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https://issues.apache.org/jira/browse/PHOENIX-2794?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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James Taylor updated PHOENIX-2794:
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Attachment: PHOENIX-2794_v2.patch
Please review, [~tdsilva]
> Flatten nested aggregate queries when possible
> ----------------------------------------------
>
> Key: PHOENIX-2794
> URL: https://issues.apache.org/jira/browse/PHOENIX-2794
> Project: Phoenix
> Issue Type: Bug
> Reporter: James Taylor
> Attachments: PHOENIX-2794.patch, PHOENIX-2794_v2.patch
>
>
> The following query:
> {code}
> SELECT TRUNC(ts,'HOUR'), AVG(avg_val)
> FROM (SELECT AVG(val),ts FROM T GROUP BY ts)
> GROUP BY TRUNC(ts,'HOUR');
> {code}
> will run much more efficiently if flattened so that the hourly bucketing is
> done on the server-side like this:
> {code}
> SELECT TRUNC(ts,'HOUR'), AVG(val)
> FROM T
> GROUP BY TRUNC(ts,'HOUR');
> {code}
> We should flatten when possible. Not sure what the general rule is, but
> perhaps if the inner and outer aggregate function matches, you can always do
> this? Maybe only for some aggregate functions like SUM, MIN, MAX, AVG?
> This comes up in time series queries in particular.
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