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Deprecate document _boost

Fixes #4664
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clintongormley committed Jan 9, 2014
1 parent 13c88da commit 3ab73ab9573bf1c07ac85320d3a4e0a2b8f577e5
Showing with 40 additions and 0 deletions.
  1. +40 −0 docs/reference/mapping/fields/boost-field.asciidoc
@@ -1,6 +1,8 @@
[[mapping-boost-field]]
=== `_boost`
deprecated[1.0.0.RC1,See <<function-score-instead-of-boost>>]
Boosting is the process of enhancing the relevancy of a document or
field. Field level mapping allows to define explicit boost level on a
specific field. The boost field mapping (applied on the
@@ -30,3 +32,41 @@ following JSON document will be indexed with a boost value of `2.2`:
"message" : "This is a tweet!"
}
--------------------------------------------------
[[function-score-instead-of-boost]]
==== Function score instead of boost
Support for document boosting via the `_boost` field has been removed
from Lucene and is deprecated in Elasticsearch as of v1.0.0.RC1. The
implementation in Lucene resulted in unpredictable result when
used with multiple fields or multi-value fields.
Instead, the <<query-dsl-function-score-query>> can be used to achieve
the desired functionality by boosting each document by the value in
any field the document:
[source,js]
--------------------------------------------------
{
"query": {
"function_score": {
"query": { <1>
"match": {
"title": "your main query"
}
},
"functions": [{
"script_score": { <2>
"script": "doc['my_boost_field'].value"
}
}],
"score_mode": "multiply"
}
}
}
--------------------------------------------------
<1> The original query, now wrapped in a `function_score` query.
<2> This script returns the value in `my_boost_field`, which is then
multiplied by the query `_score` for each document.

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