What is expression in script field in Kibana and How to use it?

[kartikeya_sharma_13 (Kartikeya Sharma)]

I am wondering what is the usage of expression in the drop down of script field in lang option and how can i leverage that option .

[rashmi (kulkarni)]

Hi Kartikeya

The expressions what you see in the drop down is Lucene expressions. http://lucene.apache.org/core/4_9_0/expressions/index.html?org/apache/lucene/expressions/js/package-summary.html
Currently Kibana only supports Lucene expressions in script fields, for security reasons.

Here are some additional documentation links : https://www.elastic.co/guide/en/kibana/current/scripted-fields.html

Thanks
Rashmi

[kartikeya_sharma_13 (Kartikeya Sharma)]

Hi Rashmi,

Thanks for the response I was looking into both expression and painless , the only thing which i noticed in either of them is i cannot is comparison operators in painless , rest i guess is same .
Also Can i use the script fields for extracting other fields . I tried this but got failed.

Thanks