elasticsearch - Error:Class cast exception in elastic search while sorting buckets in aggregation -

error: classcastexception[org.elasticsearch.search. aggregations.support.valuessource$bytes$withordinals$fielddata cannot cast org.elasticsearch.search.aggregations.support.valuessource$numeric]}{[vthdfzputegmgr8mes_b9g]

my query:

         _search {   "size" : 0,   "query" : {     "filtered" : {       "query" : {         "dis_max" : {           "tie_breaker" : 0.7,           "queries" : [ {             "bool" : {               "should" : [ {                 "match" : {                   "post.body" : {                     "query" : "check",                     "type" : "boolean"                   }                 }               }, {                 "match" : {                   "post.parentbody" : {                     "query" : "check",                     "type" : "boolean",                     "boost" : 2.0                   }                 }               } ]             }           } ]         }         }         }         },   "aggregations" : {     "by_parent_id" : {       "terms" : {         "field" : "post.parentid",         "order" : {           "max_score" : "desc"         }       },       "aggregations" : {         "max_score" : {           "max" : {}         },         "top_post" : {           "top_hits" : {             "size" : 1           }           }         }     }   } 

i want sort buckets max_score rather doc_count default behaviour of elastic search. trying aggregate posts (which contains body , parentbody) parentid , sorting buckets max_score , in each bucket getting top_hits. getting above error when sorted buckets defining max score aggregation. rest works if remove max_score aggregation. every post object has parentid, body , parentbody. have used following references coding this:

elasticsearch aggregation: how sort bucket order https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-metrics-top-hits-aggregation.html#_field_collapse_example

tell me doing wrong? have shared query above.