presto-mysql/src/main/java/io/prestosql/plugin/mysql/MySqlClient.java/MySqlClient/jsonColumnMapping
class MySqlClient:    private ColumnMapping jsonColumnMapping()
    {
        return ColumnMapping.sliceMapping(
                jsonType,
                (resultSet, columnIndex) -> jsonParse(utf8Slice(resultSet.getString(columnIndex))),
                varcharWriteFunction(),
                DISABLE_PUSHDOWN);
    }