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Posted to issues@kudu.apache.org by "Redriver (Jira)" <ji...@apache.org> on 2021/08/11 15:03:00 UTC

[jira] [Commented] (KUDU-1260) Add a test for prefetching on java scanner

    [ https://issues.apache.org/jira/browse/KUDU-1260?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17397414#comment-17397414 ] 

Redriver commented on KUDU-1260:
--------------------------------

This feature has bug. I have created a UT which has two threads: the writing thread insert data to the table, the scanning thread creates two scanners: one without prefetching, another has prefetching. Both scanner use the same snapshot_timestamp (which is obtained from writing thread) to scan data. We suppose the two scanners get the same row count, but it is not.

The problem looks to be the Deferred.chain. The callback is triggered, but the corresponding join() is missed to be notified. As a result, prefetching caused data missing.

> Add a test for prefetching on java scanner
> ------------------------------------------
>
>                 Key: KUDU-1260
>                 URL: https://issues.apache.org/jira/browse/KUDU-1260
>             Project: Kudu
>          Issue Type: Test
>          Components: client, test
>    Affects Versions: Public beta
>            Reporter: David Alves
>            Priority: Major
>
> We have a 'prefetching' feature in the java scanner which is not tested. We should add a test for it.



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