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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HIVE-8435) Add identity project remover optimization
Date Sun, 12 Oct 2014 22:49:33 GMT

    [ https://issues.apache.org/jira/browse/HIVE-8435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14168829#comment-14168829
] 

Ashutosh Chauhan edited comment on HIVE-8435 at 10/12/14 10:48 PM:
-------------------------------------------------------------------

 This optimization tries to remove SelectOperator from operator tree which don't do any processing
except forwarding columns from its parent to its children.e.g., 
{code} 
select * from (select * from src where key = value) t1 join (select * from src where key =
value) t2;
{code}
{noformat}
 Query tree
   Without this optimization:
   TS -> FIL -> SEL -> RS ->
                                             JOIN -> SEL -> FS
   TS -> FIL -> SEL -> RS ->

  With this optimization
  TS -> FIL -> RS ->
                                JOIN -> FS
  TS -> FIL -> RS ->
 {noformat}
 Note absence of select operator after filter and after join operator.



was (Author: ashutoshc):
 This optimization tries to remove SelectOperator from operator tree which don't do any processing
except forwarding columns from its parent to its children.e.g., 
{code} 
select * from (select * from src where key = value) t1 join (select * from src where key =
value) t2;
{code}
 Query tree
   Without this optimization:
   TS -> FIL -> SEL -> RS ->
                                             JOIN -> SEL -> FS
   TS -> FIL -> SEL -> RS ->

  With this optimization
  TS -> FIL -> RS ->
                                JOIN -> FS
  TS -> FIL -> RS ->
 
 Note absence of select operator after filter and after join operator.


> Add identity project remover optimization
> -----------------------------------------
>
>                 Key: HIVE-8435
>                 URL: https://issues.apache.org/jira/browse/HIVE-8435
>             Project: Hive
>          Issue Type: New Feature
>          Components: Logical Optimizer
>    Affects Versions: 0.9.0, 0.10.0, 0.11.0, 0.12.0, 0.13.0
>            Reporter: Ashutosh Chauhan
>            Assignee: Ashutosh Chauhan
>         Attachments: HIVE-8435.patch
>
>
> In some cases there is an identity project in plan which is useless. Better to optimize
it away to avoid evaluating it without any benefit at runtime.



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