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- [[mapping-boost]]
- === `boost`
- Individual fields can be _boosted_ automatically -- count more towards the relevance score
- -- at query time, with the `boost` parameter as follows:
- [source,js]
- --------------------------------------------------
- PUT my_index
- {
- "mappings": {
- "my_type": {
- "properties": {
- "title": {
- "type": "text",
- "boost": 2 <1>
- },
- "content": {
- "type": "text"
- }
- }
- }
- }
- }
- --------------------------------------------------
- // AUTOSENSE
- <1> Matches on the `title` field will have twice the weight as those on the
- `content` field, which has the default `boost` of `1.0`.
- NOTE: The boost is applied only for term queries (prefix, range and fuzzy queries are not _boosted_).
- You can achieve the same effect by using the boost parameter directly in the query, for instance the following query (with field time boost):
- [source,js]
- --------------------------------------------------
- POST _search
- {
- "query": {
- "match" : {
- "title": {
- "query": "quick brown fox"
- }
- }
- }
- }
- --------------------------------------------------
- // AUTOSENSE
- is equivalent to:
- [source,js]
- --------------------------------------------------
- POST _search
- {
- "query": {
- "match" : {
- "title": {
- "query": "quick brown fox",
- "boost": 2
- }
- }
- }
- }
- --------------------------------------------------
- // AUTOSENSE
- The boost is also applied when it is copied with the
- value in the <<mapping-all-field,`_all`>> field. This means that, when
- querying the `_all` field, words that originated from the `title` field will
- have a higher score than words that originated in the `content` field.
- This functionality comes at a cost: queries on the `_all` field are slower
- when field boosting is used.
- deprecated[5.0.0, index time boost is deprecated. Instead, the field mapping boost is applied at query time. For indices created before 5.0.0 the boost will still be applied at index time.]
- [WARNING]
- .Why index time boosting is a bad idea
- ==================================================
- We advise against using index time boosting for the following reasons:
- * You cannot change index-time `boost` values without reindexing all of your
- documents.
- * Every query supports query-time boosting which achieves the same effect. The
- difference is that you can tweak the `boost` value without having to reindex.
- * Index-time boosts are stored as part of the <<norms,`norm`>>, which is only one
- byte. This reduces the resolution of the field length normalization factor
- which can lead to lower quality relevance calculations.
- ==================================================
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