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https://issues.apache.org/jira/browse/CASSANDRA-10707?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15169706#comment-15169706
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Benjamin Lerer commented on CASSANDRA-10707:
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[~slebresne] I tried the approach that you suggested but without success.
My idea was to increase the {{groupCount}} in the {{onPartitionClose()}} method
if the {{rowCount}} was not equals to the {{rowLimit}}. Unfortunatly, in the
case where the {{rowCount}} equals the {{rowLimit}} the next call return an
empty {{PartitionIterator}}. In this case the {{Counter}} does not receive any
notification and the pager consider that the data are exhausted. Without
callbacks it is difficult to adjust the {{groupCount}}. Performing the
modification outside of the {{CQLGroupByLimits}} is probably possible but will
force us to modify the {{DataLimits}} and {{QueryParser}} interfaces to expose
the {{rowCount}}.
I guess it is the reason why I ended up going in the direction of passing an
extra row up to the coordinator.
I do not deny that there might be a better way of doing the things but so far I
have not found it.
If you have some suggestions do not hesitate.
> Add support for Group By to Select statement
> --------------------------------------------
>
> Key: CASSANDRA-10707
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10707
> Project: Cassandra
> Issue Type: Improvement
> Components: CQL
> Reporter: Benjamin Lerer
> Assignee: Benjamin Lerer
>
> Now that Cassandra support aggregate functions, it makes sense to support
> {{GROUP BY}} on the {{SELECT}} statements.
> It should be possible to group either at the partition level or at the
> clustering column level.
> {code}
> SELECT partitionKey, max(value) FROM myTable GROUP BY partitionKey;
> SELECT partitionKey, clustering0, clustering1, max(value) FROM myTable GROUP
> BY partitionKey, clustering0, clustering1;
> {code}
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