elasticsearch/docs/reference/scripting/engine.asciidoc
Liam Thompson 33a71e3289
[DOCS] Refactor book-scoped variables in docs/reference/index.asciidoc (#107413)
* Remove `es-test-dir` book-scoped variable

* Remove `plugins-examples-dir` book-scoped variable

* Remove `:dependencies-dir:` and `:xes-repo-dir:` book-scoped variables

- In `index.asciidoc`, two variables (`:dependencies-dir:` and `:xes-repo-dir:`) were removed.
- In `sql/index.asciidoc`, the `:sql-tests:` path was updated to fuller path
- In `esql/index.asciidoc`, the `:esql-tests:` path was updated idem

* Replace `es-repo-dir` with `es-ref-dir`

* Move `:include-xpack: true` to few files that use it, remove from index.asciidoc
2024-04-17 14:37:07 +02:00

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[[modules-scripting-engine]]
== Advanced scripts using script engines
A `ScriptEngine` is a backend for implementing a scripting language. It may also
be used to write scripts that need to use advanced internals of scripting. For example,
a script that wants to use term frequencies while scoring.
The plugin {plugins}/plugin-authors.html[documentation] has more information on
how to write a plugin so that Elasticsearch will properly load it. To register
the `ScriptEngine`, your plugin should implement the `ScriptPlugin` interface
and override the `getScriptEngine(Settings settings)` method.
The following is an example of a custom `ScriptEngine` which uses the language
name `expert_scripts`. It implements a single script called `pure_df` which
may be used as a search script to override each document's score as
the document frequency of a provided term.
["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{elasticsearch-root}/plugins/examples/script-expert-scoring/src/main/java/org/elasticsearch/example/expertscript/ExpertScriptPlugin.java[expert_engine]
--------------------------------------------------
You can execute the script by specifying its `lang` as `expert_scripts`, and the name
of the script as the script source:
[source,console]
--------------------------------------------------
POST /_search
{
"query": {
"function_score": {
"query": {
"match": {
"body": "foo"
}
},
"functions": [
{
"script_score": {
"script": {
"source": "pure_df",
"lang" : "expert_scripts",
"params": {
"field": "body",
"term": "foo"
}
}
}
}
]
}
}
}
--------------------------------------------------
// TEST[skip:we don't have an expert script plugin installed to test this]