If you use JSON UDFs in MySQL 5.6 there are a few things to consider before upgrading to MySQL 5.7. From a schema perspective, if you have JSON stored in text columns you can decide when to convert those columns to the new JSON datatype after you upgrade, but due to namespace collisions and format differences it's probably not safe to upgrade without dropping some or all of the existing UDFs and updating your queries that use those UDFs.
Read on for details...
Namespace collisions
There are 15 functions in JSON UDFs version 0.4.0. Nine of those names are used by native JSON functions in MySQL 5.7, so it's not possible to continue using those nine UDFs in MySQL 5.7. Therefore before you upgrade you should probably drop these UDFs:
DROP FUNCTION IF EXISTS json_append; DROP FUNCTION IF
EXISTS json_depth; DROP FUNCTION IF EXISTS json_extract; DROP
FUNCTION IF EXISTS json_merge; DROP FUNCTION IF EXISTS …