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https://issues.apache.org/jira/browse/HIVE-5358?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13778898#comment-13778898
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Ashutosh Chauhan commented on HIVE-5358:
----------------------------------------
For queries like:
{code}
select key, value from (select key, value from src group by key, value) t order
by value, key;
select key, value from (select key, value from src order by key, value) t group
by value, key;
{code}
In these case also two RSs can be merged but order of key Columns on RS becomes
important and must be preserved. Can you add a test case for this to make sure
this works correctly.
For queries like:
{code}
set hive.optimize.correlation=true;
select key, value from (select s1.key, s2.value from src s1 join src s2 on
s1.key = s2.key and s1.value=s2.value) t group by key,value;
select key, value from (select s1.key, s2.value from src s1 join src s2 on
s1.key = s2.key and s1.value=s2.value) t group by value,key;
{code}
For these cases also, ordering of key columns in RS is important.
cc: [~navis] [~yhuai]
> ReduceSinkDeDuplication should ignore column orders when check overlapping
> part of keys between parent and child
> ----------------------------------------------------------------------------------------------------------------
>
> Key: HIVE-5358
> URL: https://issues.apache.org/jira/browse/HIVE-5358
> Project: Hive
> Issue Type: Improvement
> Components: Query Processor
> Reporter: Chun Chen
> Assignee: Chun Chen
> Attachments: D13113.1.patch, HIVE-5358.2.patch, HIVE-5358.patch
>
>
> {code}
> select key, value from (select key, value from src group by key, value) t
> group by key, value;
> {code}
> This can be optimized by ReduceSinkDeDuplication
> {code}
> select key, value from (select key, value from src group by key, value) t
> group by value, key;
> {code}
> However the sql above can't be optimized by ReduceSinkDeDuplication currently
> due to different column orders of parent and child operator.
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