Add a comment

apache · Apr 19, 2021 · 68c36d1 · 68c36d1
1 parent 2424d6b
commit 68c36d1
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
@@ -2315,6 +2315,10 @@ class AstBuilder extends SqlBaseBaseVisitor[AnyRef] with SQLConfHelper with Logg
   override def visitInterval(ctx: IntervalContext): Literal = withOrigin(ctx) {
     val calendarInterval = parseIntervalLiteral(ctx)
     if (ctx.errorCapturingUnitToUnitInterval != null && !conf.legacyIntervalEnabled) {
+      // Check the `to` unit to distinguish year-month and day-time intervals because
+      // `CalendarInterval` doesn't have enough info. For instance, new CalendarInterval(0, 0, 0)
+      // can be derived from INTERVAL '0-0' YEAR TO MONTH as well as from
+      // INTERVAL '0 00:00:00' DAY TO SECOND.
       val toUnit = ctx.errorCapturingUnitToUnitInterval.body.to.getText.toLowerCase(Locale.ROOT)
       if (toUnit == "month") {
         assert(calendarInterval.days == 0 && calendarInterval.microseconds == 0)