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https://issues.apache.org/jira/browse/HIVE-21197?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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mahesh kumar behera reassigned HIVE-21197:
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> Hive Replication can add duplicate data during migration from 3.0 to 4
> ----------------------------------------------------------------------
>
> Key: HIVE-21197
> URL: https://issues.apache.org/jira/browse/HIVE-21197
> Project: Hive
> Issue Type: Task
> Components: repl
> Reporter: mahesh kumar behera
> Assignee: mahesh kumar behera
> Priority: Major
>
> During bootstrap phase it may happen that the files copied to target are
> created by events which are not part of the bootstrap. This is because of the
> fact that, bootstrap first gets the last event id and then the file list. So
> during this period if some event happens, then bootstrap will include files
> created by these events also. So the same files will be copied again during
> the first incremental replication just after the bootstrap. In normal
> scenario, the duplicate copy does not cause any issue as hive allows the use
> of target database only after the first incremental. But in case of
> migration, the file at source and target are copied to different location
> (based on the write id at target) and thus this may lead to duplicate data at
> target. This can be avoided by having at check at load time for duplicate
> file. This check can be done only for the first incremental and the search
> can be done in the bootstrap directory (with write id 1). if the file is
> already present then just ignore the copy.
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