- Elasticsearch Guide: other versions:
- What is Elasticsearch?
- What’s new in 7.17
- Quick start
- Set up Elasticsearch
- Installing Elasticsearch
- Configuring Elasticsearch
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- ILM: Manage the index lifecycle
- Overview
- Concepts
- Automate rollover
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- Configure a lifecycle policy
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- Some settings are not returned via the nodes settings API
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- cat aliases
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- Cluster APIs
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- Alias exists
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- Exists
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- Definitions
- Migration guide
- Release notes
- Elasticsearch version 7.17.27
- Elasticsearch version 7.17.26
- Elasticsearch version 7.17.25
- Elasticsearch version 7.17.24
- Elasticsearch version 7.17.23
- Elasticsearch version 7.17.22
- Elasticsearch version 7.17.21
- Elasticsearch version 7.17.20
- Elasticsearch version 7.17.19
- Elasticsearch version 7.17.18
- Elasticsearch version 7.17.17
- Elasticsearch version 7.17.16
- Elasticsearch version 7.17.15
- Elasticsearch version 7.17.14
- Elasticsearch version 7.17.13
- Elasticsearch version 7.17.12
- Elasticsearch version 7.17.11
- Elasticsearch version 7.17.10
- Elasticsearch version 7.17.9
- Elasticsearch version 7.17.8
- Elasticsearch version 7.17.7
- Elasticsearch version 7.17.6
- Elasticsearch version 7.17.5
- Elasticsearch version 7.17.4
- Elasticsearch version 7.17.3
- Elasticsearch version 7.17.2
- Elasticsearch version 7.17.1
- Elasticsearch version 7.17.0
- Elasticsearch version 7.16.3
- Elasticsearch version 7.16.2
- Elasticsearch version 7.16.1
- Elasticsearch version 7.16.0
- Elasticsearch version 7.15.2
- Elasticsearch version 7.15.1
- Elasticsearch version 7.15.0
- Elasticsearch version 7.14.2
- Elasticsearch version 7.14.1
- Elasticsearch version 7.14.0
- Elasticsearch version 7.13.4
- Elasticsearch version 7.13.3
- Elasticsearch version 7.13.2
- Elasticsearch version 7.13.1
- Elasticsearch version 7.13.0
- Elasticsearch version 7.12.1
- Elasticsearch version 7.12.0
- Elasticsearch version 7.11.2
- Elasticsearch version 7.11.1
- Elasticsearch version 7.11.0
- Elasticsearch version 7.10.2
- Elasticsearch version 7.10.1
- Elasticsearch version 7.10.0
- Elasticsearch version 7.9.3
- Elasticsearch version 7.9.2
- Elasticsearch version 7.9.1
- Elasticsearch version 7.9.0
- Elasticsearch version 7.8.1
- Elasticsearch version 7.8.0
- Elasticsearch version 7.7.1
- Elasticsearch version 7.7.0
- Elasticsearch version 7.6.2
- Elasticsearch version 7.6.1
- Elasticsearch version 7.6.0
- Elasticsearch version 7.5.2
- Elasticsearch version 7.5.1
- Elasticsearch version 7.5.0
- Elasticsearch version 7.4.2
- Elasticsearch version 7.4.1
- Elasticsearch version 7.4.0
- Elasticsearch version 7.3.2
- Elasticsearch version 7.3.1
- Elasticsearch version 7.3.0
- Elasticsearch version 7.2.1
- Elasticsearch version 7.2.0
- Elasticsearch version 7.1.1
- Elasticsearch version 7.1.0
- Elasticsearch version 7.0.0
- Elasticsearch version 7.0.0-rc2
- Elasticsearch version 7.0.0-rc1
- Elasticsearch version 7.0.0-beta1
- Elasticsearch version 7.0.0-alpha2
- Elasticsearch version 7.0.0-alpha1
- Dependencies and versions
How to write scripts
editHow to write scripts
editWherever scripting is supported in the Elasticsearch APIs, the syntax follows the same pattern; you specify the language of your script, provide the script logic (or source), and add parameters that are passed into the script:
"script": { "lang": "...", "source" | "id": "...", "params": { ... } }
-
lang
-
Specifies the language the script is written in. Defaults to
painless
. -
source
,id
-
The script itself, which you specify as
source
for an inline script orid
for a stored script. Use the stored script APIs to create and manage stored scripts. -
params
- Specifies any named parameters that are passed into the script as variables. Use parameters instead of hard-coded values to decrease compile time.
Write your first script
editPainless is the default scripting language for Elasticsearch. It is secure, performant, and provides a natural syntax for anyone with a little coding experience.
A Painless script is structured as one or more statements and optionally has one or more user-defined functions at the beginning. A script must always have at least one statement.
The Painless execute API provides the ability to test a script with simple user-defined parameters and receive a result. Let’s start with a complete script and review its constituent parts.
First, index a document with a single field so that we have some data to work with:
PUT my-index-000001/_doc/1 { "my_field": 5 }
We can then construct a script that operates on that field and run evaluate the
script as part of a query. The following query uses the
script_fields
parameter of the search API to retrieve a
script valuation. There’s a lot happening here, but we’ll break it down the
components to understand them individually. For now, you only need to
understand that this script takes my_field
and operates on it.
GET my-index-000001/_search { "script_fields": { "my_doubled_field": { "script": { "source": "doc['my_field'].value * params['multiplier']", "params": { "multiplier": 2 } } } } }
The script
is a standard JSON object that defines scripts under most APIs
in Elasticsearch. This object requires source
to define the script itself. The
script doesn’t specify a language, so it defaults to Painless.
Use parameters in your script
editThe first time Elasticsearch sees a new script, it compiles the script and stores the
compiled version in a cache. Compilation can be a heavy process. Rather than
hard-coding values in your script, pass them as named params
instead.
For example, in the previous script, we could have just hard coded values and
written a script that is seemingly less complex. We could just retrieve the
first value for my_field
and then multiply it by 2
:
"source": "return doc['my_field'].value * 2"
Though it works, this solution is pretty inflexible. We have to modify the script source to change the multiplier, and Elasticsearch has to recompile the script every time that the multiplier changes.
Instead of hard-coding values, use named params
to make scripts flexible, and
also reduce compilation time when the script runs. You can now make changes to
the multiplier
parameter without Elasticsearch recompiling the script.
"source": "doc['my_field'].value * params['multiplier']", "params": { "multiplier": 2 }
You can compile up to 150 scripts per 5 minutes by default. For ingest contexts, the default script compilation rate is unlimited.
script.context.field.max_compilations_rate=100/10m
If you compile too many unique scripts within a short time, Elasticsearch
rejects the new dynamic scripts with a circuit_breaking_exception
error.
Shorten your script
editUsing syntactic abilities that are native to Painless, you can reduce verbosity in your scripts and make them shorter. Here’s a simple script that we can make shorter:
GET my-index-000001/_search { "script_fields": { "my_doubled_field": { "script": { "lang": "painless", "source": "return doc['my_field'].value * params.get('multiplier');", "params": { "multiplier": 2 } } } } }
Let’s look at a shortened version of the script to see what improvements it includes over the previous iteration:
GET my-index-000001/_search { "script_fields": { "my_doubled_field": { "script": { "source": "doc['my_field'].value * params['multiplier']", "params": { "multiplier": 2 } } } } }
This version of the script removes several components and simplifies the syntax significantly:
-
The
lang
declaration. Because Painless is the default language, you don’t need to specify the language if you’re writing a Painless script. -
The
return
keyword. Painless automatically uses the final statement in a script (when possible) to produce a return value in a script context that requires one. -
The
get
method, which is replaced with brackets[]
. Painless uses a shortcut specifically for theMap
type that allows us to use brackets instead of the lengthierget
method. -
The semicolon at the end of the
source
statement. Painless does not require semicolons for the final statement of a block. However, it does require them in other cases to remove ambiguity.
Use this abbreviated syntax anywhere that Elasticsearch supports scripts, such as when you’re creating runtime fields.
Store and retrieve scripts
editYou can store and retrieve scripts from the cluster state using the stored script APIs. Stored scripts reduce compilation time and make searches faster.
Unlike regular scripts, stored scripts require that you specify a script
language using the lang
parameter.
To create a script, use the create stored script
API. For example, the following request creates a stored script named
calculate-score
.
POST _scripts/calculate-score { "script": { "lang": "painless", "source": "Math.log(_score * 2) + params['my_modifier']" } }
You can retrieve that script by using the get stored script API.
GET _scripts/calculate-score
To use the stored script in a query, include the script id
in the script
declaration:
GET my-index-000001/_search { "query": { "script_score": { "query": { "match": { "message": "some message" } }, "script": { "id": "calculate-score", "params": { "my_modifier": 2 } } } } }
To delete a stored script, submit a delete stored script API request.
DELETE _scripts/calculate-score
Update documents with scripts
editYou can use the update API to update documents with a specified script. The script can update, delete, or skip modifying the document. The update API also supports passing a partial document, which is merged into the existing document.
First, let’s index a simple document:
PUT my-index-000001/_doc/1 { "counter" : 1, "tags" : ["red"] }
To increment the counter, you can submit an update request with the following script:
POST my-index-000001/_update/1 { "script" : { "source": "ctx._source.counter += params.count", "lang": "painless", "params" : { "count" : 4 } } }
Similarly, you can use an update script to add a tag to the list of tags. Because this is just a list, the tag is added even it exists:
POST my-index-000001/_update/1 { "script": { "source": "ctx._source.tags.add(params['tag'])", "lang": "painless", "params": { "tag": "blue" } } }
You can also remove a tag from the list of tags. The remove
method of a Java
List
is available in Painless. It takes the index of the element you
want to remove. To avoid a possible runtime error, you first need to make sure
the tag exists. If the list contains duplicates of the tag, this script just
removes one occurrence.
POST my-index-000001/_update/1 { "script": { "source": "if (ctx._source.tags.contains(params['tag'])) { ctx._source.tags.remove(ctx._source.tags.indexOf(params['tag'])) }", "lang": "painless", "params": { "tag": "blue" } } }
You can also add and remove fields from a document. For example, this script
adds the field new_field
:
POST my-index-000001/_update/1 { "script" : "ctx._source.new_field = 'value_of_new_field'" }
Conversely, this script removes the field new_field
:
POST my-index-000001/_update/1 { "script" : "ctx._source.remove('new_field')" }
Instead of updating the document, you can also change the operation that is
executed from within the script. For example, this request deletes the document
if the tags
field contains green
. Otherwise it does nothing (noop
):
POST my-index-000001/_update/1 { "script": { "source": "if (ctx._source.tags.contains(params['tag'])) { ctx.op = 'delete' } else { ctx.op = 'none' }", "lang": "painless", "params": { "tag": "green" } } }
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