refractor the code to a function in DateTimeUtils

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

@@ -1506,26 +1506,11 @@ public class Function extends Expression implements FunctionCall {
             // Case where the date has to be truncated to the day.
             if (fieldValue.equals("DAY")) {
 
-                if (v1 instanceof ValueTimestampTimeZone) {
-
-                    // Create a new ValueTimestampTimeZone by only setting the
-                    // date. The time in nanoseconds since midnight will be set
-                    // to 0.
-                    ValueTimestampTimeZone v = (ValueTimestampTimeZone) v1;
-                    result = ValueTimestampTimeZone.fromDateValueAndNanos(v.getDateValue(), 0,
-                            v.getTimeZoneOffsetMins());
-
-                } else {
-
-                    // By default, we create a timestamp by setting the
-                    // datevalue
-                    // to the datevalue retrieved and the time in nanoseconds
-                    // since midnight to 0.
-                    result = ValueTimestamp.fromDateValueAndNanos(fieldDateValue, 0);
-                }
+                result = DateTimeUtils.truncateToDay(v1, fieldDateValue);
 
             } else {
 
+                // Return an exception for the other possible value (not yet supported).
                 throw DbException.getUnsupportedException(v0.getString());
             }
             break;

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

@@ -1470,5 +1470,35 @@ public class DateTimeUtils {
         }
         return nanosOfDay - mod;
     }
+    
+    /**
+     * Truncate the given date to 'day'
+     * 
+     * @param value the date
+     * @param dateValue the dateValue used if the value is not a timestamp time
+     *            zone
+     * @return date truncated to 'day'
+     */
+    public static Value truncateToDay(Value value, long dateValue) {
+        Value result = null;
+
+        if (value instanceof ValueTimestampTimeZone) {
+
+            // Create a new ValueTimestampTimeZone by only setting the
+            // date. The time in nanoseconds since midnight will be set
+            // to 0.
+            ValueTimestampTimeZone vTmp = (ValueTimestampTimeZone) value;
+            result = ValueTimestampTimeZone.fromDateValueAndNanos(vTmp.getDateValue(), 0, vTmp.getTimeZoneOffsetMins());
+
+        } else {
+
+            // By default, we create a timestamp by setting the
+            // datevalue to the datevalue retrieved and the time in nanoseconds
+            // since midnight to 0.
+            result = ValueTimestamp.fromDateValueAndNanos(dateValue, 0);
+        }
+
+        return result;
+    }
 
 }