Convert following MongoDB update statement to SpringBoot equivalent

Question

I am trying to remove an element from a list inside a document using the index as suggested here

db.example.update({}, [
     {$set:{ sequence: {
           $concatArrays:[ 
               {$slice:[ "$sequence", P ]}, 
               {$slice:[ "$sequence", {$add:[1,P]}, {$size:"$sequence"}]}
           ]
     }}}
]);

However, I am having problems while trying to convert the query to the spring syntax equivalent:

Update update = new Update();

/*how do I pass the slice in the following statement?*/
ArrayOperators.ConcatArrays array = ArrayOperators.ConcatArrays.arrayOf(****);
SetOperators.SetUnion setUnion = SetOperators.SetUnion.arrayAsSet(** slice with add and size***).union(array);
update.set("sequence", setUnion);

Thanks

Answer 1

The second parameter to $concatArrays should look something like this.

ArrayOperators.Slice.sliceArrayOf("sequence")
.offset(P+1)
.itemCount(ArrayOperators.Size.lengthOfArray("sequence"));

Unfortunately, itemCount accepts only int arguments, so this won't work.

If your array has distinct elements, you can try this modified query.

db.collection.update({},
[
  {
    "$set": {
      "sequence": {
        "$concatArrays": [
          {
            "$slice": ["$sequence",P]
          },
          {
            "$setDifference": [
              "$sequence",
              {
                "$slice": ["$sequence",{$add:[P,1]}]
              }
            ]
          }
        ]
      }
    }
  }
])

Demo

Since you need pipelined update, you need to use AggregationUpdate.

AggregationUpdate update = Aggregation.newUpdate()
    .set("sequence")
    .toValue(ArrayOperators.ConcatArrays
        .arrayOf(ArrayOperators.Slice.sliceArrayOf("sequence").itemCount(P))
        .concat(SetOperators.SetDifference.arrayAsSet("sequence")
            .differenceTo(ArrayOperators.Slice.sliceArrayOf("sequence").itemCount(P+1))));
        

---

Another easier way is to do this in javascript using $function

db.collection.update({},[
{
    $set: {
        "sequence": {
            $function: {
                body: function(sequence) {
                    sequence.splice(P,1);
                    return sequence;
                },
                args: ["$sequence"],
                lang: "js"
            }
        }
    }
}
]);

Demo

AggregationUpdate update = Aggregation.newUpdate()
    .set("sequence")
    .toValue(ScriptOperators
        .function("function(sequence) {\r\n" 
            + "  sequence.splice(P,1);\r\n"
            + "  return sequence;\r\n" 
            + "}")
        .args("$sequence")
        .lang("js"));