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Posted to reviews@spark.apache.org by GitBox <gi...@apache.org> on 2019/10/16 09:22:58 UTC
[GitHub] [spark] MaxGekk commented on issue #26134: [SPARK-29486][SQL]
CalendarInterval should have 3 fields: months, days and microseconds
MaxGekk commented on issue #26134: [SPARK-29486][SQL] CalendarInterval should have 3 fields: months, days and microseconds
URL: https://github.com/apache/spark/pull/26134#issuecomment-542611504
> Why are the changes needed?
> One logical day interval may have different number of microseconds (daylight saving).
For example, in PST timezone, there will be 25 hours from 2019-11-2 12:00:00 to
2019-11-3 12:00:00
Yes, actual duration of the daylight saving day can be 25 hours but logically any day has 24 hours. Spark `INTERVAL` type defines not duration, it is adjustment of local date-time. After your changes, it adjusts logical (local) months, days and for some reasons physical time duration of a day. It looks like inconsistent, doesn't it?
As you point out, the daylight saving in PST will happen at `2019-11-03 02:00:00`. So, the next timestamp with granularity of 1 microsecond is `2019-11-03 01:00:01`. Even more, the local timestamp `2019-11-03 02:00:00` will be showed on local clock twice.
At the first time:
```
timestamp'2019-11-03 02:00:00' + interval 1 microsecond = timestamp'2019-11-03 01:00:00.000001'
```
At the second time:
```
timestamp'2019-11-03 02:00:00' + interval 1 microsecond = timestamp'2019-11-03 02:00:00.000001'
```
Could you elaborate how your changes resolve this situation?
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