Thank you for really quick reply! I tried both enabling deprecated option
innodb_large_prefix on latest MySQL 5.6.x and installing latest MySQL 5.7.x with this option enabled by default. Neither did help, I am still getting the error above.
Actually I don't think that tweaking DB server config can solve this issue since what your update tries to do is NOT supported by MySQL for fields of type
IMHO the reason why this error occurs is wrong field type for
slug field. In MySQL database it should be
VARCHAR(255) rather than
This comparison should give you a clear hint how to fix the issue: