Filter elasticsearch results to contain only unique documents based on one field value

Question

All my documents have a uid field with an ID that links the document to a user. There are multiple documents with the same uid.

I want to p

Answer 1

You need a top_hits aggregation.

And for your specific case:

{
  "query": {
    "multi_match": {
      ...
    }
  },
  "aggs": {
    "top-uids": {
      "terms": {
        "field": "uid"
      },
      "aggs": {
        "top_uids_hits": {
          "top_hits": {
            "sort": [
              {
                "_score": {
                  "order": "desc"
                }
              }
            ],
            "size": 1
          }
        }
      }
    }
  }
}

The query above does perform your multi_match query and aggregates the results based on uid. For each uid bucket it returns only one result, but after all the documents in the bucket were sorted based on _score in descendant order.