[[modules-scripting]]
== Scripting

The scripting module enables you to use scripts to evaluate custom
expressions. For example, you could use a script to return "script fields"
as part of a search request or evaluate a custom score for a query.

TIP: Elasticsearch now has a built-in scripting language called _Painless_
that provides a more secure alternative for implementing
scripts for Elasticsearch. We encourage you to try it out --
for more information, see <<modules-scripting-painless, Painless Scripting Language>>.

The default scripting language is http://groovy-lang.org/[groovy].
Additional `lang` plugins enable you to run scripts written in other languages.
Everywhere a script can be used, you can include a `lang` parameter
to specify the language of the script.

[float]
=== General-purpose languages:

These languages can be used for any purpose in the scripting APIs,
and give the most flexibility.

[cols="<,<,<",options="header",]
|=======================================================================
|Language
    |Sandboxed
    |Required plugin

|<<modules-scripting-painless, `painless`>>
    |yes
    |built-in

|<<modules-scripting-groovy, `groovy`>>
    |<<modules-scripting-security, no>>
    |built-in

|{plugins}/lang-javascript.html[`javascript`]
    |<<modules-scripting-security, no>>
    |{plugins}/lang-javascript.html[`lang-javascript`]

|{plugins}/lang-python.html[`python`]
    |<<modules-scripting-security, no>>
    |{plugins}/lang-python.html[`lang-python`]

|=======================================================================

[float]
=== Special-purpose languages:

These languages are less flexible, but typically have higher performance for
certain tasks.

[cols="<,<,<,<",options="header",]
|=======================================================================
|Language
    |Sandboxed
    |Required plugin
    |Purpose

|<<modules-scripting-expression, `expression`>>
    |yes
    |built-in
    |fast custom ranking and sorting

|<<search-template, `mustache`>>
    |yes
    |built-in
    |templates

|<<modules-scripting-native, `java`>>
    |n/a
    |you write it!
    |expert API

|=======================================================================

[WARNING]
.Scripts and security
=================================================

Languages that are sandboxed are designed with security in mind. However, non-
sandboxed languages can be a security issue, please read
<<modules-scripting-security, Scripting and security>> for more details.

=================================================


include::scripting/using.asciidoc[]

include::scripting/fields.asciidoc[]

include::scripting/security.asciidoc[]

include::scripting/groovy.asciidoc[]

include::scripting/painless.asciidoc[]

include::scripting/painless-syntax.asciidoc[]

include::scripting/expression.asciidoc[]

include::scripting/native.asciidoc[]

include::scripting/advanced-scripting.asciidoc[]