As of 6.2.2 Columnstore doesn't support  JSON_* functions doing Select Handler execution.
We want to add support for the mentioned JSON_* functions into the existing functions and expressions runtime framework(FuncExp).
Here are the phases for the project:
- - get familiar with the code base, compilation and bootstrap process 
- - split the list of JSON_* functions into those suitable for distributed Select Handler execution and those aren't
- - get familiar with FuncExp details 
- - get familiar with MTR testing framework MCS  leverages
- - implement/borrow tests from MDB MTR test suite
- - implement suitable(see phase 2) JSON_* functions
There will be an additional simple task to add JSON data type as an alias for LONGTEXT(flex/bison parser tiny project).
Plz get in touch either here or in MariaDB Zulip chat
1. There are two query execution modes in MCS: fast distributed Select Handler execution and relatively slow but MDB-compatable Table execution.
2. Here is the automated bootstrap script.
3. FuncExp is a number of classes to describe an arbitrary tree of expressions doing projection, e.g. SELECT COS(c1 + c2) or doing filtering, e.g. SELECT c1 from t1 WHERE LENGTH(SUBSTRING(c1,2,2)) > 5. In most cases the implementation of a function looks as simple as this. An abstract part for FuncExp can be found in the MCS repo here.
4. Plz see this for the short info.