TimestampWithTimezone doesnt take into account Timezone to calculate hash

[kgpai]

Currently TimestampWithTimezone doesnt take into account timezone : https://github.com/prestodb/presto/blob/master/presto-common/src/main/java/com/facebook/presto/common/type/TimestampWithTimeZoneType.java#L53 , and

presto/presto-common/src/main/java/com/facebook/presto/common/type/DateTimeEncoding.java

Line 50 in a8fa57f

public static long unpackMillisUtc(long dateTimeWithTimeZone)

.
This might give similar results for different timezones.

[mbasmanova]

CC: @tdcmeehan @highker @mayankgarg1990 Tim, James, Mayank, are you aware of this limitation? Would it make sense to fix it?

[mbasmanova]

The impact of this is that checksum over timestamp with time zone column doesn't account for timezone part, hence, produces same results for two columns that differ only in time zones.