nyingping commented on code in PR #36737:
URL: https://github.com/apache/spark/pull/36737#discussion_r891847061
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala:
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@@ -3963,8 +3966,10 @@ object TimeWindowing extends Rule[LogicalPlan] {
def getWindow(i: Int, dataType: DataType): Expression = {
val timestamp = PreciseTimestampConversion(window.timeColumn,
dataType, LongType)
- val lastStart = timestamp - (timestamp - window.startTime
- + window.slideDuration) % window.slideDuration
+ val remainder = (timestamp - window.startTime) % window.slideDuration
+ val lastStart = CaseWhen(
+ Seq((LessThan(remainder, 0), timestamp - remainder -
window.slideDuration))
Review Comment:
Thank you for reviewing.
For any event timestamp, the start time of the last window (whether tumbling
or sliding) obtained by it should always be less than the current timestamp.
When `(timestamp - window.starttime)% window.slideduration <0`, the obtained
laststart will be greater than timestamp. At this time, it is necessary to
shift the window to the right, which is the correct laststart value.
For example
code
```
val timestamp = -13
val offset = 0
val windowSize = 7
// old code
val lastStartOld = timestamp - (timestamp - offset - windowSize) %
windowSize
// new code
val remainder = (timestamp - offset) % windowSize
val lastStartNew =
if (remainder < 0) {
timestamp - remainder - windowSize
} else {
timestamp - remainder - windowSize
}
println(s"lastStartOld = $lastStartOld lastStartNew = $lastStartNew")
```
result
```
lastStartOld = -7 lastStartNew = -14
```
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