How to write a trigger in Cassandra to only detect updates of an existing row ?

[Kant Kodali <ka...@peernova.com>]

Hi all,
How to write a trigger in Cassandra to detect updates? My requirement is that I
want a trigger to alert me only when there is an update to an existing row and
looks like given the way INSERT and Update works this might be hard to do
because INSERT will just overwrite if there is an existing row and Update
becomes new insert where there is no row that belongs to certain partition key.
is there a way to solve this problem?
Thanks,

kant