Query live data from large MongoDB collection - Nodejs - node.js

Question

I want to get last 10 records and newest record which just added.
I tried to use tailable cursor but it took me too much time because it have to scan entire collection before reach the end of collection to wait data.
{
"_id" : ObjectId("56fe349d0ef0edb520f0ca29"),
"topic" : "IoTeam/messages/",
"payload" : "20:15:04:01:12:75,-127.00,679",
"qos" : 0,
"retain" : false,
"_msgid" : "45975d0d.ba68a4",
"mac" : "20:15:04:01:12:75",
"temp" : "-127.00",
"hum" : "679",
"time" : "01/04/2016 15:43:09"
}
Thank for your help.

Answer 1

Still difficult to say the best solution without knowing more information. But here is one suggestion that you could try (all using the mongo shell)
Create an index on the time key.
db.your_collection_name.createIndex({time:-1})
After you have created the index, type the following to ensure it was done correctly.
db.your_collection_name.getIndexes()
This will list your indexes, and you should see that a new one was added for the time key.
Caution: Although this will reduce the amount of time it takes to query on the time key, it will increase the amount of time it takes to insert new records into your database. This is due to the fact that new inserts will need to be indexed. So take that into consideration when scaling your app, and it may mean down the road you will want to handle this in a different way.

Answer 2

First of all, create an index on the field time.
db.collection('nameOfYourCollection')
.createIndex(
{ "time": -1 },
null,
function(err, results){
console.log(results);
});
This will create an index on the time field of your collection. This might take some time. But once the index is created, the queries will be much faster.
After this in your query just do this :
var cursor = db.collection('nameOfYourCollection').find().sort([ ["time", -1] ]).limit(10);
cursor.forEach(function(doc){
if(doc) console.log("Got the document as : " + JSON.stringify(doc));
}, function(err){
if(err) console.log("Error: " + JSON.stringify(err));
});
This will give you the last 10 records that were inserted in the collection.
You can also call toArray instead of forEach in the cursor. Something like this :
var cursor = db.collection('nameOfYourCollection').find().sort([ ["time", -1] ]).limit(10);
cursor.toArray(function(err, docs){
if(err) console.log("Error: " + JSON.stringify(err));
if(docs){
console.log("Got the document as : " + JSON.stringify(docs));
console.log("This is the latest record that was inserted : " + JSON.stringify(docs[0]));
}
});
Hope this helps.