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https://issues.apache.org/jira/browse/HIVE-7469?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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wangmeng updated HIVE-7469:
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    Description: 
In https://issues.apache.org/jira/browse/HIVE-964, I  have a  general   idea 
about how to  deal with skew join key , the key is that  use mapjoin to deal 
with skew key, but there has a case  which troubles me:
if the two join tables  have the same big skew key on one value :
for example , select *  from  table A join B  on  A.id=b.id,  both table A  and 
B  have  a lot of  keys on id=1,  in  this  case , if we  use map join  to deal 
with   the skew key  id=1  ,maybe it    will OOM.
so ,how  to fix this  case?  Will  it  rollback  to common  join ? Thanks.

  was:
In https://issues.apache.org/jira/browse/HIVE-964, I  have a  general   idea 
about how to  deal with skew join key ,but there has a case  which troubles me:
if the two join tables  have the same big skew key on one value :
for example , select *  from  table A join B  on  A.id=b.id,  both table A  and 
B  have  a lot of  keys on id=1,  in  this  case , if we  use map join  to deal 
with   the skew key  id=1  ,maybe it    will OOM.
so ,how  to fix this  case?  Will  it  rollback  to common  join ? Thanks.


> skew join keys  when  two join  table  have the same big skew key
> -----------------------------------------------------------------
>
>                 Key: HIVE-7469
>                 URL: https://issues.apache.org/jira/browse/HIVE-7469
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: wangmeng
>
> In https://issues.apache.org/jira/browse/HIVE-964, I  have a  general   idea 
> about how to  deal with skew join key , the key is that  use mapjoin to deal 
> with skew key, but there has a case  which troubles me:
> if the two join tables  have the same big skew key on one value :
> for example , select *  from  table A join B  on  A.id=b.id,  both table A  
> and B  have  a lot of  keys on id=1,  in  this  case , if we  use map join  
> to deal with   the skew key  id=1  ,maybe it    will OOM.
> so ,how  to fix this  case?  Will  it  rollback  to common  join ? Thanks.



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