[jira] [Created] (HIVE-21197) Hive Replication can add duplicate data during migration from 3.0 to 4

["mahesh kumar behera (JIRA)" <ji...@apache.org>]

mahesh kumar behera created HIVE-21197:
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             Summary: 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


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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