[GitHub] [spark] srowen commented on a change in pull request #26079: [SPARK-29369][SQL] Support string intervals without the `interval` prefix

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srowen commented on a change in pull request #26079: [SPARK-29369][SQL] Support string intervals without the `interval` prefix
URL: https://github.com/apache/spark/pull/26079#discussion_r334549028
 
 

 ##########
 File path: common/unsafe/src/main/java/org/apache/spark/unsafe/types/CalendarInterval.java
 ##########
 @@ -73,45 +72,53 @@ private static long toLong(String s) {
    * This method is case-insensitive.
    */
   public static CalendarInterval fromString(String s) {
-    if (s == null) {
-      return null;
-    }
-    s = s.trim();
-    Matcher m = p.matcher(s);
-    if (!m.matches() || s.compareToIgnoreCase("interval") == 0) {
+    try {
+      return fromCaseInsensitiveString(s);
+    } catch (IllegalArgumentException e) {
       return null;
-    } else {
-      long months = toLong(m.group(1)) * 12 + toLong(m.group(2));
-      long microseconds = toLong(m.group(3)) * MICROS_PER_WEEK;
-      microseconds += toLong(m.group(4)) * MICROS_PER_DAY;
-      microseconds += toLong(m.group(5)) * MICROS_PER_HOUR;
-      microseconds += toLong(m.group(6)) * MICROS_PER_MINUTE;
-      microseconds += toLong(m.group(7)) * MICROS_PER_SECOND;
-      microseconds += toLong(m.group(8)) * MICROS_PER_MILLI;
-      microseconds += toLong(m.group(9));
-      return new CalendarInterval((int) months, microseconds);
     }
   }
 
   /**
-   * Convert a string to CalendarInterval. Unlike fromString, this method can handle
+   * Convert a string to CalendarInterval. This method can handle
    * strings without the `interval` prefix and throws IllegalArgumentException
    * when the input string is not a valid interval.
    *
    * @throws IllegalArgumentException if the string is not a valid internal.
    */
   public static CalendarInterval fromCaseInsensitiveString(String s) {
-    if (s == null || s.trim().isEmpty()) {
-      throw new IllegalArgumentException("Interval cannot be null or blank.");
+    if (s == null) {
+      throw new IllegalArgumentException("Interval cannot be null");
     }
-    String sInLowerCase = s.trim().toLowerCase(Locale.ROOT);
-    String interval =
-      sInLowerCase.startsWith("interval ") ? sInLowerCase : "interval " + sInLowerCase;
-    CalendarInterval cal = fromString(interval);
-    if (cal == null) {
+    String trimmed = s.trim();
+    if (trimmed.isEmpty()) {
+      throw new IllegalArgumentException("Interval cannot be blank");
+    }
+    String prefix = "interval";
+    String intervalStr = trimmed;
+    // Checks the given interval string does not start with the `interval` prefix
+    if (!intervalStr.regionMatches(true, 0, prefix, 0, prefix.length())) {
+      // Prepend `interval` if it does not present because
+      // the regular expression strictly require it.
 
 Review comment:
   I tried simply `"(interval)?(.+)".r` and it worked as expected on inputs like `"abc"` and `"interval abc"`. It's a toy example and not sure if it interacts unexpectedly with the rest of the matching. no big deal, just leave it.

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