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https://issues.apache.org/jira/browse/TRAFODION-1562?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15404914#comment-15404914
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Suresh Subbiah commented on TRAFODION-1562:
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Comment from Hans.
The OLAP function that gives us the previous row value is called LAG. Here is
an example:
select a, b, c, lag(b,1) over(partition by a order by b,c), lag(c,1)
over(partition by a order by b,c)
from (values (1,1,1), (1,2,3), (1,4,5)) T(a,b,c);
See also https://community.modeanalytics.com/sql/tutorial/sql-window-functions.
The problem is that we have not implemented LAG in Trafodion.
> Changes in query tree when the upsert command is transformed into merge
> -----------------------------------------------------------------------
>
> Key: TRAFODION-1562
> URL: https://issues.apache.org/jira/browse/TRAFODION-1562
> Project: Apache Trafodion
> Issue Type: Sub-task
> Components: sql-cmp
> Reporter: Selvaganesan Govindarajan
> Assignee: Suresh Subbiah
> Attachments: BatchUpsertTransformation.pdf
>
>
> to improve the performance as explained in the main JIRA
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