Unable to combine "bool" query with "knn" query - Elastisearch

Question

I am trying to frame an ElasticSearch query to fetch some results from my index for a search engine project. I am using pproximate KNN for the same. Now, I have a couple of conditions that I want to add to my KNN query but it doesn't seem to be working as expected.

Here is a sample of my full query.

{
    "_source": {
        "includes": [
            "id",
            "name"
        ]
    },
    "from": 0,
    "size": 60,
    "query": {
        "bool": {
            "must_not": [
                {
                    "term": {
                        "id": 12345
                    } 
                }
            ]
        }
    },
    "knn": {
        "field": "text_embedding.predicted_value",
        "k": 100,
        "num_candidates": 300,
        "query_vector_builder": {
            "text_embedding": {
                "model_id": "sentence-transformers__all-minilm-l6-v2",
                "model_text": "Loreum Epsom"
            }
        }
    }
}

...the "id" field is mapped as an 'integer' in my elasticsearch Index. It was expected that the results must not include the _doc with "id" = 12345 but it returns the _doc with that "id". what's wrong?

Answer 1

If you want to exclude a specific set of documents, you need to use a filtered knn query (available since ES 8.4):

{
  "_source": {
    "includes": [
      "id",
      "name"
    ]
  },
  "from": 0,
  "size": 60,
  "knn": {
    "field": "text_embedding.predicted_value",
    "k": 100,
    "num_candidates": 300,
    "query_vector_builder": {
      "text_embedding": {
        "model_id": "sentence-transformers__all-minilm-l6-v2",
        "model_text": "Loreum Epsom"
      }
    },
    "filter": {                <--- add your filter here
      "bool": {
        "must_not": [
          {
            "term": {
              "id": 12345
            }
          }
        ]
      }
    }
  }
}