How to use Size class of ArrayOperation for Aggregation in Spring data Mongodb?

Question

{
"_id" : ObjectId("5b4d975be2194da53a85e69f"),
"ISBN" : 2,
"book_title" : "ZERO TO ONE",
"author_name" : "Peter Theil",
"publisher" : "Penguin",
"status" : "ISSUED",
"issued" : [
    {
        "member_name" : "suresh",
        "member_id" : 101,
        "from_date" : "1/01/2018",
        "to_date" : "15/02/2018"
    },
    {
        "member_name" : "Jay",
        "member_id" : 103,
        "from_date" : "16/02/2018",
        "to_date" : "30/03/2018"
    }
]}

This is my Mongodb Document format.What i want to do is Count array length of issued of each document. So my Output will be Count:2 for this document. I want to implement this with spring data mongodb. I referred there documentation and found there is a Size class for this in ArrayOperators class Link here:

Spring data mongodb Documentaion

But i am don't know Use Size class ???

Mongodb terminal query is:

    db.library.aggregate([{$project:{count:{$size:"$issued"},"book_title":1,"_id":0}])

s7vr · Accepted Answer · 2018-07-17 13:12:07Z

3

You can try below aggregation.

Using ArrayOperators

ProjectionOperation project = Aggregation.
            project("book_title").  
            andExclude("_id").
            and(ArrayOperators.arrayOf("issued").length()).as("count");

Using size helper method

ProjectionOperation project = Aggregation.
            project("book_title").
            andExclude("_id").
            and("issued").size().as("count");

Rest of aggregation

Aggregation aggregation = Aggregation.newAggregation(project);
List<Document> results = mongoTemplate.aggregate(aggregation, "library", Document.class).getMappedResults();

edited Jul 17, 2018 at 13:12

answered Jul 17, 2018 at 12:50

s7vr

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