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From "chenglei (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (PHOENIX-4618) Optimize out order-by on sort-merge-join when possible
Date Tue, 19 Mar 2019 01:32:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-4618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16795533#comment-16795533
] 

chenglei edited comment on PHOENIX-4618 at 3/19/19 1:31 AM:
------------------------------------------------------------

[~sangudi], yes , I think it is ok, it is just an optimization for  {{GroupBy.isOrderPreserving}}
,for hash grouping, {{ClientAggregatePlan.getOutputOrderBys}} return empty {{List}}.


was (Author: comnetwork):
[~sangudi], yes , I think it is ok, it is just an optimization for  {{GroupBy.isOrderPreserving}}
,for hash grouping

> Optimize out order-by on sort-merge-join when possible
> ------------------------------------------------------
>
>                 Key: PHOENIX-4618
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4618
>             Project: Phoenix
>          Issue Type: Improvement
>            Reporter: Maryann Xue
>            Assignee: Maryann Xue
>            Priority: Major
>             Fix For: 4.15.0, 5.1.0
>
>
> To do this, \{{OrderPreservingTracker}} relies solely on primary keys for inferring alignment
between order-by expressions and the input sortedness. To implement this improvement, we
need to have extra information of sortedness which supports equivalent sorted expressions.
For example,
> {code}SELECT * FROM T1 JOIN T2 ON T1.a = T2.a and T1.b = T2.b{code}
> The result of the sort-merge-join is sorted on (T1.a, T1.b) and (T2.a, T2.b) at the same
time.
> Thus, both 1)
> {code}SELECT * FROM T1 JOIN T2 ON T1.a = T2.a and T1.b = T2.b ORDER BY T1.a, T1.b{code}
> and 2)
> {code}SELECT * FROM T1 JOIN T2 ON T1.a = T2.a and T1.b = T2.b ORDER BY T2.a, T2.b{code}
> should avoid doing an extra order-by after the sort-merge-join operation.



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