fix: Date_add throws or produces wrong results when the result would be nonexistent time in the time zone #11845
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…be nonexistent time in the time zone (facebookincubator#11845) Summary: Date_add is computed on top of Unix timestamps (millis since epoch). When the unit being added is at least a day, this calculation is done in the "local" time zone (the session time zone in the case of Timestamps and the time zone associated with the value in the case of TImestampWithTimeZones). This local time is then converted back to a system time. When this calculation is done in a "local" time zone, the resulting local millis since epoch may not exist, e.g. in U.S. time zones that respect daylight savings time, it may fall in the hour 2:00-3:00 am on the day when the clocks move forward. In this case, date_add will throw an exception when this is done with Timestamps, and return the next valid time (e.g. 3 am in the example above) when this is done with TimestampWithTimeZones. To fix this I added a function correct_nonexistent_time to TimeZoneMap which can take a local timestamp and adjust it by the difference between the to time zones (e.g. moves it forward an hour in the case of the example above) and returns a timestamp that exists. This gets us behavior that is consistent with Presto Java. Differential Revision: D67154813
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This pull request was exported from Phabricator. Differential Revision: D67154813 |
HeidiHan0000
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Summary:
Date_add is computed on top of Unix timestamps (millis since epoch). When the unit being added is at least a
day, this calculation is done in the "local" time zone (the session time zone in the case of Timestamps and the
time zone associated with the value in the case of TImestampWithTimeZones). This local time is then converted
back to a system time.
When this calculation is done in a "local" time zone, the resulting local millis since epoch may not exist, e.g. in
U.S. time zones that respect daylight savings time, it may fall in the hour 2:00-3:00 am on the day when the
clocks move forward. In this case, date_add will throw an exception when this is done with Timestamps, and
return the next valid time (e.g. 3 am in the example above) when this is done with TimestampWithTimeZones.
To fix this I added a function correct_nonexistent_time to TimeZoneMap which can take a local timestamp and
adjust it by the difference between the to time zones (e.g. moves it forward an hour in the case of the example
above) and returns a timestamp that exists. This gets us behavior that is consistent with Presto Java.
Differential Revision: D67154813