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https://issues.apache.org/jira/browse/HIVE-10907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14575843#comment-14575843
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Vikram Dixit K commented on HIVE-10907:
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[~sershe] Can you please review this? The purpose of the patch is to prevent
smb joins in cases where one of the sides would be a map side work and the
other is coming from a shuffle. This jira is a work around to stop class cast
exceptions from occurring in that case. The way to prevent this is in
ConvertJoinMapJoin code where a check is made to see if the number of reduce
sinks above the parent of the join operator is either 0 or non-zero on all
sides of the join.
a join b
Non-Kosher case:
{noformat}
| There should be either no RS left of this boundary or
there should be one or more for both sides. If that is not the case, no SMB.
RS -> Gby -> | RS -> Join ->
TS -> Filter -> | RS /
{noformat}
[~hagleitn] reviewed the patch earlier and made a comment that I addressed
(basically uncommented the code). Can you take a look and review this patch
please? This needs to go to branch-1.2 as well.
Thanks
Vikram.
> Hive on Tez: Classcast exception in some cases with SMB joins
> -------------------------------------------------------------
>
> Key: HIVE-10907
> URL: https://issues.apache.org/jira/browse/HIVE-10907
> Project: Hive
> Issue Type: Bug
> Reporter: Vikram Dixit K
> Assignee: Vikram Dixit K
> Attachments: HIVE-10907.1.patch, HIVE-10907.2.patch,
> HIVE-10907.3.patch, HIVE-10907.4.patch
>
>
> In cases where there is a mix of Map side work and reduce side work, we get a
> classcast exception because we assume homogeneity in the code. We need to fix
> this correctly. For now this is a workaround.
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