Elasticsearch Fundamentals: Indexing and Querying Data/

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Scripting and Runtime Fields

Scripting and Runtime Fields

Learn how to use the scripting and runtime fields in Elasticsearch.

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Scripting

In Elasticsearch, scripting refers to the ability to use scripts to perform operations on fields in documents stored in an index. This allows us to perform complex operations and calculations on data stored in Elasticsearch, such as updating and manipulating fields or scoring search results based on specific conditions.

Scripts can be written in different languages, such as Painless (default), JavaScript, and Groovy. In this lesson, we will focus on the Painless language.

Scripting syntax

Wherever scripting is supported in the Elasticsearch APIs, the scripts should have three important configurations:

  • lang: This specifies the language the script is written in. The default is Painless.

  • source: This contains the script to be executed or the ID for the stored script.

  • params: This specifies any named parameters passed into the script as variables. We use parameters instead of hard-coded values to decrease the compile time.

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

Painless scripting language

Painless 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.

Here is the essential syntax to remember when writing scripts in the Painless language:

  • Variables: They can be declared
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