java 中的 Elasticsearch 条件评分

Question

I am new to Elastic Search and I wanted to ask how can I boost certain results from a query based on some conditional. Specifically, the items in Elastic Search are of the following format:

"name":"item1",
"desc":"desc1",
"brand":"brandname"

I want to make the score of certain items (those with "brand" = "nike" ) have lower score than the other brands. Is there a way to do that with the QueryBuilders classes that java has for elastic search?

Answer 1

Boosting query might be able to solve the problem. Alternatively, you can also use function_score queries for more flexibility.

Example with boosting query.

(1) Index few documents

curl -XPOST localhost:9200/idx/doc/1 -d '{"content": "foo"}' --header "Content-type:application/json" 
curl -XPOST localhost:9200/idx/doc/2 -d '{"content": "bar"}' --header "Content-type:application/json" 
curl -XPOST localhost:9200/idx/doc/3 -d '{"content": "foo fred bar"}' --header "Content-type:application/json" 

(2) Query with a negative boost for bar to reduce score for bar

 curl -XPOST localhost:9200/idx/_search?pretty -d '{
  "query": {
    "boosting": {
      "positive": {
        "match": {
          "content": "foo bar fred"
        }
      },
      "negative": {
        "match": {
          "content": "bar"
        }
      } , "negative_boost": 0.001
    }
  }
}' --header "Content-type:application/json" 


{
  "took" : 59,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 3,
      "relation" : "eq"
    },
    "max_score" : 0.5619609,
    "hits" : [
      {
        "_index" : "idx",
        "_type" : "doc",
        "_id" : "1",
        "_score" : 0.5619609,
        "_source" : {
          "content" : "foo"
        }
      },
      {
        "_index" : "idx",
        "_type" : "doc",
        "_id" : "3",
        "_score" : 0.0014472058,
        "_source" : {
          "content" : "foo fred bar"
        }
      },
      {
        "_index" : "idx",
        "_type" : "doc",
        "_id" : "2",
        "_score" : 5.619609E-4,
        "_source" : {
          "content" : "bar"
        }
      }
    ]
  }
}

Answer 2

To boost a certain value of a certain field (or vice versa), you can use a Function score query . Check the official document Here .

Let me show you an example:

    POST /goods/_search
    {
      "query": {
        "function_score": {
          "query": {
            "match": {
              "name": "shoes"
            }
          },
          "functions": [
            {
              "filter": {
                "term": {
                  "maker": "nike"
                }
              },
              "weight": 0
            }
          ],
          "boost_mode": "multiply"
        }
      },
      "sort": [
        {
          "_score": {
            "order": "desc"
          }
        }
      ]
    }

This query refers that "I'm looking for documents which match a keyword shoes in a name field and sort in reverse order of _score . If documents have a term nike in a maker field, however, I hope that the score is 0(cause multiplying any number by 0 equals 0)."

In Java code,

    String indexName = "goods"
    String nameField = "name";
    String makerField = "maker";

    String keyword = "shoes";
    String unnecessaryMaker = "nike";
    
    MatchQueryBuilder matchQueryBuilder = new MatchQueryBuilder(nameField, keyword);
    FilterFunctionBuilder[] filterFunctions = {
        new FunctionScoreQueryBuilder.FilterFunctionBuilder(
            QueryBuilders.termQuery(makerField, unnecessaryMaker),
            ScoreFunctionBuilders.weightFactorFunction(0)
        )
    };
            
    FunctionScoreQueryBuilder functionScoreQueryBuilder = QueryBuilders.functionScoreQuery(matchQueryBuilder, filterFunctions);
    functionScoreQueryBuilder.boostMode(CombineFunction.MULTIPLY);

    SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
    searchSourceBuilder.query(functionScoreQueryBuilder);
        
    SearchRequest request = new SearchRequest();
    request.indices(indexName);
    request.source(searchSourceBuilder);

There are several boost_mode such as multiply(default), replace, sum, avg, max, min. So you can apply this code to your needs.

Hope this is what you were looking for.