}

function createMeta(callback){
    var meta = [];
    postsCollection.aggregate([
        {
            $group : {_id : "$authorName"}
        }]).toArray(function(err, result) {
            assert.equal(err, null);
            async.forEachLimit(result, 1, function(pPost, callback) {
                getPosts(pPost._id, callback);
            }, function(err) {
                console.log(err);
                callback();
            });                
        });
}

function getPosts(pAuthor, callback){
    var cursor = postCol.find({ "authorName": pAuthor});
    cursor.toArray(function(err,items){
        if(err)
            callback(err);
           else
           callback(null, items);
        });
}

This does not seem to work for me. cursor.toArray() does nothing but wait forever. Is it because of too many fields in each document?

I tried to get the count of the documents the cursor fetched and it works well.

function getPosts(pAuthor, callback){
    var cursor = postCol.find({ "authourName": pAuthor});
    cursor.count().then(function(items_count) {
        console.log(items_count);
        callback();
    });        
}

Also, I tried the cursor's .each method to iterate the documents fetched. But no luck yet.

function getPosts(pAuthor, callback){
    var cursor = postCol.find({ "authourName": pAuthor});
    cursor.each(function(err, doc) {
        assert.equal(err, null);
       if (doc != null) {
          console.dir(doc);
       } else {
           console.log(err);
       }  
   });
}

Am I missing something here? What else can be done to make this work? Is there any issues with the way I'm using async?

PS: The idea here is to query the dump and generate the PDF's for authours in the jPost collection.

PS 2: Here's a sample document

{
    "_id" : ObjectId("571d36b55672f713fe346a66"),
    "id" : 56517,
    "authorName" : "Ashwin-kumar",
    "comment_count" : 380,
    "tagline" : "... Opinions you don't really need",
    "vote_count" : 5152,
    "exclusive" : null,
    "post": [
    ],
    "post_comments" : [ 
        //comment_count objects
    ],
    "date" : "2016-03-27"
}

(I've omitted post & post_comments parts for brevity.)

Answer 1

try this:

var collection = db.collection("collection_name");
collection.find({authourName: "Ashwin-kumar"}).toArray(function (err,items) {
     if (err) {
        console.dir(err);
     } else {
        //do something with items array
        console.dir(items);
     }
});

Answer 2

Did you check what is the value of pAuthor in getPosts? Because when you do aggregation, you receive a collection of objects with _id field (not authourName), so you should do:

// not sure why you need meta array, at least it's not used in the code you provided
meta.push({
   author: pPost._id
});
getPosts(pPost._id, callback);