How to find longest and shortest length of a value for a field in mongoDb?

The data type of the field is String. I would like to find the length of the longest and shortest value for a field in mongoDB.

I have totally 500000 documents in my collection.

You can use a mongo shell script. Note that it will perform a full table scan.

    function findMinMax() {
        var max = 0;
        var min = db.collection.findOne().fieldName.length;

        db.collection.find().forEach(function(doc) {
            var currentLength = doc.fieldName.length; 
            if (currentLength > max) {
               max = currentLength;
            }
            if (currentLength < min) {
               min = currentLength;
            }
        });

         print(max);
         print(min);
    }

   use <databaseName>
   findMinMax();

You can save the function in a file say c:\minMax.js and run the file as,

c:\mongodb\bin> mongo dbName < c:\minMax.js

Note: you may need to supply the necessary hostname, user name, password to connect to your database.

c:\mongodb\bin> mongo --host hostName --port portNumber -u userName -p password dbName < c:\minMax.js