address comment

Author: cloud-fan

common/unsafe/src/main/java/org/apache/spark/unsafe/types/CalendarInterval.java

@@ -84,27 +84,29 @@ public int hashCode() {
 
   @Override
   public String toString() {
+    if (months == 0 && days == 0 && microseconds == 0) {
+      return "0 seconds";
+    }
+
     StringBuilder sb = new StringBuilder();
 
     if (months != 0) {
-      appendUnit(sb, months / 12, "year");
-      appendUnit(sb, months % 12, "month");
+      appendUnit(sb, months / 12, "years");
+      appendUnit(sb, months % 12, "months");
     }
 
-    appendUnit(sb, days, "day");
+    appendUnit(sb, days, "days");
 
     if (microseconds != 0) {
       long rest = microseconds;
-      appendUnit(sb, rest / MICROS_PER_HOUR, "hour");
+      appendUnit(sb, rest / MICROS_PER_HOUR, "hours");
       rest %= MICROS_PER_HOUR;
-      appendUnit(sb, rest / MICROS_PER_MINUTE, "minute");
+      appendUnit(sb, rest / MICROS_PER_MINUTE, "minutes");
       rest %= MICROS_PER_MINUTE;
       if (rest != 0) {
         String s = BigDecimal.valueOf(rest, 6).stripTrailingZeros().toPlainString();
         sb.append(s).append(" seconds ");
       }
-    } else if (months == 0 && days == 0) {
-      sb.append("0 microseconds ");
     }
 
     sb.setLength(sb.length() - 1);
@@ -113,7 +115,7 @@ public String toString() {
 
   private void appendUnit(StringBuilder sb, long value, String unit) {
     if (value != 0) {
-      sb.append(value).append(' ').append(unit).append('s').append(' ');
+      sb.append(value).append(' ').append(unit).append(' ');
     }
   }
 

common/unsafe/src/test/java/org/apache/spark/unsafe/types/CalendarIntervalSuite.java

@@ -51,7 +51,7 @@ public void toStringTest() {
     CalendarInterval i;
 
     i = new CalendarInterval(0, 0, 0);
-    assertEquals("0 microseconds", i.toString());
+    assertEquals("0 seconds", i.toString());
 
     i = new CalendarInterval(34, 0, 0);
     assertEquals("2 years 10 months", i.toString());

docs/sql-migration-guide.md

@@ -220,6 +220,8 @@ license: |
 
   - Since Spark 3.0, the interval literal syntax does not allow multiple from-to units anymore. For example, `SELECT INTERVAL '1-1' YEAR TO MONTH '2-2' YEAR TO MONTH'` throws parser exception.
 
+  - Since Spark 3.0, when casting interval values to string type, there is no "interval" prefix, e.g. `1 days 2 hours`. In Spark version 2.4 and earlier, the string contains the "interval" prefix like `interval 1 days 2 hours`.
+
 ## Upgrading from Spark SQL 2.4 to 2.4.1
 
   - The value of `spark.executor.heartbeatInterval`, when specified without units like "30" rather than "30s", was