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Rank feature field type

A rank_feature field can index numbers so that they can later be used to boost documents in queries with a rank_feature query.

 PUT my-index-000001 { "mappings": { "properties": { "pagerank": { "type": "rank_feature" }, "url_length": { "type": "rank_feature", "positive_score_impact": false } } } } PUT my-index-000001/_doc/1 { "pagerank": 8, "url_length": 22 } GET my-index-000001/_search { "query": { "rank_feature": { "field": "pagerank" } } }
  1. Rank feature fields must use the rank_feature field type
  2. Rank features that correlate negatively with the score need to declare it
Note

rank_feature fields only support single-valued fields and strictly positive values. Multi-valued fields and negative values will be rejected.

Note

rank_feature fields do not support querying, sorting or aggregating. They may only be used within rank_feature queries.

Note

rank_feature fields only preserve 9 significant bits for the precision, which translates to a relative error of about 0.4%.

Rank features that correlate negatively with the score should set positive_score_impact to false (defaults to true). This will be used by the rank_feature query to modify the scoring formula in such a way that the score decreases with the value of the feature instead of increasing. For instance in web search, the url length is a commonly used feature which correlates negatively with scores.