MaxGekk commented on a change in pull request #28754:
URL: https://github.com/apache/spark/pull/28754#discussion_r436701067
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala
##########
@@ -420,6 +420,10 @@ object DateTimeUtils {
Instant.ofEpochSecond(secs, mos * NANOS_PER_MICROS)
}
+ def daysToInstant(daysSinceEpoch: SQLDate): Instant = {
+ Instant.ofEpochSecond(daysSinceEpoch * SECONDS_PER_DAY)
Review comment:
You assume `daysSinceEpoch ` in UTC here which is incorrect, in general
case.
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala
##########
@@ -420,6 +420,10 @@ object DateTimeUtils {
Instant.ofEpochSecond(secs, mos * NANOS_PER_MICROS)
}
+ def daysToInstant(daysSinceEpoch: SQLDate): Instant = {
+ Instant.ofEpochSecond(daysSinceEpoch * SECONDS_PER_DAY)
Review comment:
`daysSinceEpoch` is "local" days. For example: 1 day is 1970-01-02, and
in
- UTC is `Instant.ofEpochSecond(1 * SECONDS_PER_DAY)`
- `Europe/Amsterdam`
```scala
assert(LocalDateTime.of(
LocalDate.of(1970, 1, 2),
LocalTime.MIDNIGHT)
.atZone(ZoneId.of("Europe/Amsterdam"))
.toInstant.toEpochMilli / MILLIS_PER_HOUR ===
SECONDS_PER_DAY/SECONDS_PER_HOUR)
23 did not equal 24
ScalaTestFailureLocation:
org.apache.spark.sql.catalyst.util.DateTimeUtilsSuite at
(DateTimeUtilsSuite.scala:664)
Expected :24
Actual :23
```
The difference in 1 hour due to days are local.
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala
##########
@@ -420,6 +420,10 @@ object DateTimeUtils {
Instant.ofEpochSecond(secs, mos * NANOS_PER_MICROS)
}
+ def daysToInstant(daysSinceEpoch: SQLDate): Instant = {
+ Instant.ofEpochSecond(daysSinceEpoch * SECONDS_PER_DAY)
Review comment:
Catalyst's DATE type stores the number of days since 1970-01-01
independently from any time zone (NOT in UTC).
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala
##########
@@ -420,6 +420,10 @@ object DateTimeUtils {
Instant.ofEpochSecond(secs, mos * NANOS_PER_MICROS)
}
+ def daysToInstant(daysSinceEpoch: SQLDate): Instant = {
+ Instant.ofEpochSecond(daysSinceEpoch * SECONDS_PER_DAY)
Review comment:
I do believe it is not needed. To calculate average number of days, you
can just do `Math.floorDiv(sum, count)`.
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