The prepare/close step of scalar function is already supported in execution framework, We only need to do is that support it in syntax and meta in frontend.
In addition, 'Hive' binary type of scalar function NOT supports prepare/close step, we need to make it supports.
Random distribution is no longer supported since version 0.9.
And we need a way to convert the random distribution to hash distribution.
ALTER TABLE db.tbl SET ("distribution_type" = "hash");
