PTF partitions apply the defensive mode of assuming that partitions will not fit in memory. Because of this there is a significant deserialization overhead when accessing elements.
Allow the user to specify that there is enough memory to hold partitions through a 'hive.ptf.partition.fits.in.mem' option.
Savings depends on partition size and in case of windowing the number of UDAFs and the window ranges. For eg for the following (admittedly extreme) case the PTFOperator exec times went from 39 secs to 8 secs.