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This commit updates the `dense_vector` docs to include information on the new `index`, `similarity`, and `index_options` parameters. It also tries to clarify the difference between `similarity` and `index_options` with the existing parameters that have the same name. Relates to #78473.
50 lines
1.5 KiB
Text
50 lines
1.5 KiB
Text
[[similarity]]
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=== `similarity`
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{es} allows you to configure a text scoring algorithm or _similarity_
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per field. The `similarity` setting provides a simple way of choosing a
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text similarity algorithm other than the default `BM25`, such as `boolean`.
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Only text-based field types like <<text,`text`>> and <<keyword,`keyword`>>
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support this configuration.
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Custom similarities can be configured by tuning the parameters of the built-in
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similarities. For more details about this expert options, see the
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<<index-modules-similarity,similarity module>>.
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The only similarities which can be used out of the box, without any further
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configuration are:
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`BM25`::
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The {wikipedia}/Okapi_BM25[Okapi BM25 algorithm]. The
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algorithm used by default in {es} and Lucene.
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`boolean`::
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A simple boolean similarity, which is used when full-text ranking is not needed
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and the score should only be based on whether the query terms match or not.
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Boolean similarity gives terms a score equal to their query boost.
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The `similarity` can be set on the field level when a field is first created,
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as follows:
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[source,console]
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--------------------------------------------------
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PUT my-index-000001
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{
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"mappings": {
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"properties": {
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"default_field": { <1>
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"type": "text"
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},
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"boolean_sim_field": {
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"type": "text",
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"similarity": "boolean" <2>
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}
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}
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}
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}
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--------------------------------------------------
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<1> The `default_field` uses the `BM25` similarity.
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<2> The `boolean_sim_field` uses the `boolean` similarity.
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