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From "Hiller, Dean" <>
Subject Re: random thoughts for MUCH faster key lookup in cassandra
Date Wed, 29 May 2013 16:58:40 GMT
I forgot the random partitioner can be switched out.  We don't use ordered partitioner so I
had forgotten about that one.  I guess it could only be a random partitioner type option :(.
 I think 80% of projects use random partitioner though, right?

In fact, we use PlayOrm queries so the indice are ordered and we can still get stuff back
in order even though we are on random partitioner in cassandra.


From: Andy Twigg <<>>
Reply-To: "<>" <<>>
Date: Wednesday, May 29, 2013 10:51 AM
To: "<>" <<>>
Subject: Re: random thoughts for MUCH faster key lookup in cassandra

How would you implement range queries?

On 29 May 2013 17:49, Hiller, Dean <<>>
We recently ran into too much data in one CF because LCS can't really run in parallel on one
CF in a single tier which got me thinking, why doesn't the CF directoy have 100 or 1000 directories
0-999 and cassandra hash the key to which directory it would go in and then put it in one
of the sstables in that directory.  This would lead to

 1.  Parallel compaction of LCS in a single CF !!!!  Yeah, faster compactions since there
is less to sort in each directory(and it can be done in parallel too)
 2.  Help with fast key lookups as it hashes to one of the 1000 directories very quickly and
then just needs to find the key in one of the sstables which are sorted (there would be 1000x
less sstables in each directory than in one big CF)

Am I on crack here? Or does that seem like it would be a pretty good direction to go?

Maybe this is only because our system has 98% of it's data in one CF while other systems have
10% of their data in each CF though.  I still tend to think a lot of people will end up with
80% of their data in one CF and 20% in all the other CF's…isn't pareto's principal a natural
tendency and if it is, maybe the above feature should be considered?


Dr Andy Twigg
Junior Research Fellow, St Johns College, Oxford
Room 351, Department of Computer Science<> | +447799647538

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