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https://issues.apache.org/jira/browse/IOTDB-803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17191593#comment-17191593
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wangyanhong commented on IOTDB-803:
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hi,i will do this
> Improve the way of applying aggregate func to same series in group by
> ---------------------------------------------------------------------
>
> Key: IOTDB-803
> URL: https://issues.apache.org/jira/browse/IOTDB-803
> Project: Apache IoTDB
> Issue Type: Improvement
> Components: Core/Engine
> Reporter: Yuan Tian
> Priority: Major
>
> Now, in group by, if we include more than one aggregate function for one
> series, we will iterate the series data as many times as the number of the
> aggregate functions.
> For example,
> select count(s1), sum(s1), avg(s1) from root.sg1.d1 group by([0, 100000),
> 10ms)
> Suppose that the batch data we get from s1 ranges from 0 to 20
> While calculating the count(s1), we will iterate the batch data from 0 to 10.
> And then while calculating sum or avg, we will reset the cursor to 0, and
> iterate the batch data again.
>
> However, we can do count, sum and avg function simutaneously in one iteration
> while will be also good for cpu cache hit ratio.
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