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https://issues.apache.org/jira/browse/SPARK-31359?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wenchen Fan updated SPARK-31359:
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Parent: SPARK-31404
Issue Type: Sub-task (was: Improvement)
> Speed up timestamps rebasing
> ----------------------------
>
> Key: SPARK-31359
> URL: https://issues.apache.org/jira/browse/SPARK-31359
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: Maxim Gekk
> Assignee: Maxim Gekk
> Priority: Major
> Fix For: 3.0.0
>
>
> Currently, rebasing of timestamps is performed via conversions to local
> timestamps and back to microseconds. This is CPU intensive operation which
> can be avoid by converting via pre-calculated tables per each time zone. For
> example, the below is timestamps when diffs are changed in
> America/Los_Angeles time zone for the range 0001-01-01...2100-01-01
> {code}
> 0001-01-01T00:00 diff = -2872 minutes
> 0100-03-01T00:00 diff = -1432 minutes
> 0200-03-01T00:00 diff = 7 minutes
> 0300-03-01T00:00 diff = 1447 minutes
> 0500-03-01T00:00 diff = 2887 minutes
> 0600-03-01T00:00 diff = 4327 minutes
> 0700-03-01T00:00 diff = 5767 minutes
> 0900-03-01T00:00 diff = 7207 minutes
> 1000-03-01T00:00 diff = 8647 minutes
> 1100-03-01T00:00 diff = 10087 minutes
> 1300-03-01T00:00 diff = 11527 minutes
> 1400-03-01T00:00 diff = 12967 minutes
> 1500-03-01T00:00 diff = 14407 minutes
> 1582-10-15T00:00 diff = 7 minutes
> 1883-11-18T12:22:58 diff = 0 minutes
> {code}
> It seems it is possible to build rebasing maps, and perform rebasing via the
> maps.
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