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https://issues.apache.org/jira/browse/DERBY-4977?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Knut Anders Hatlen updated DERBY-4977:
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Attachment: timing.sql
> XPLAIN reports negative EXECUTE_TIME for some parts of a join
> -------------------------------------------------------------
>
> Key: DERBY-4977
> URL: https://issues.apache.org/jira/browse/DERBY-4977
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.7.1.1
> Reporter: Knut Anders Hatlen
> Priority: Minor
> Attachments: timing.sql
>
>
> I see that if I execute a join against the system tables with XPLAIN and
> statistics timing enabled, some of the rows in SYSXPLAIN_RESULTSET_TIMINGS
> have negative values in the EXECUTE_TIME column.
> Here are the contents of the SYSXPLAIN_RESULTSET_TIMINGS after two runs with
> the attached repro script:
> ij> select execute_time from my_schema.sysxplain_resultset_timings;
> EXECUTE_TIME
> --------------------
> -1
> 0
> 0
> -6
> 9
> 16
> 6 rows selected
> ij> select execute_time from my_schema.sysxplain_resultset_timings;
> EXECUTE_TIME
> --------------------
> -1
> 1
> 0
> -7
> 10
> 15
> 6 rows selected
> Note the two rows with negative values in both of the examples.
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