Make JSONType a MEDIUMBLOB instead of a BLOB under mysql.
These can have 16 MB of data instead of 65 KB - tool shed repositories have encountered problems with the 65 KB limit - though other columns might as well.
Database migration to grow mysql blobs.
Should address the following issues

https://trello.com/c/RbW6pOd2
https://trello.com/c/lvz4OQR1
https://trello.com/c/Hv5iIweU
Merged in jmchilton/galaxy-central-fork-1 (pull request #558)

Make JSONType columns bigger in MySQL