How to use scripts in elastic search

Published On: 18 July 2018.By vipin garg.

Digital Engineering
Ecommerce
General

How to use scripts in elastic search

Wherever scripting is supported in the Elasticsearch API, the syntax follows the same pattern:

 "script": {
    "lang":   "...",  
    "source" | "id": "...", 
    "params": { ... } 
  }

1

2

3

4

5

"script": {

"lang": "...",

"source" | "id": "...",

"params": { ... }

}

The language the script is written in, which defaults to painless. The script itself which may be specified as source for an inline script or id for a stored script. 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/_doc/1
{
  "my_field": 5
}

GET my_index/_search
{
  "script_fields": {
    "my_doubled_field": {
      "script": {
        "lang":   "expression",
        "source": "doc['my_field'] * multiplier",
        "params": {
          "multiplier": 2
        }
      }
    }
  }
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

PUT my_index/_doc/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

lang

Specifies the language the script is written in. Defaults to painless.

source, id

Specifies the source of the script. An inline script is specified source as in the example above. A stored script is specified id and is retrieved from the cluster state (see Stored Scripts).

params

Specifies any named parameters that are passed into the script as variables.

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 paramsinstead 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"

1	"source": "doc['my_field'] * 2"

Instead, pass it in as a named parameter:

"source": "doc['my_field'] * multiplier",
  "params": {
    "multiplier": 2
  }

1

2

3

4

"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 Scriptsedit

Scripts may be stored in and retrieved from the cluster state using the _scripts end-point.

Request Examplesedit

The 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"
  }
}

1

2

3

4

5

6

7

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

1	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
        }
      }
    }
  }
}

1

2

3

4

5

6

7

8

9

10

11

12

13

GET _search

{

"query": {

"script": {

"id": "calculate-score",

"params": {

"my_modifier": 2

}

And deleted with:

DELETE _scripts/calculate-score

1	DELETE _scripts/calculate-score

How to use scripts in elastic search