Boost values in query or in mapping

Question

I can send boost value with query like

{
  "query": {
    "bool": {
      "should": [
        {
          "match": {
            "title": {
              "query": "quick brown fox",
              "boost": 2 
            }
          }
        }
      ]
    }
  }
}

but I can also set boost value in mapping

{
  "properties": {
    "title": {
      "type": "string",
      "boost": 2
    },
    "tags": {
      "type": "string"
    }
  }
}

And my question is. Which of this is faster while executing queries, to have boost in mapping or setting boost in query, or is it equaly fast.

As it relies on lucene you can check the analogous question for solr => [Solr Index time boosting VS Query time boosting?](http://stackoverflow.com/questions/10529127/solr-index-time-boosting-vs-query-time-boosting). — moliware, Jul 24 '15 at 13:39

score 1 · Accepted Answer · answered Jul 24 '15 at 13:33

Index-time boosting is unrecommended by Elastic itself for multiple reasons :

Combining the boost with the field-length norm and storing it in a single byte means that the field-length norm loses precision. The result is that Elasticsearch is unable to distinguish between a field containing three words and a field containing five words.
To change an index-time boost, you have to reindex all your documents. A query-time boost, on the other hand, can be changed with every query.
If a field with an index-time boost has multiple values, the boost is multiplied by itself for every value, dramatically increasing the weight for that field.

See https://www.elastic.co/guide/en/elasticsearch/guide/current/practical-scoring-function.html for more details.

As for speed, I don't think it changes much at all, so you should probably stick to Query-time boosting which is the norm.

Boost values in query or in mapping

1 Answers1