Foreign key: don't add a single column index if column is leading key of existing index.

h2/src/docsrc/html/changelog.html

@@ -20,7 +20,9 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>Pull request #4: Creating and removing temporary tables was getting
+<ul><li>Foreign key: don't add a single column index if column 
+    is leading key of existing index.
+</li><li>Pull request #4: Creating and removing temporary tables was getting
     slower and slower over time, because an internal object id was allocated but
     never de-allocated.
 </li><li>Issue 609: the spatial index did not support NULL with update and delete operations.

h2/src/main/org/h2/command/ddl/AlterTableAddConstraint.java

@@ -199,15 +199,7 @@ public class AlterTableAddConstraint extends SchemaCommand {
                 isOwner = true;
                 index.getIndexType().setBelongsToConstraint(true);
             } else {
-                if (db.isStarting()) {
-                    // before version 1.3.176, an existing index was used:
-                    // must do the same to avoid
-                    // Unique index or primary key violation:
-                    // "PRIMARY KEY ON """".PAGE_INDEX"
-                    index = getIndex(table, indexColumns, true);
-                } else {
-                    index = getIndex(table, indexColumns, false);
-                }
+                index = getIndex(table, indexColumns, true);
                 if (index == null) {
                     index = createIndex(table, indexColumns, false);
                     isOwner = true;

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

@@ -145,6 +145,16 @@ public class TestCases extends TestBase {
                 "foreign key(a_id) references a(id)");
         stat.execute("update a set x=200");
         stat.execute("drop table if exists a, b");
+
+        stat.execute("drop all objects");
+        stat.execute("create table parent(id int primary key)");
+        stat.execute("create table child(id int, parent_id int, x int)");
+        stat.execute("create index y on child(parent_id, x)");
+        stat.execute("alter table child add constraint z foreign key(parent_id) references parent(id)");
+        ResultSet rs = stat.executeQuery("select * from information_schema.indexes where table_name = 'CHILD'");
+        while (rs.next()) {
+            assertEquals("Y", rs.getString("index_name"));
+        }
         conn.close();
     }