Call a Mongo function from aggregation pipeline through JAVA Driver API-CodePudding

I am able to get the following working in mongosh

var pipeline = [
    { $group: { _id: "$column1", valArray: { $push: "$column2" } } },
    { $set: {
            val: function1("$valArray", 70)    
        }
    },
    { $unset: [ "valArray" ] },
    { $sort: { _id: 1 } }
];

function1 is function defined to take an array and a number as param

When I try the same with Java I get the error while trying to create List

List<Bson> pipeline = Stream.of(new String[] {
    "{ $group: { _id: \"$column1\", valArray: { $push: \"$column2\" } } }",
    "{ $set: { percentile_n: function1(\"$valArray\", "   percentileN   ") } }",
    "{ $unset: [ \"valArray\" ] }",
    "{ $sort: { _id: 1 } }"
  })
  .map(s -> Document.parse(s).toBsonDocument())
  .collect(Collectors.toList());


Exception in thread "main" org.bson.json.JsonParseException: **JSON reader was expecting a value but found 'function1'**.
    at org.bson.json.JsonReader.readBsonType(JsonReader.java:263)
    at org.bson.codecs.DocumentCodec.decode(DocumentCodec.java:175)
    at org.bson.codecs.DocumentCodec.decode(DocumentCodec.java:44)
    at org.bson.internal.LazyCodec.decode(LazyCodec.java:48)
    at org.bson.codecs.ContainerCodecHelper.readValue(ContainerCodecHelper.java:61)
    at org.bson.codecs.DocumentCodec.decode(DocumentCodec.java:177)
    at org.bson.codecs.DocumentCodec.decode(DocumentCodec.java:44)
    at org.bson.Document.parse(Document.java:126)
    at org.bson.Document.parse(Document.java:111)

Looks like there is a specific way to create BsonDocument for a function call. Can anyone please help?

CodePudding user response：

Seems like Mongo does not facilitate execution of functions on server from API. Only through mongo shell is this allowed.

CodePudding user response：

I would suggest you use $function. You can find some references in the documentation.

I just tried the following over a sample dataset and it works.

db.getCollection('projects').aggregate([ 
  { $group: { _id: "$status", count: { $count: {} }, packages: { $push: "$packageSlip" } } }, 
  { $set: { val: { $function: { 
      body: function(currentDaysLeft, extraDays){ return currentDaysLeft   extraDays}, 
      args: ['$daysLeft', 70], 
      lang: "js" } } } }
])

Good Luck