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Tomas Salfischberger commented on CASSANDRA-2830:
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Good point, you could have a generic function implementation that is allowed to
do whatever it wants with an Iterator over the counter values and return a
single value. That would support easy implementation of SUM, MIN, MAX, AVG, but
also things like standard deviation and variance when the need arises.
> Allow summing of counter columns in CQL
> ---------------------------------------
>
> Key: CASSANDRA-2830
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2830
> Project: Cassandra
> Issue Type: New Feature
> Components: API
> Reporter: Tomas Salfischberger
> Priority: Minor
> Labels: CQL
>
> CQL could be extended with a method to calculate the sum of a set of counter
> columns. This avoids transferring a long list of counter columns to be summed
> by the client, while the server could calculate the total and instead only
> transfer that result. My proposal for the syntax (based on the COUNT()
> suggestion in the comments of CASSANDRA-1704):
> {code}SELECT SUM(<columnFrom>..<columnTo>) FROM <CF> WHERE ...{code}
> The simplest approach would be to only allow summing of counters under the
> same key, thus a query with a WHERE part that specifies multiple keys would
> return 1 result per key. This avoids summing values from different nodes.
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