Using $size aggregation in a transaction

[Robert Veres]

Hi, I'm new to KMongo and I would like to return number of elements in an Array in a specific document

something like this:

val result = chats.aggregate<Result>("[{\$match : {_id:'$chatId'}}, {\$project: { _id : 1, messageCount : {\$size: '\$messages'}}}]")

But, I need to do it in a transaction, because I use the result later.

But I can't find an aggregate function that would accept a ClientSession and a String. Only ClientSession and List<Bson>. Unfortunately from what I tried, it seems I can't use the size aggregation in Bson.

I'm probably overlooking something. Any ideas how can I do it?

Thank you

[zigzago]

Hello,

Look at https://litote.org/kmongo/dokka/kmongo/org.litote.kmongo/com.mongodb.client.-mongo-collection/index.html for extensions overview.

fun <TResult : Any> MongoCollection<*>.aggregate(clientSession: ClientSession, vararg pipeline: String): AggregateIterable<TResult>

seems to fill your need - each string is a stage representation.

HTH