MongoDB Java - UpdateMany() 具有 $inc 运算符和 $concat 聚合

Question

JavaVersion: 11 --- MongoDB-driver: 4.6.1

I'm wondering if it is possible to implement a bulk update method that would increment the document version through the $inc operator while simultaneously making it possible to concatenate a string to a field value through $concat aggregation .

I've tried some workarounds, but I cannot manage the whole thing to work, in particular:

1. Combining all the operators in a single Bson with Updates::combine -> $concat and $inc works independently, but combining both of them I get this error: "A pipeline stage specification object must contain exactly one field."

2. Passing a List of Bson to "updateMany() -> I get no error, but $concat does not work as expected, in the DB I have something like:

    "field1": {"$concat": ["$field1", "_OK"]},

In order to make $concat work I use this (according to the documentation):

        Updates.set(new Document("$concat", Arrays.asList(
            new BsonString(String.format("$%s", key)),
            new BsonString(value))));

While for $inc I'm using the Updetes.inc() method.

////////////////////////////////////////////////////////////////////////////////////////////////////////////////

Here is the resulting Update object from the 1 and 2 strategies:

List of BSON

[
    Update
    {
        fieldName='field1',
        operator='$set',
        value=Document
            {
                {
                    $concat=
                        [
                            BsonString{value='$field1'},
                            BsonString{value='_OK'}
                        ]
                }
            }
    }, 
    Update
    {
        fieldName='field2',
        operator='$set',
        value=2022-08-29T14:16:07.931Z
    },
    Updates{
        updates=[
            Update
            {
                fieldName='documentId.version',
                operator='$inc',
                value=1
            }, 
            Update
            {
                fieldName='documentId.objId',
                operator='$set',
                value=c4c93c42-1007-4b86-85e4-a45396b9ba0c
            }, 
            Update
            {
                fieldName='updatedTimestamp',
                operator='$set',
                value=2022-08-29T14:16:07.931Z
            }
        ]
    }
]

Combining all the operands

Updates
{
    updates=
    [
        Updates
        {
            updates=
            [
                Update
                {
                    fieldName='field1',
                    operator='$set',
                    Document
                    {
                        {
                            $concat=
                            [
                                BsonString{value='$field1'},
                                BsonString{value='_OK'}
                            ]
                        }
                    }
                },
                Update
                {
                    fieldName='field2',
                    operator='$set',
                    value=2022-08-29T14:30:49.269Z
                }
            ]
        },
        Updates
        {
            updates=
            [
                Update
                {
                    fieldName='documentId.version',
                    operator='$inc',
                    value=1},
                Update
                {
                    fieldName='documentId.objId',
                    operator='$set',
                    value=cdf5f0b7-5832-40cc-88e5-a71172afa58a
                },
                Update
                {
                    fieldName='updatedTimestamp',
                    operator='$set',
                    value=2022-08-29T14:30:49.269Z
                }
            ]
        }
    ]
}

Answer 1

Solved

As pointed out by prasad_ in the comments, you can't combine update operators with pipeline ones. To solve the issue, I've used a List of BSON using $add aggregation instead of the $inc operator.

An implementation idea for the $add operator.

Updates.set(key, new Document("$add", Arrays.asList(
                new BsonString(key),
                value)));