292 lines
9.2 KiB
Plaintext
292 lines
9.2 KiB
Plaintext
[[query-dsl-script-score-query]]
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=== Script score query
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++++
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<titleabbrev>Script score</titleabbrev>
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++++
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The `script_score` allows you to modify the score of documents that are
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retrieved by a query. This can be useful if, for example, a score
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function is computationally expensive and it is sufficient to compute
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the score on a filtered set of documents.
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To use `script_score`, you have to define a query and a script -
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a function to be used to compute a new score for each document returned
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by the query. For more information on scripting see
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<<modules-scripting, scripting documentation>>.
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Here is an example of using `script_score` to assign each matched document
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a score equal to the number of likes divided by 10:
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[source,js]
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--------------------------------------------------
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GET /_search
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{
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"query" : {
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"script_score" : {
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"query" : {
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"match": { "message": "elasticsearch" }
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},
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"script" : {
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"source" : "doc['likes'].value / 10 "
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}
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}
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}
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}
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--------------------------------------------------
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// CONSOLE
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==== Accessing the score of a document within a script
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Within a script, you can
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{ref}/modules-scripting-fields.html#scripting-score[access]
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the `_score` variable which represents the current relevance score of a
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document.
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==== Predefined functions within a Painless script
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You can use any of the available
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<<painless-api-reference, painless functions>> in the painless script.
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Besides these functions, there are a number of predefined functions
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that can help you with scoring. We suggest you to use them instead of
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rewriting equivalent functions of your own, as these functions try
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to be the most efficient by using the internal mechanisms.
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===== saturation
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`saturation(value,k) = value/(k + value)`
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[source,js]
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--------------------------------------------------
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"script" : {
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"source" : "saturation(doc['likes'].value, 1)"
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}
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--------------------------------------------------
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// NOTCONSOLE
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===== sigmoid
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`sigmoid(value, k, a) = value^a/ (k^a + value^a)`
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[source,js]
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--------------------------------------------------
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"script" : {
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"source" : "sigmoid(doc['likes'].value, 2, 1)"
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}
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--------------------------------------------------
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// NOTCONSOLE
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[[random-score-function]]
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===== Random score function
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`random_score` function generates scores that are uniformly distributed
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from 0 up to but not including 1.
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`randomScore` function has the following syntax:
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`randomScore(<seed>, <fieldName>)`.
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It has a required parameter - `seed` as an integer value,
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and an optional parameter - `fieldName` as a string value.
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[source,js]
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--------------------------------------------------
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"script" : {
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"source" : "randomScore(100, '_seq_no')"
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}
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--------------------------------------------------
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// NOTCONSOLE
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If the `fieldName` parameter is omitted, the internal Lucene
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document ids will be used as a source of randomness. This is very efficient,
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but unfortunately not reproducible since documents might be renumbered
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by merges.
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[source,js]
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--------------------------------------------------
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"script" : {
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"source" : "randomScore(100)"
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}
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--------------------------------------------------
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// NOTCONSOLE
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Note that documents that are within the same shard and have the
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same value for field will get the same score, so it is usually desirable
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to use a field that has unique values for all documents across a shard.
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A good default choice might be to use the `_seq_no`
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field, whose only drawback is that scores will change if the document is
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updated since update operations also update the value of the `_seq_no` field.
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[[decay-functions-numeric-fields]]
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===== Decay functions for numeric fields
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You can read more about decay functions
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{ref}/query-dsl-function-score-query.html#function-decay[here].
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* `double decayNumericLinear(double origin, double scale, double offset, double decay, double docValue)`
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* `double decayNumericExp(double origin, double scale, double offset, double decay, double docValue)`
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* `double decayNumericGauss(double origin, double scale, double offset, double decay, double docValue)`
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[source,js]
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--------------------------------------------------
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"script" : {
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"source" : "decayNumericLinear(params.origin, params.scale, params.offset, params.decay, doc['dval'].value)",
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"params": { <1>
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"origin": 20,
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"scale": 10,
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"decay" : 0.5,
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"offset" : 0
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}
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}
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--------------------------------------------------
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// NOTCONSOLE
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<1> Using `params` allows to compile the script only once, even if params change.
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===== Decay functions for geo fields
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* `double decayGeoLinear(String originStr, String scaleStr, String offsetStr, double decay, GeoPoint docValue)`
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* `double decayGeoExp(String originStr, String scaleStr, String offsetStr, double decay, GeoPoint docValue)`
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* `double decayGeoGauss(String originStr, String scaleStr, String offsetStr, double decay, GeoPoint docValue)`
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[source,js]
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--------------------------------------------------
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"script" : {
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"source" : "decayGeoExp(params.origin, params.scale, params.offset, params.decay, doc['location'].value)",
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"params": {
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"origin": "40, -70.12",
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"scale": "200km",
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"offset": "0km",
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"decay" : 0.2
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}
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}
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--------------------------------------------------
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// NOTCONSOLE
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===== Decay functions for date fields
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* `double decayDateLinear(String originStr, String scaleStr, String offsetStr, double decay, JodaCompatibleZonedDateTime docValueDate)`
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* `double decayDateExp(String originStr, String scaleStr, String offsetStr, double decay, JodaCompatibleZonedDateTime docValueDate)`
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* `double decayDateGauss(String originStr, String scaleStr, String offsetStr, double decay, JodaCompatibleZonedDateTime docValueDate)`
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[source,js]
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--------------------------------------------------
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"script" : {
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"source" : "decayDateGauss(params.origin, params.scale, params.offset, params.decay, doc['date'].value)",
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"params": {
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"origin": "2008-01-01T01:00:00Z",
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"scale": "1h",
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"offset" : "0",
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"decay" : 0.5
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}
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}
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--------------------------------------------------
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// NOTCONSOLE
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NOTE: Decay functions on dates are limited to dates in the default format
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and default time zone. Also calculations with `now` are not supported.
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===== Functions for vector fields
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<<vector-functions, Functions for vector fields>> are accessible through
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`script_score` query.
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==== Faster alternatives
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Script Score Query calculates the score for every hit (matching document).
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There are faster alternative query types that can efficiently skip
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non-competitive hits:
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* If you want to boost documents on some static fields, use
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<<query-dsl-rank-feature-query, Rank Feature Query>>.
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==== Transition from Function Score Query
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We are deprecating <<query-dsl-function-score-query, Function Score>>, and
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Script Score Query will be a substitute for it.
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Here we describe how Function Score Query's functions can be
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equivalently implemented in Script Score Query:
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[[script-score]]
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===== `script_score`
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What you used in `script_score` of the Function Score query, you
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can copy into the Script Score query. No changes here.
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[[weight]]
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===== `weight`
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`weight` function can be implemented in the Script Score query through
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the following script:
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[source,js]
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--------------------------------------------------
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"script" : {
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"source" : "params.weight * _score",
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"params": {
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"weight": 2
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}
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}
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--------------------------------------------------
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// NOTCONSOLE
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[[random-score]]
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===== `random_score`
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Use `randomScore` function
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as described in <<random-score-function, random score function>>.
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[[field-value-factor]]
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===== `field_value_factor`
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`field_value_factor` function can be easily implemented through script:
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[source,js]
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--------------------------------------------------
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"script" : {
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"source" : "Math.log10(doc['field'].value * params.factor)",
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params" : {
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"factor" : 5
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}
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}
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--------------------------------------------------
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// NOTCONSOLE
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For checking if a document has a missing value, you can use
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`doc['field'].size() == 0`. For example, this script will use
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a value `1` if a document doesn't have a field `field`:
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[source,js]
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--------------------------------------------------
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"script" : {
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"source" : "Math.log10((doc['field'].size() == 0 ? 1 : doc['field'].value()) * params.factor)",
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params" : {
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"factor" : 5
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}
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}
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--------------------------------------------------
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// NOTCONSOLE
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This table lists how `field_value_factor` modifiers can be implemented
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through a script:
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[cols="<,<",options="header",]
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|=======================================================================
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| Modifier | Implementation in Script Score
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| `none` | -
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| `log` | `Math.log10(doc['f'].value)`
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| `log1p` | `Math.log10(doc['f'].value + 1)`
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| `log2p` | `Math.log10(doc['f'].value + 2)`
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| `ln` | `Math.log(doc['f'].value)`
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| `ln1p` | `Math.log(doc['f'].value + 1)`
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| `ln2p` | `Math.log(doc['f'].value + 2)`
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| `square` | `Math.pow(doc['f'].value, 2)`
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| `sqrt` | `Math.sqrt(doc['f'].value)`
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| `reciprocal` | `1.0 / doc['f'].value`
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|=======================================================================
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[[decay-functions]]
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===== `decay functions`
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Script Score query has equivalent <<decay-functions, decay functions>>
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that can be used in script.
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include::{es-repo-dir}/vectors/vector-functions.asciidoc[]
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