HIVE-8655: CBO: ppr_pushdown, udf_substr produces incorrect results due to broken tablesample handling (Sergey Shelukhin via Gunther Hagleitner)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1635575 13f79535-47bb-0310-9956-ffa450edef68