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https://issues.apache.org/jira/browse/CASSANDRA-4914?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14112098#comment-14112098
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Sylvain Lebresne commented on CASSANDRA-4914:
---------------------------------------------
I have not yet reviewed this, but at very quick glance, I see nothing that
handles the paging of aggregations: we don't want to load everything in memory
with a single query. I'll note that we already support one hard-coded
aggregation function, COUNT, and you can look at how it's handled by
SelectStatement to see what I mean by "paging internally". Ideally the patch
for this should replace this currently hardcoded COUNT to use the general
mechanism for aggregation. Also, we also want to support syntax like {{SELECT
AVG(*) FROM ...}} which I don't think this patch handles (since it doesn't
modify the parser and it would need to).
> Aggregation functions in CQL
> ----------------------------
>
> Key: CASSANDRA-4914
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4914
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Vijay
> Assignee: Benjamin Lerer
> Labels: cql, docs
> Fix For: 3.0
>
> Attachments: CASSANDRA-4914.txt
>
>
> 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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