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Hot to get last 30 records of collection result in mongodb, but not from zero?

Question:

I try to make this with .sort({_id:1}).limit(30) but in result they are showing from 0 to 30, but not from 40 to 70 (for example), that's mean i see all messages to 30, and newer than 30 - not showing. How i can find out actually 30 messages from db.collection('messages') ?

Answer1:

You can set the first document to be included in the results by calling <a href="http://mongodb.github.io/node-mongodb-native/2.0/api/Cursor.html#skip" rel="nofollow">skip()</a> on the cursor:

.sort({_id: 1}).skip(40).limit(30)

Would provide the 41 through 70 documents after sorting by _id.

If you want to get the <em>last</em> 30 while keeping them in ascending order, reverse your sort, and then reverse the results using <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reverse" rel="nofollow">Array#reverse</a>:

coll.find().sort({_id: -1}).limit(30).toArray((err, docs) => { docs.reverse(); });

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