[jira] [Commented] (CASSANDRA-11053) COPY FROM on large datasets: fix progress report and debug performance

["Stefania (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-11053?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15127864#comment-15127864 ] 

Stefania commented on CASSANDRA-11053:
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Reading from standard input and parameters like {{maxrows}} and {{skiprows}} also become problematic. {{skiprows}} can be relative to a file but {{maxrows}}, as well as other max parameters, would require synchronization across processes.



> COPY FROM on large datasets: fix progress report and debug performance
> ----------------------------------------------------------------------
>
>                 Key: CASSANDRA-11053
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11053
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Tools
>            Reporter: Stefania
>            Assignee: Stefania
>             Fix For: 2.1.x, 2.2.x, 3.0.x, 3.x
>
>         Attachments: copy_from_large_benchmark.txt, parent_profile.txt, worker_profiles.txt
>
>
> Running COPY from on a large dataset (20G divided in 20M records) revealed two issues:
> * The progress report is incorrect, it is very slow until almost the end of the test at which point it catches up extremely quickly.
> * The performance in rows per second is similar to running smaller tests with a smaller cluster locally (approx 35,000 rows per second). As a comparison, cassandra-stress manages 50,000 rows per second under the same set-up, therefore resulting 1.5 times faster. 
> See attached file _copy_from_large_benchmark.txt_ for the benchmark details.



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