[GitHub] [spark] jerrypeng commented on a diff in pull request #36737: [SPARK-39347] [SS] Generate wrong time window when (timestamp-startTime) % slideDuration…

[GitBox <gi...@apache.org>]

jerrypeng commented on code in PR #36737:
URL: https://github.com/apache/spark/pull/36737#discussion_r891532480


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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:
   Can you explain why this is correct now?  Please give an example.



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