Now if the two sides of comparison is of different type, we always convert both to double and compare. It was a slight regression from the change in https://issues.apache.org/jira/browse/HIVE-1638. The old UDFOP<Comparison>, using GenericUDFBridge, always tried to find common type first.
The worse case is this: If you did "WHERE <BIGINT_COLUMN> = 0 ", we always convert the column and 0 to double and compare, which is wasteful, though it is usually a minor costs in the system. But it is easy to fix.