Github user adrian-wang commented on a diff in the pull request:
https://github.com/apache/spark/pull/13784#discussion_r67795207
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala
---
@@ -886,23 +886,45 @@ object DateTimeUtils {
}
/**
+ * Convert the timestamp `ts` from one timezone to another.
+ *
+ * TODO: Because of DST, the conversion between UTC and human time is
not exactly one-to-one
+ * mapping, the conversion here may return wrong result, we should make
the timestamp
+ * timezone-aware.
+ */
+ def convertTz(ts: SQLTimestamp, fromZone: TimeZone, toZone: TimeZone):
SQLTimestamp = {
+ // We always use local timezone to parse or format a timestamp
+ val localZone = threadLocalLocalTimeZone.get()
+ val utcTs = if (fromZone.getID == localZone.getID) {
+ ts
+ } else {
+ // get the human time using local time zone, that actually is in
fromZone.
+ val localTs = ts + localZone.getOffset(ts / 1000L) * 1000L // in
fromZone
+ localTs - getOffsetFromLocalMillis(localTs / 1000L, fromZone) * 1000L
+ }
+ if (toZone.getID == localZone.getID) {
+ utcTs
+ } else {
+ val localTs2 = utcTs + toZone.getOffset(utcTs / 1000L) * 1000L //
in toZone
+ // treat it as local timezone, convert to UTC (we could get the
expected human time back)
+ localTs2 - getOffsetFromLocalMillis(localTs2 / 1000L, localZone) *
1000L
+ }
+ }
+
+ /**
* Returns a timestamp of given timezone from utc timestamp, with the
same string
* representation in their timezone.
*/
def fromUTCTime(time: SQLTimestamp, timeZone: String): SQLTimestamp = {
- val tz = TimeZone.getTimeZone(timeZone)
- val offset = tz.getOffset(time / 1000L)
- time + offset * 1000L
+ convertTz(time, TimeZoneGMT, TimeZone.getTimeZone(timeZone))
--- End diff --
For `fromUTCTime`, this would result in a little bit overhead.
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