There are times when we use scripts, update data, scripted fields, and many more use cases. Prior to version 5.x, groovy was the default language for your scripts. We even did not specify which scripts we wanted to use back then. Since these scripts were executed remotely security was always a concern that Elastic Team had to address. This became the reason for designing Painless.
Painless is both secure and efficient when it comes to performance. It has a similar syntax as of Groovy so it is also easy to learn and use. For most of the cases, you don't need to make changes to your previously written scripts. All you need to add is a parameter called lang and specify the value as painless.
To define a variable in painless, simply use the following:
def myVar = 'my-value';
We don't need to specify any type. At runtime, the type of variable will be detected whatever suits appropriate. Painless supports all variable types defined by Java.
To define an array, use...