Spring Data MongoTemplate aggregation error 'input to $filter must be an array not object'

Question

I have a document structure like this:

{
    "_id" : ObjectId("...."),
    "oneMoreId" : "....",
    "items" : [
            {
                    "itemId" : "...",
                    "type" : "Food",
            }
    ]        
}

When I run JSON query in mongodb:

db.inventory.aggregate([
{$match: { $and: [{"oneMoreId":"..."},{"items.type": "Food"}]}},
{"$project": {
"oneMoreId": 1,
"items": {
    "$filter": {
        "input": "$items",
        "as": "item",
        "cond": {
            "$eq": ["$$item.type", "Food"]
        }
    }
}
}}
])

It works perfectly fine.

But when I use Spring Data's MongoTemplate to run aggregation, It throws me

input to $filter must be an array not object

This is my aggregation query (just the projection part):

ProjectionOperation projection = project("oneMoreId").and(new AggregationExpression() {

@Override
public Document toDocument(AggregationOperationContext context) {
    return new Document("$filter", new Document(
                  "input", "$items")
                  .append("as","item")
                  .append("cond", new Document("$eq", Arrays.asList("$$item.type","Food")))
              );
}
}).as("items");

I print it out in console and query is exactly the same as JSON query above. Exact. I have even tried pure Spring data's query:

ProjectionOperation projection = project("oneMoreId")
    .and(filter("items")
            .as("item")
            .by(valueOf("item.type")
                    .equalToValue("Food"))).as("items");

Again, same error (even though printing it results in the same exact JSON query above). The java object that holds items was a List. I changed it to just array Item [], and it still didn't work.

Any help would be greatly appreciated.

Faraz · Accepted Answer · 2018-09-29 23:10:30Z

1

Nevermind,

Someone (me) put in one Item by mistake in the form of an object instead of an array. That messed up everything. Just deleted that whole record and everything is normal.

answered Sep 29, 2018 at 23:10

Faraz

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1 Comment

PineCone Over a year ago

You would rather want to have an if not array check in your code than deleting bad data.

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