Use datediff() in ADD_MONTHS and convert test to SQL form

h2/src/main/org/h2/expression/Function.java

@@ -1471,7 +1471,7 @@ public class Function extends Expression implements FunctionCall {
                     v1 == null ? null : v1.getString()));
             break;
         case ADD_MONTHS:
-            result = ValueTimestamp.get(DateTimeUtils.addMonths(v0.getTimestamp(), v1.getInt()));
+            result = dateadd("MONTH", v1.getInt(), v0);
             break;
         case TRANSLATE: {
             String matching = v1.getString();

h2/src/main/org/h2/util/DateTimeUtils.java

@@ -1222,26 +1222,6 @@ public class DateTimeUtils {
         return dateValue(y, m + 3, (int) d);
     }
 
-    /**
-     * Adds the number of months to the date. If the resulting month's number of
-     * days is less than the original's day-of-month, the resulting
-     * day-of-months gets adjusted accordingly: <br>
-     * 30.04.2007 - 2 months = 28.02.2007
-     *
-     * @param refDate the original date
-     * @param nrOfMonthsToAdd the number of months to add
-     * @return the new timestamp
-     */
-    public static Timestamp addMonths(Timestamp refDate, int nrOfMonthsToAdd) {
-        Calendar calendar = DateTimeUtils.createGregorianCalendar();
-        calendar.setTime(refDate);
-        calendar.add(Calendar.MONTH, nrOfMonthsToAdd);
-
-        Timestamp resultDate = new Timestamp(calendar.getTimeInMillis());
-        resultDate.setNanos(refDate.getNanos());
-        return resultDate;
-    }
-
     /**
      * Append a date to the string builder.
      *

h2/src/test/org/h2/test/db/TestFunctions.java

@@ -82,7 +82,6 @@ public class TestFunctions extends TestBase implements AggregateFunction {
         testIfNull();
         testToDate();
         testToDateException();
-        testAddMonths();
         testDataType();
         testVersion();
         testFunctionTable();
@@ -1428,39 +1427,6 @@ public class TestFunctions extends TestBase implements AggregateFunction {
         date.setTime(c.getTimeInMillis());
     }
 
-    private void testAddMonths() throws ParseException {
-        Timestamp date;
-        Timestamp expected;
-
-        // 01-Aug-03 + 3 months = 01-Nov-03
-        date = new Timestamp(
-                new SimpleDateFormat("yyyy-MM-dd").parse("2003-08-01").getTime());
-        expected = new Timestamp(
-                new SimpleDateFormat("yyyy-MM-dd").parse("2003-11-01").getTime());
-        assertEquals(expected, DateTimeUtils.addMonths(new Timestamp(date.getTime()), 3));
-
-        // 31-Jan-03 + 1 month = 28-Feb-2003
-        date = new Timestamp(
-                new SimpleDateFormat("yyyy-MM-dd").parse("2003-01-31").getTime());
-        expected = new Timestamp(
-                new SimpleDateFormat("yyyy-MM-dd").parse("2003-02-28").getTime());
-        assertEquals(expected, DateTimeUtils.addMonths(new Timestamp(date.getTime()), 1));
-
-        // 21-Aug-2003 - 3 months = 21-May-2003
-        date = new Timestamp(
-                new SimpleDateFormat("yyyy-MM-dd").parse("2003-08-21").getTime());
-        expected = new Timestamp(
-                new SimpleDateFormat("yyyy-MM-dd").parse("2003-05-21").getTime());
-        assertEquals(expected, DateTimeUtils.addMonths(new Timestamp(date.getTime()), -3));
-
-        // 21-Aug-2003 00:00:00:333 - 3 months = 21-May-2003 00:00:00:333
-        date = new Timestamp(
-                new SimpleDateFormat("yyyy-MM-dd SSS").parse("2003-08-21 333").getTime());
-        expected = new Timestamp(
-                new SimpleDateFormat("yyyy-MM-dd SSS").parse("2003-05-21 333").getTime());
-        assertEquals(expected, DateTimeUtils.addMonths(new Timestamp(date.getTime()), -3));
-    }
-
     private void testToCharFromDateTime() throws SQLException {
         deleteDb("functions");
         Connection conn = getConnection("functions");

h2/src/test/org/h2/test/scripts/TestScript.java

@@ -135,7 +135,7 @@ public class TestScript extends TestBase {
                 "set", "table", "transaction-id", "truncate-value", "user" }) {
             testScript("functions/system/" + s + ".sql");
         }
-        for (String s : new String[] { "current_date", "current_timestamp",
+        for (String s : new String[] { "add_months", "current_date", "current_timestamp",
                 "current-time", "dateadd", "datediff", "dayname",
                 "day-of-month", "day-of-week", "day-of-year", "extract",
                 "formatdatetime", "hour", "minute", "month", "monthname",

h2/src/test/org/h2/test/scripts/functions/timeanddate/add_months.sql

+-- Copyright 2004-2018 H2 Group. Multiple-Licensed under the MPL 2.0,
+-- and the EPL 1.0 (http://h2database.com/html/license.html).
+-- Initial Developer: H2 Group
+--
+
+-- 01-Aug-03 + 3 months = 01-Nov-03
+SELECT ADD_MONTHS('2003-08-01', 3) AS R;
+> R
+> ---------------------
+> 2003-11-01 00:00:00.0
+> rows: 1
+
+-- 31-Jan-03 + 1 month = 28-Feb-2003
+SELECT ADD_MONTHS('2003-01-31', 1) AS R;
+> R
+> ---------------------
+> 2003-02-28 00:00:00.0
+> rows: 1
+
+-- 21-Aug-2003 - 3 months = 21-May-2003
+SELECT ADD_MONTHS('2003-08-21', -3) AS R;
+> R
+> ---------------------
+> 2003-05-21 00:00:00.0
+> rows: 1
+
+-- 21-Aug-2003 00:00:00.333 - 3 months = 21-May-2003 00:00:00.333
+SELECT ADD_MONTHS('2003-08-21 00:00:00.333', -3) AS R;
+> R
+> -----------------------
+> 2003-05-21 00:00:00.333
+> rows: 1