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shellmongodbtimestampunix-timestamp

How do I extract the created date out of a Mongo ObjectID

I'm using the Mongo shell to query my Mongo db. I want to use the timestamp contained in the ObjectID as part of my query and also as a column to extract into output. I have setup Mongo to create ObjectIDs on its own.

My problem is I can not find out how to work with the ObjectID to extract its timestamp.

Here are the queries I am trying to get working. The 'createdDate' field is a placeholder; not sure what the correct field is:

//Find everything created since 1/1/2011
db.myCollection.find({date: {$gt: new Date(2011,1,1)}});

//Find everything and return their createdDates
db.myCollection.find({},{createdDate:1});
Solution

  • getTimestamp()

    The function you need is this one, it's included for you already in the shell:

    ObjectId.prototype.getTimestamp = function() {
    return new Date(parseInt(this.toString().slice(0,8), 16)*1000);
}

    References

    Check out this section from the docs:

    This unit test also demostrates the same:

    Example using the Mongo shell:

    > db.col.insert( { name: "Foo" } );
> var doc = db.col.findOne( { name: "Foo" } );
> var timestamp = doc._id.getTimestamp();

> print(timestamp);
Wed Sep 07 2011 18:37:37 GMT+1000 (AUS Eastern Standard Time)

> printjson(timestamp);
ISODate("2011-09-07T08:37:37Z")