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https://issues.apache.org/jira/browse/IMPALA-7557?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Csaba Ringhofer resolved IMPALA-7557.
-------------------------------------
    Resolution: Done

> Optimize local time functions for the UTC case
> ----------------------------------------------
>
>                 Key: IMPALA-7557
>                 URL: https://issues.apache.org/jira/browse/IMPALA-7557
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>            Reporter: Csaba Ringhofer
>            Priority: Minor
>              Labels: timestamp, timezone
>
> Currently two flags decide whether to do UTZ->local timezone conversions
> - convert_legacy_hive_parquet_utc_timestamps
> - use_local_tz_for_unix_timestamp_conversions
> Enabling these global flags make Impala more compatible with Hive, but can 
> highly degrade performance. Since IMPALA-7362, it is possible to override the 
> local timezone with a query option. Setting timezone to UTC practically 
> disables the flags above, but their overhead does not disappear completely. 
> It would be relatively easy to create shortcuts for the UTC case to avoid 
> this overhead.
> This could make it easier to choose the right values for the flags: both 
> could be set to true, and users who want to avoid the performance impact 
> could switch to UTC.



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