One of the great things in Elasticsearch is its scripting capabilities. You can use script for calculating score, text-based scoring, data filtering, and data analysis. Although scripting can be slow in some cases, such as calculating the score for each document, we think that this part of Elasticsearch is important. Because of this, we decided that this section should bring you the information about the changes and will extend the information present in the Elasticsearch Server Second Edition book.
Elasticsearch scripting has gone through a lot of refactoring in version 1.0 and in the versions that came after that. Because of those changes, some users were lost as to why their scripts stopped working when upgrading to version 1.2 of Elasticsearch and what is happening in general. This section will try to give you an insight on what to expect.