SUM on a boolean expression will now count the number of 'true' rows.

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

@@ -395,10 +395,14 @@ public class Aggregate extends Expression {
             precision = displaySize = Integer.MAX_VALUE;
             break;
         case SUM:
-            if (!DataType.supportsAdd(dataType)) {
+            if (dataType == Value.BOOLEAN) {
+                // example: sum(id > 3) (count the rows)
+                dataType = Value.LONG;
+            } else if (!DataType.supportsAdd(dataType)) {
                 throw DbException.get(ErrorCode.SUM_OR_AVG_ON_WRONG_DATATYPE_1, getSQL());
+            } else {
+                dataType = DataType.getAddProofType(dataType);
             }
-            dataType = DataType.getAddProofType(dataType);
             break;
         case AVG:
             if (!DataType.supportsAdd(dataType)) {

h2/src/test/org/h2/test/testSimple.in.txt

+select sum(mod(x, 2) = 1) from system_range(1, 10);
+> 5;
 create table a(x int);
 create table b(x int);
 select count(*) from (select b.x from a left join b);