MaxGekk commented on a change in pull request #28687:
URL: https://github.com/apache/spark/pull/28687#discussion_r432981702
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File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/HiveResult.scala
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@@ -73,7 +73,13 @@ object HiveResult {
}
private def zoneId =
DateTimeUtils.getZoneId(SQLConf.get.sessionLocalTimeZone)
- private def dateFormatter = DateFormatter(zoneId)
+ // Date formatting does not depend on time zone ID because it converts local
days
+ // since the epoch to local date string. Time zone id does matter only in
parsing
+ // when the parser has to handle special values like `now`, `yesterday` and
etc.
+ // Here, `dateFormatter` is used only for formatting, so, we can initialize
it by
+ // any time zone once, for instance, by the current session time zone. And
we can
+ // reuse it even when the session time zone might be changed.
+ private val dateFormatter = DateFormatter(zoneId)
Review comment:
Just in case, can `hiveResultString()` or `toHiveString()` be called
from multiple threads in parallel. If so, we cannot use SimpleDateFormat here
because it is not thread-safe. In that case, dateFormatter must use
`FastDateFormat` because it is thread-safe.
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