Correct return type of TIMESTAMPADD

h2/src/docsrc/help/help.csv

@@ -3673,10 +3673,9 @@ Use negative values to subtract units.
 addIntLong may be a long value when manipulating milliseconds,
 otherwise it's range is restricted to int.
 The same units as in the EXTRACT function are supported.
-DATEADD method returns a value with the same type as specified value if unit is compatible with this value.
+This method returns a value with the same type as specified value if unit is compatible with this value.
 If specified unit is a HOUR, MINUTE, SECOND, MILLISECOND, etc and value is a DATE value DATEADD returns combined TIMESTAMP.
 Units DAY, MONTH, YEAR, WEEK, etc are not allowed for TIME values.
-TIMESTAMPADD method returns a long.
 ","
 DATEADD('MONTH', 1, DATE '2001-01-31')
 "

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

@@ -346,7 +346,7 @@ public class Function extends Expression implements FunctionCall {
         addFunction("DATEADD", DATE_ADD,
                 3, Value.TIMESTAMP);
         addFunction("TIMESTAMPADD", DATE_ADD,
-                3, Value.LONG);
+                3, Value.TIMESTAMP);
         addFunction("DATEDIFF", DATE_DIFF,
                 3, Value.LONG);
         addFunction("TIMESTAMPDIFF", DATE_DIFF,

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

@@ -125,3 +125,9 @@ SELECT DATEADD('DAY', 10, TIMESTAMP WITH TIME ZONE '2000-01-05 15:00:30.12345678
 > -----------------------------------------------------------
 > 2000-01-15 15:00:30.123456789-10
 > rows: 1
+
+SELECT TIMESTAMPADD('DAY', 10, TIMESTAMP '2000-01-05 15:00:30.123456789');
+> TIMESTAMP '2000-01-15 15:00:30.123456789'
+> -----------------------------------------
+> 2000-01-15 15:00:30.123456789
+> rows: 1