With testing TEIID-3847 Hive 1.2.1 failed to compare appropriately with a timestamp string literal in the source sql containing .0 fractional seconds:

t = '2000-01-01 12:00:00.0' – did not work
But the following does
t = '2000-01-01 12:00:00'
t = cast('2000-01-01 12:00:00.0' as timestamp)