eg:
select str_to_date('2014-12-21 12%3A34%3A56', '%Y-%m-%d %H%%3A%i%%3A%s');
select unix_timestamp('2007-11-30 10:30%3A19', '%Y-%m-%d %H:%i%%3A%s');
This also enable us to extract column fields from HDFS file path with contains '%'.
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");
