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");
1. Support specifying label to Insert Into stmt.
INSERT INTO tbl1 WITH LABEL label1 ...;
2. Return job' state corresponding to the existing label in result of stream load.
...
"Status": "Label Already Exists",
"ExistingJobStatus": "FINISHED"
...
3. Return the recent 2000 transactions in SHOW PROC '/transactions'
