update

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala

@@ -1365,7 +1365,7 @@ abstract class CastBase extends UnaryExpression with TimeZoneAwareExpression wit
   private[this] def castToYearMonthIntervalCode(from: DataType): CastFunction = from match {
     case StringType =>
       val util = IntervalUtils.getClass.getCanonicalName.stripSuffix("$")
-      (c, evPrim, evNull) => code"$evPrim = $util.castStringToYMInterval($c);"
+      (c, evPrim, _) => code"$evPrim = $util.castStringToYMInterval($c);"
   }
 
   private[this] def decimalToTimestampCode(d: ExprValue): Block = {

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/IntervalUtils.scala

@@ -19,7 +19,6 @@ package org.apache.spark.sql.catalyst.util
 
 import java.time.{Duration, Period}
 import java.time.temporal.ChronoUnit
-import java.util.Locale
 import java.util.concurrent.TimeUnit
 
 import scala.util.control.NonFatal
@@ -94,10 +93,10 @@ object IntervalUtils {
 
   private val yearMonthPattern = "^([+|-])?(\\d+)-(\\d+)$".r
   private val yearMonthStringPattern =
-    "^(INTERVAL\\s+)([+|-])?(')([+|-])?(\\d+)-(\\d+)(')(\\s+YEAR\\s+TO\\s+MONTH)$".r
+    "(?i)^(INTERVAL\\s+)([+|-])?(')([+|-])?(\\d+)-(\\d+)(')(\\s+YEAR\\s+TO\\s+MONTH)$".r
 
   def castStringToYMInterval(input: UTF8String): Int = {
-    input.trimAll().toString.toUpperCase(Locale.ROOT) match {
+    input.trimAll().toString match {
       case yearMonthPattern("-", year, month) => toYMInterval(year, month, -1)
       case yearMonthPattern(_, year, month) => toYMInterval(year, month, 1)
       case yearMonthStringPattern(_, firstSign, _, secondSign, year, month, _, _) =>

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala

@@ -1788,6 +1788,9 @@ class CastSuite extends CastSuiteBase {
       YearMonthIntervalType), 12)
     checkEvaluation(cast(Literal.create("INTERVAL +'1-0' YEAR TO MONTH"),
       YearMonthIntervalType), 12)
+    checkEvaluation(cast(Literal.create(" interval +'1-0' YEAR  TO MONTH "),
+      YearMonthIntervalType), 12)
+    checkEvaluation(cast(Literal.create(" -1-0 "), YearMonthIntervalType), -12)
     checkEvaluation(cast(Literal.create("-1-0"), YearMonthIntervalType), -12)
     checkEvaluation(cast(Literal.create(null, StringType), YearMonthIntervalType), null)