[GitHub] [spark] gengliangwang commented on a change in pull request #32056: [SPARK-34667][SQL] Support casting of year-month intervals to strings

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

gengliangwang commented on a change in pull request #32056:
URL: https://github.com/apache/spark/pull/32056#discussion_r607574835



##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/IntervalUtils.scala
##########
@@ -834,4 +834,21 @@ object IntervalUtils {
    * @return The period of months, not null
    */
   def monthsToPeriod(months: Int): Period = Period.ofMonths(months).normalized()
+
+  /**
+   * Converts an year-month interval as a number of months to its textual representation
+   * which conforms to the ANSI SQL standard.
+   *
+   * @param months The number of months, positive or negative
+   * @return Year-month interval string
+   */
+  def toYMIntervalString(months: Int): String = {
+    var sign = ""
+    var absMonths: Long = months
+    if (months < 0) {
+      sign = "-"
+      absMonths = -absMonths
+    }
+    s"interval '$sign${absMonths / MONTHS_PER_YEAR}-${absMonths % MONTHS_PER_YEAR}' year to month"

Review comment:
       The last part "year to month" looks a bit confusing to me.  What does other DBMS systems do?




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