Union queries: duplicate rows could be returned if the sub-queries contained "order by".

h2/src/docsrc/html/changelog.html

@@ -18,7 +18,8 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>The GEOMETRY data type now works for user defined functions that return a result set.
+<ul><li>Union queries: duplicate rows could be returned if the sub-queries contained "order by".
+</li><li>The GEOMETRY data type now works for user defined functions that return a result set.
 </li><li>PostgreSQL compatibility: the PgServer was not working properly when the setting
     database_to_upper was set to false.
 </li><li>JdbcDataSource: the methods setUrl and getUrl where added as aliases for setURL and getURL.

h2/src/main/org/h2/command/dml/SelectUnion.java

@@ -103,11 +103,20 @@ public class SelectUnion extends Query {
     }
 
     private Value[] convert(Value[] values, int columnCount) {
+        Value[] newValues;
+        if (columnCount == values.length) {
+            // re-use the array if possible
+            newValues = values;
+        } else {
+            // create a new array if needed,
+            // for the value hash set
+            newValues = new Value[columnCount];
+        }
         for (int i = 0; i < columnCount; i++) {
             Expression e = expressions.get(i);
-            values[i] = values[i].convertTo(e.getType());
+            newValues[i] = values[i].convertTo(e.getType());
         }
-        return values;
+        return newValues;
     }
 
     @Override

h2/src/test/org/h2/test/testScript.sql

@@ -4,6 +4,18 @@
 -- Initial Developer: H2 Group
 --
 --- special grammar and test cases ---------------------------------------------------------------------------------------------
+create table test(id int, name varchar) as select 1, 'a';
+> ok
+
+(select id from test order by id) union (select id from test order by name);
+> ID
+> --
+> 1
+> rows (ordered): 1
+
+drop table test;
+> ok
+
 create sequence seq;
 > ok
 
@@ -1334,8 +1346,7 @@ drop table p;
 > X
 > -
 > 1
-> 1
-> rows (ordered): 2
+> rows (ordered): 1
 
 create table test(a int, b int default 1);
 > ok