I want to sort the Mongodb data based on Array size

I’m having student (String) and instructor (List of String).I want to fetch the record based on the instructor count in Descending order. instructor as below
Sample: [a,b,c] -3, [e,f] -2, [g,h,i,j] -4.

I want in the order of 4 and 3 and then 2.

That is based on the field instructor array’s size.How to query this using mongoTemplate or custom mongodb query or aggregation??

Answer

I have found a way to sort by array size from mongodb.
Aggregation for the above is:

newAggregation(addFields().addField(“nInstructors”)
.withValue(new Document (“$size, “nInstructors”)).build(),
sort(DESC, “nInstructors”),
limit(limitCount)
);