Analysis: The JSON functions(JSON_ARRAY[OBJECT|ARRAY_APPEND|ARRAY_INSERT|INSERT|SET|REPLACE]) result is truncated when the function is called based on LONGTEXT field. The overflow occurs when computing the result length due to the LONGTEXT max length is same as uint32 max length. It lead to wrong result length.
Fix: Add static_cast<ulonglong> to avoid uint32 overflow and fix the arguments used.