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https://issues.apache.org/jira/browse/IMPALA-6140?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lars Volker updated IMPALA-6140:
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Labels: profile (was: )
> Unexplained gap between "All backends started" and "Rows available"
> -------------------------------------------------------------------
>
> Key: IMPALA-6140
> URL: https://issues.apache.org/jira/browse/IMPALA-6140
> Project: IMPALA
> Issue Type: Bug
> Components: Distributed Exec
> Affects Versions: Impala 2.10.0
> Reporter: Tim Armstrong
> Priority: Major
> Labels: profile
>
> In the query timeline below there is a significant delay before rows are
> available.
> {noformat}
> Query Timeline
> Query submitted: 305.17us (305173)
> Planning finished: 81ms (81195593)
> Submit for admission: 82ms (82781362)
> Completed admission: 83ms (83014912)
> Ready to start on 35 backends: 84ms (84726950)
> All 35 execution backends (35 fragment instances) started: 327ms
> (327067351)
> Rows available: 1.0m (60347008871)
> Unregister query: 7.5m (447851216220)
> {noformat}
> The exec summary doesn't have any evidence of slowness. I also looked at the
> rest of the profile and couldn't find any timers > 5s.
> {noformat}
> Operator #Hosts Avg Time Max Time #Rows Est. #Rows Peak Mem
> Est. Peak Mem Detail
> ------------------------------------------------------------------------------------------------------------------
> 03:AGGREGATE 1 0.000ns 0.000ns 0 1 148.00 KB
> 10.00 MB FINALIZE
> 02:EXCHANGE 1 474.937ms 474.937ms 33 1 0
> 0 UNPARTITIONED
> 01:AGGREGATE 34 64.749ms 453.860ms 33 1 1.24 MB
> 10.00 MB
> 00:SCAN HDFS 34 1s391ms 5s736ms 987.15K 12.96B 82.19 MB
> 176.00 MB db.table
> {noformat}
> One interesting data point is that we have anecdotal evidence that there were
> orphaned query fragments sending reports on this cluster.
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