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From AndreaKinn <kinn6...@hotmail.it>
Subject Best way to deriving streams from another one
Date Sun, 10 Sep 2017 20:15:18 GMT
Hi,
I have a data stream resulting from an operation executed on a data stream
of data.
Essentially I want to obtain two different streams from that one to send
their to different cassandra tables.

I.e.:

datastream 0 composed by Tuple3<Val1, Val2, Val3>

I want to have:

 a datastream 1 composed by every triple <Val1,Val2,Val3> of datastream 0
where Val2 > X
and
a data stream 2 composed by every couple <Val1, Val3>.

This lied me to have two datastreams with Tuples of different arity (3 and
2).

Currently I have implemented it getting the 0 datastream and then calling
separately a map function to retrieve datastream 2 and a flatmap function to
retrieve datastream 1. So I have two different prepared statement of
Cassandra called on the two different streams. 
It works fine.

However this solutions looks really awful and inefficient, there is a more
elegant alternative?

I tried also to send towards Cassandra a datastream<Val1,Val2,Val3> and
select in the statement just two values (in this way I should use just the
flatmap operator) but during the execution raise an exception on it.



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