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From Peter Schuller <>
Subject Re: Counters in 0.8 -- conditional?
Date Wed, 02 Feb 2011 22:46:34 GMT
> Thanks. Just wanted to note that counting the number of rows where foo=bar is
> a fairly ubiquitous task in db applications. In case of "big data",
> trafficking all these data to client just to count something isn't optimal
> at all.

You can ask Cassandra to do the counting, but the cost is still going
to involve reading the data on the Cassandra end. Hence, O(n) rather
than O(1). (It would obviously be nice if counts could be done O(1),
but it's not trivial to implement or obvious how to do it in order for
it to be generally useful. Even non-distributed databases like
PostgreSQL have issues with that.)

/ Peter Schuller

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