[jira] [Commented] (IOTDB-514) To support aggregation in the distributed version

["Yuxin Zhang (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IOTDB-514?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17043464#comment-17043464 ] 

Yuxin Zhang commented on IOTDB-514:
-----------------------------------

hi, I'm fixing this issue.

> To support aggregation in the distributed version
> -------------------------------------------------
>
>                 Key: IOTDB-514
>                 URL: https://issues.apache.org/jira/browse/IOTDB-514
>             Project: Apache IoTDB
>          Issue Type: Improvement
>            Reporter: Tian Jiang
>            Priority: Major
>              Labels: aggregation, distributed, query
>             Fix For: master branch
>
>
> The current aggregation cannot satisfy the needs in the distributed version, to be specific, there are two points that should be satisfied:
> 1. The FirstValueAggrResult and LastValueAggrResult should also contain timestamp.
> Without a timestamp, the coordinator node cannot tell the result from which node is the true first/last.
> 2. An AggrResult should be able to merge with another. When we get AggrResults from all nodes that participate in the query, these results should be merged to generate a new result.
> To resolve the issue, you should:
> 1. Add a field `timestamp` in FirstValueAggrResult and LastValueAggrResult
> 2. Add an abstract method `merge(AggregateResult another)` in AggregateResult and implement it properly.



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