javascriptmongodb

Can I query MongoDB ObjectId by date?


I know that ObjectIds contain the date they were created on. Is there a way to query this aspect of the ObjectId?


Solution

  • Popping Timestamps into ObjectIds covers queries based on dates embedded in the ObjectId in great detail.

    Briefly in JavaScript code:

    /* This function returns an ObjectId embedded with a given datetime */
    /* Accepts both Date object and string input */
    
    function objectIdWithTimestamp(timestamp) {
        /* Convert string date to Date object (otherwise assume timestamp is a date) */
        if (typeof(timestamp) == 'string') {
            timestamp = new Date(timestamp);
        }
    
        /* Convert date object to hex seconds since Unix epoch */
        var hexSeconds = Math.floor(timestamp/1000).toString(16);
    
        /* Create an ObjectId with that hex timestamp */
        var constructedObjectId = ObjectId(hexSeconds + "0000000000000000");
    
        return constructedObjectId
    }
    
    
    /* Find all documents created after midnight on May 25th, 1980 */
    db.mycollection.find({ _id: { $gt: objectIdWithTimestamp('1980/05/25') } });