A common use case when working with Elasticsearch(ES) are the creation of dynamic fields, performing calculations on fields on the fly, modifying the scoring based upon a logic, etc. In order to perform these operations, Elasticsearch supports scripting.

Since the earlier versions of ES, it supported scripting, but the scripting language has evolved over the ES releases. Starting with MVEL prior version 1.4, Groovy (post version 1.4), and now the latest entry “Painless” starting ES 5.0, the scripting in ES has evolved. A key reason for this evolution is the need for faster, safer and simpler scripting language.

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Painless uses a Java-style syntax that is similar to Groovy. In fact, most Painless scripts are also valid Groovy, and simple Groovy scripts are typically valid Painless. (This specification assumes you have at least a passing familiarity with Java and related languages.)

Painless is essentially a subset of Java with some additional scripting language features that make scripts easier to write. However, there are some important differences, particularly with the casting model. For more detailed conceptual information about the basic constructs that Java and Painless share, refer to the corresponding topics in the Java Language Specification.

Painless scripts are parsed and compiled using the ANTLR4 and ASM libraries. Painless scripts are compiled directly into Java byte code and executed against a standard Java Virtual Machine. This specification uses ANTLR4 grammar notation to describe the allowed syntax. However, the actual Painless grammar is more compact than that shown here. Painless is a simple and secure scripting language designed specifically for use with Elasticsearch. It is the default scripting language for Elasticsearch and can safely be used for inline and stored scripts.

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As some of our readers know, we’ve been working through a tutorial series on Elasticsearch scripting. We’ve seen the power and critical importance of scripting, a number of basic examples, and various types of sorting that you can perform in ES. Here in this article, we concentrate on applying filters through query scripts because you’ll get results more quickly when you use filters instead of queries.

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In our previous article on the scripting features of Elasticsearch, our readers saw how easy it is to perform basic operations through scripting—adding new fields to an index, managing arrays, and removing fields.

This is the second article in our series and is about various types of sorting that you can perform through Elasticsearch scripting. These operations are a bit more complex, and we provide a number of in-depth examples.

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Perhaps the most useful and powerful feature of Elasticsearch is its scripting capabilities.

Elasticsearch users can perform a variety of operations by enabling and exercising the script modules. Scripts can be used for a broad range of tasks, such as returning specific fields in a search request or modifying specific elements in a field. Read this article to learn about the benefits of this essential feature, and step through some basic tutorials on implementing scripts in Elasticsearch.

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In this article, we continue our series on Getting to Know Elasticsearch. In this series, Technical writer John Vanderzyden, a technologist for over two decades but with no previous experience in Elasticsearch, is writing a series of guest posts documenting how easy it is to ramp up as a newbie to Qbox. He’s especially keen to help individuals who are new to these technologies. The first post in the series, Welcome to the ELK Stack, introduced the series. — Mark Brandon

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