Elasticsearch: 'x_content_parse_exception', [bool] failed to parse field [must]

Question

I am getting the error:

BadRequestError(400, 'x_content_parse_exception', '[1:34] [bool] failed to parse field [must]')

following is my source code:

query ={
  
   "size":50,
   "_source": "Title", 
   "query":{
      "bool":{
         "must":[
            {
               "knn":{
                  "vectors":{
                     "vector":token_vector,
                     "k":20
                  }
               }
            }
         ]
      }
   }
}

res = es.search(index='posting', body=query)

I am using the latest version of elasticsearch (8.5.2)

I also searched for similar questions raised before but unfortunately, I could not get any answers satisfying my question.

Answer 1

Knn is parameter search query. Try like this

{
   "size":50,
   "_source":"Title",
   "query":{
      "bool":{
         "must":[
            //other clausule
         ]
      }
   },
   "knn":{
     "field": "FIELD_VECTOR",
     "query_vector": "YOUR_VECTOR",
     "k": 10,
     "num_candidates": 100
   }
}