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How to use scripts
editHow to use scripts
editWherever scripting is supported in the Elasticsearch API, the syntax follows the same pattern:
The language the script is written in, which defaults to |
|
The script itself which may be specified as |
|
Any named parameters that should be passed into the script. |
For example, the following script is used in a search request to return a scripted field:
PUT my_index/my_type/1 { "my_field": 5 } GET my_index/_search { "script_fields": { "my_doubled_field": { "script": { "lang": "expression", "source": "doc['my_field'] * multiplier", "params": { "multiplier": 2 } } } } }
Script Parameters
edit-
lang
-
Specifies the language the script is written in. Defaults to
painless
but may be set to any of languages listed in Scripting. The default language may be changed in theelasticsearch.yml
config file by settingscript.default_lang
to the appropriate language. -
source
,id
-
Specifies the source of the script. An
inline
script is specifiedsource
as in the example above. Astored
script is specifiedid
and is retrieved from the cluster state (see Stored Scripts). -
params
- Specifies any named parameters that are passed into the script as variables.
Prefer parameters
The first time Elasticsearch sees a new script, it compiles it and stores the compiled version in a cache. Compilation can be a heavy process.
If you need to pass variables into the script, you should pass them in as
named params
instead of hard-coding values into the script itself. For
example, if you want to be able to multiply a field value by different
multipliers, don’t hard-code the multiplier into the script:
"source": "doc['my_field'] * 2"
Instead, pass it in as a named parameter:
"source": "doc['my_field'] * multiplier", "params": { "multiplier": 2 }
The first version has to be recompiled every time the multiplier changes. The second version is only compiled once.
If you compile too many unique scripts within a small amount of time,
Elasticsearch will reject the new dynamic scripts with a
circuit_breaking_exception
error. By default, up to 15 inline scripts per
minute will be compiled. You can change this setting dynamically by setting
script.max_compilations_rate
.
Stored Scripts
editScripts may be stored in and retrieved from the cluster state using the
_scripts
end-point.
Request Examples
editThe following are examples of using a stored script that lives at
/_scripts/{id}
.
First, create the script called calculate-score
in the cluster state:
POST _scripts/calculate-score { "script": { "lang": "painless", "source": "Math.log(_score * 2) + params.my_modifier" } }
This same script can be retrieved with:
GET _scripts/calculate-score
Stored scripts can be used by specifying the id
parameters as follows:
GET _search { "query": { "script": { "script": { "id": "calculate-score", "params": { "my_modifier": 2 } } } } }
And deleted with:
DELETE _scripts/calculate-score
Script Caching
editAll scripts are cached by default so that they only need to be recompiled
when updates occur. By default, scripts do not have a time-based expiration, but
you can change this behavior by using the script.cache.expire
setting.
You can configure the size of this cache by using the script.cache.max_size
setting.
By default, the cache size is 100
.
The size of stored scripts is limited to 65,535 bytes. This can be
changed by setting script.max_size_in_bytes
setting to increase that soft
limit, but if scripts are really large then a
native script engine should be considered.