Elasticsearch Score Normalizer

Plugin to normalize score using Min Max or Z Score normalizer and updates normalized score by a given factor and factor_mode. This plugin is built on top of elasticsearch's rescorer feature and normalizes the top docs.

If page size is 10 and from offset is 20. Then all 30 docs will be normalized.

Common Attributes

normalizer_type (Optional)

Type of the normalizer. Accepts z_score or min_max, if nothing passed defaults to z_score.

factor (Optional)

A float value. If passed updates the normalized score using this factor and given operation (factor_mode)

factor_mode (Optional)

Tells how to combine normalized score and the factor. Accepted values are sum, multiply and increase_by_percent. increase_by_percent increases the score by given factor(values from 0 to 1)

Min Max Normalizer

Attributes

min_score - minimum score value of the returned top docs. Default is 1.

max_score - maximum score value of the returned top docs. Default is 5.

on_score_same - Normalize strategy when all docs score are same. Accepted values are avg (average of max and min), max(maximum value), min(minimum value)

Normalize scores between given max_score and min_score. If no min_score and max_score is passed, defaults to 1 and 5 respectively.

Example:

       
{
  "query": {
    ... some query
  },
  "from" : 0,
  "size" : 50,
  "rescore" : {
      "score_normalizer" : {
        "normalizer_type" : "min_max",
        "min_score" : 1,
        "max_score" : 10
      }
   }
}

Z Score Normalizer

Normalize scores using Z Score.

Below example first normalizes the scores using z-score and then increase the score by 60 percent. Example:

{
  "query": {
    ... some query
  },
  "from" : 0,
  "size" : 50,
  "rescore" : {
      "score_normalizer" : {
        "normalizer_type" : "z_score",
        "min_score" : 1,
        "factor" : 0.6,
        "factor_mode" : "increase_by_percent"
      }
   }
}

Installation

Change the elasticsearch version in pom.xml with your Elasticsearch server version. You can safely change the version between 7.0 to 7.12 without any code changes.
Build using: mvn clean install
Install the zip file generated in folder: <path to project>/project/target/releases/elasticsearch-score-normalizer-rescorer-1.0-SNAPSHOT.zip

To install, go to ES bin folder and type command:

./elasticsearch-plugin install file:<path to zip plugin>

License

The MIT License (MIT)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

bkatwal/elasticsearch-score-normalizer