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From "Prasanth J (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-5817) column name to index mapping in VectorizationContext is broken
Date Mon, 25 Nov 2013 21:58:36 GMT

    [ https://issues.apache.org/jira/browse/HIVE-5817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13831960#comment-13831960
] 

Prasanth J commented on HIVE-5817:
----------------------------------

I came across this exact same issue (column name collision) when I worked on HIVE-5369. As
Ashutosh pointed out tabAlias.colName will work. This is what I am using for resolving column
names from different parent operators. Reference code can be found in JoinStatsRule under
StatsRulesProcFactory.java.
Another option is every operator will have output row schema which has list of ColumnInfo.
ColumnInfo internally contains internal column name and table alias, when used as a key for
hashmap should avoid column name collision. Hope this helps.

> column name to index mapping in VectorizationContext is broken
> --------------------------------------------------------------
>
>                 Key: HIVE-5817
>                 URL: https://issues.apache.org/jira/browse/HIVE-5817
>             Project: Hive
>          Issue Type: Bug
>          Components: Vectorization
>            Reporter: Sergey Shelukhin
>            Assignee: Remus Rusanu
>            Priority: Critical
>         Attachments: HIVE-5817-uniquecols.broken.patch, HIVE-5817.00-broken.patch, HIVE-5817.4.patch
>
>
> Columns coming from different operators may have the same internal names ("_colNN").
There exists a query in the form {{select b.cb, a.ca from a JOIN b ON ... JOIN x ON ...;}}
 (distilled from a more complex query), which runs ok w/o vectorization. With vectorization,
it will run ok for most ca, but for some ca it will fail (or can probably return incorrect
results). That is because when building column-to-VRG-index map in VectorizationContext, internal
column name for ca that the first map join operator adds to the mapping may be the same as
internal name for cb that the 2nd one tries to add. 2nd VMJ doesn't add it (see code in ctor),
and when it's time for it to output stuff, it retrieves wrong index from the map by name,
and then wrong vector from VRG.



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