Mongodb: How to Get Timestamp and Objectid from Newest Document in Collection?
I Would Like to Get Last Created Documents in Collection and Return Their objectID and Timestamps. for Example If Yesterday I Created 10 Documents I Would Like...
I would like to get last created documents in collection and return their objectID and timestamps. For example if yesterday I created 10 documents I would like to return them with db.collection and then
const lastTimeStamp = will be the timestamp from the last created element
const lastTimeStampArray = will be array of timestamps from yesterdays records
const lastObjectId = will be ObjectID of last created document
const lastObjectIdsArray = array of last objectIds
I am using:
2 Answers
MongoDB's _id field has info about date stored in itself. The timestamp is contained in the first 4 bytes of a mongoDB id.
- You can use ObjectId.getTimestamp() function to get time from
_idof a document. - Sorting on an _id field that stores ObjectId values is roughly equivalent to sorting by creation time.
For you question:
// To get lastTimeStamp
db.collection.find().sort({ '_id': -1}).limit(1).forEach(
function(doc){
lastTimeStamp = doc._id.getTimestamp();
}
)
// to get lastObjectId
db.collection.find().sort({ '_id': -1}).limit(1).forEach(
function(doc){
lastObjectId = doc._id;
}
)
Now, to get all records inserted yesterday might be a bit of hard work. You need to extract all records inserted yesterday and from that you need to extract information you need.
// to get lastTimeStampArray and lastObjectIdsArray
var yesterdayStart = new Date();
yesterdayStart.setDate(yesterdayStart.getDate() - 1);
yesterdayStart.setHours(0,0,0,0);
var startId = Math.floor(yesterdayStart.getTime() / 1000).toString(16) + "0000000000000000";
var yesterdayEnd = new Date();
yesterdayEnd.setDate(yesterdayEnd.getDate() - 1);
yesterdayEnd.setHours(23,59,59,999);
var endId = Math.floor(yesterdayEnd.getTime() / 1000).toString(16) + "0000000000000000";
var lastTimeStampArray = [];
var lastObjectIdsArray = [];
db.collection("records")
.find( { _id: {
$gte: ObjectId(startId),
$lte: ObjectId(endId)
}
}
).forEach(
function(doc){
lastObjectIdsArray.push(doc._id);
lastTimeStampArray.push(doc._id.getTimestamp());
});
These are mongo shell commands you can write your node.js accordingly.
You can get last inserted record with timestamp using the following:
db.collection.find().sort({ '_id': -1 }).limit(1).forEach(
function(doc){
print("record:"+doc._id.getTimestamp());
})
_id is the Mongodb objectID
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