MVCC: concurrently updating a row could result in the row to appear deleted in…

MVCC: concurrently updating a row could result in the row to appear deleted in the second connection, if there are multiple unique indexes (or a primary key and at least one unique index). Thanks a lot to Teruo for the patch!

h2/src/main/org/h2/table/Table.java

@@ -419,6 +419,8 @@ public abstract class Table extends SchemaObjectBase {
      *            new row,...
      */
     public void updateRows(Prepared prepared, Session session, RowList rows) {
+        // in case we need to undo the update
+        int rollback = session.getUndoLogPos();
         // remove the old rows
         int rowScanCount = 0;
         for (rows.reset(); rows.hasNext();) {
@@ -437,7 +439,14 @@ public abstract class Table extends SchemaObjectBase {
             }
             rows.next();
             Row n = rows.next();
-            addRow(session, n);
+            try {
+                addRow(session, n);
+            } catch (DbException e) {
+                if (e.getErrorCode() == ErrorCode.CONCURRENT_UPDATE_1) {
+                    session.rollbackTo(rollback, false);
+                }
+                throw e;
+            }
             session.log(this, UndoLogRecord.INSERT, n);
         }
     }

h2/src/test/org/h2/test/mvcc/TestMvcc3.java

@@ -24,10 +24,13 @@ public class TestMvcc3 extends TestBase {
      * @param a ignored
      */
     public static void main(String... a) throws Exception {
-        TestBase.createCaller().init().test();
+        TestBase test = TestBase.createCaller().init();
+        test.config.mvcc = true;
+        test.test();
     }
 
     public void test() throws SQLException {
+        testConcurrentUpdate();
         testInsertUpdateRollback();
         testCreateTableAsSelect();
         testSequence();
@@ -36,6 +39,50 @@ public class TestMvcc3 extends TestBase {
         deleteDb("mvcc3");
     }
 
+    private void testConcurrentUpdate() throws SQLException {
+        if (!config.mvcc) {
+            return;
+        }
+        deleteDb("mvcc3");
+        Connection c1 = getConnection("mvcc3");
+        c1.setAutoCommit(false);
+        Statement s1 = c1.createStatement();
+        Connection c2 = getConnection("mvcc3");
+        c2.setAutoCommit(false);
+        Statement s2 = c2.createStatement();
+
+        s1.execute("create table test(id int primary key, name varchar) as select x, x from system_range(1, 2)");
+        s1.execute("create unique index on test(name)");
+        s1.executeUpdate("update test set name = 100 where id = 1");
+
+        try {
+            s2.executeUpdate("update test set name = 100 where id = 2");
+            fail();
+        } catch (SQLException e) {
+            // expected
+        }
+
+
+        ResultSet rs = s1.executeQuery("select * from test order by id");
+        assertTrue(rs.next());
+        assertEquals(1, rs.getInt(1));
+        assertEquals("100", rs.getString(2));
+        assertTrue(rs.next());
+        assertEquals(2, rs.getInt(1));
+        assertEquals("2", rs.getString(2));
+        assertFalse(rs.next());
+        rs = s2.executeQuery("select * from test order by id");
+        assertTrue(rs.next());
+        assertEquals(1, rs.getInt(1));
+        assertEquals("1", rs.getString(2));
+        assertTrue(rs.next());
+        assertEquals(2, rs.getInt(1));
+        assertEquals("2", rs.getString(2));
+        assertFalse(rs.next());
+        c1.close();
+        c2.close();
+    }
+
     private void testInsertUpdateRollback() throws SQLException {
         if (!config.mvcc) {
             return;
@@ -188,6 +235,7 @@ public class TestMvcc3 extends TestBase {
         assertEquals(1, rs.getInt(1));
         conn.close();
     }
+
 }