HIVE-8309 : CBO: Fix OB by removing constraining DT, Use external names for col Aliases, Remove unnecessary Selects, Make DT Name counter query specific (John Pullokkaran via Ashutosh Chauhan)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/branch-0.14@1628750 13f79535-47bb-0310-9956-ffa450edef68