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https://issues.apache.org/jira/browse/CASSANDRA-4914?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13855583#comment-13855583
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Aleksey Yeschenko commented on CASSANDRA-4914:
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bq. In the case of Cassandra, however, one mayor concern would be that for
partitionable functions like sum, count, min or max, each node could do its
part of aggregation. For non-partitionable function like average or
percentiles, all the aggregation must be done at the coordinator.
This is not true at any RF > 1. The coordinator has to reconcile the partitions
before doing any kind of aggregation on them.
> Aggregate functions in CQL
> --------------------------
>
> Key: CASSANDRA-4914
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4914
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Vijay
> Assignee: Vijay
> Fix For: 2.1
>
>
> The requirement is to do aggregation of data in Cassandra (Wide row of column
> values of int, double, float etc).
> With some basic agree gate functions like AVG, SUM, Mean, Min, Max, etc (for
> the columns within a row).
> Example:
> SELECT * FROM emp WHERE empID IN (130) ORDER BY deptID DESC;
>
> empid | deptid | first_name | last_name | salary
> -------+--------+------------+-----------+--------
> 130 | 3 | joe | doe | 10.1
> 130 | 2 | joe | doe | 100
> 130 | 1 | joe | doe | 1e+03
>
> SELECT sum(salary), empid FROM emp WHERE empID IN (130);
>
> sum(salary) | empid
> -------------+--------
> 1110.1 | 130
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