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https://issues.apache.org/jira/browse/HIVE-5056?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13761640#comment-13761640
 ] 

Navis commented on HIVE-5056:
-----------------------------

{noformat}
TS1 TS2
RS1 RS2
 JOIN

TS1=a1:a2
TS2=b1:b2
JOIN=T1.a1:T2.a2:T2.b2:T2.b1
{noformat}
For MapJoin, RS1/RS2 should be removed here. Expressions of JOIN 
(T1.a1:T2.a2:T2.b2:T2.b1) based on RS1/RS2 should be rebased on TS1/TS2.

Before the patch, expressions for JOIN is remade by iterating columns of 
TS1/TS2 and old expressions are just used for checking existence, like this
{noformat}
for (pos = 0; pos < newParentOps.size(); pos++) {
    Map<String, ExprNodeDesc> colExprMap = op.getColumnExprMap();
    for (Map.Entry<Byte, List<ExprNodeDesc>> entry : valueExprs.entrySet()) {
{noformat}

And that may change the order. In this case, "T1.a1:T2.a2:T2.b2:T2.b1" is 
changed to "T1.a1:T2.a2:T2.b1:T2.b2"
                
> MapJoinProcessor ignores order of values in removing RS
> -------------------------------------------------------
>
>                 Key: HIVE-5056
>                 URL: https://issues.apache.org/jira/browse/HIVE-5056
>             Project: Hive
>          Issue Type: Bug
>          Components: Query Processor
>            Reporter: Navis
>            Assignee: Navis
>         Attachments: HIVE-5056.D12147.1.patch, HIVE-5056.D12147.2.patch
>
>
> http://www.mail-archive.com/user@hive.apache.org/msg09073.html

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