elasticsearch - Why script in custom_filters_score behaves as boost? -

{   "query": {     "custom_filters_score": {       "query": {         "term": {           "name": "user1234"         }       },       "filters": [         {           "filter": {             "term": {               "subject": "math"             }           },           "script": "_score + doc['subject_score'].value"         }       ]     }   } } 

if script having above gives error: unresolvable property or identifier: _score if script "script": "doc['subject_score'].value" multiplies _score in similar way boost does. want replace elasticsearch _score custom score.

if understood correctly use elasticsearch scoring if subject not math , use custom scoring subject math. if using elasticsearch v0.90.4 or higher, can achieved using new function_score query:

{     "query": {         "function_score": {             "query": {                 "term": {                     "name": "user1234"                 }             },             "functions": [{                 "filter": {                     "term": {                         "subject": "math"                     }                 },                 "script_score": {                     "script": "doc[\"subject_score\"].value"                 }             }, {                 "boost_factor": 0              }],             "score_mode": "first",             "boost_mode": "sum"         }     } } 

prior v0.90.4 have resort using combination of custom_score , custom_filters_score:

{     "query": {         "custom_score": {             "query": {                 "custom_filters_score": {                     "query": {                         "term": {                             "name": "user1234"                         }                     },                     "filters": [{                         "filter": {                             "term": {                                 "subject": "math"                             }                         },                         "script": "-1.0"                     }]                 }             },             "script": "_score < 0.0 ? _score * -1.0 + doc[\"subject_score\"].value : _score"         }     } } 

or @javanna suggested, use multiple custom_score queries combined bool query:

{     "query": {         "bool": {             "disable_coord": true,             "should": [{                 "filtered": {                     "query": {                         "term": {                             "name": "user1234"                         }                     },                     "filter": {                         "bool": {                             "must_not": [{                                 "term": {                                     "subject": "math"                                 }                             }]                         }                     }                 }             }, {                 "filtered": {                     "query": {                         "custom_score": {                             "query": {                                 "term": {                                     "name": "user1234"                                 }                             },                             "script": "doc['subject_score'].value"                         }                     },                     "filter": {                         "term": {                             "subject": "math"                         }                     }                 }             }]         }     } }