Fix incorrect reads from the undo log

h2/src/main/org/h2/mvstore/db/TransactionStore.java

@@ -1286,7 +1286,12 @@ public class TransactionStore {
                     // transaction (possibly one with the same id)
                     data = map.get(key);
                 } else {
-                    data = (VersionedValue) d[2];
+                    if (map.getId() == (int) d[0]) {
+                        data = (VersionedValue) d[2];
+                    } else {
+                        // this entry does not belong to this map, try again
+                        data = map.get(key);
+                    }
                 }
             }
         }

h2/src/test/org/h2/test/mvcc/TestMvccMultiThreaded2.java

@@ -12,6 +12,7 @@ import java.sql.SQLException;
 import java.sql.Statement;
 import java.util.ArrayList;
 import org.h2.jdbc.JdbcSQLException;
+import org.h2.message.DbException;
 import org.h2.test.TestBase;
 import org.h2.util.IOUtils;
 
@@ -80,9 +81,11 @@ public class TestMvccMultiThreaded2 extends TestBase {
         @SuppressWarnings("unused")
         int minProcessed = Integer.MAX_VALUE, maxProcessed = 0, totalProcessed = 0;
 
+        boolean allOk = true;
         for (SelectForUpdate sfu : threads) {
             // make sure all threads have stopped by joining with them
             sfu.join();
+            allOk &= sfu.ok;
             totalProcessed += sfu.iterationsProcessed;
             if (sfu.iterationsProcessed > maxProcessed) {
                 maxProcessed = sfu.iterationsProcessed;
@@ -102,6 +105,8 @@ public class TestMvccMultiThreaded2 extends TestBase {
 
         IOUtils.closeSilently(conn);
         deleteDb(getTestName());
+
+        assertTrue(allOk);
     }
 
     /**
@@ -111,6 +116,8 @@ public class TestMvccMultiThreaded2 extends TestBase {
 
         public int iterationsProcessed;
 
+        public boolean ok;
+
         SelectForUpdate() {
         }
 
@@ -149,11 +156,13 @@ public class TestMvccMultiThreaded2 extends TestBase {
                 }
             } catch (SQLException e) {
                 TestBase.logError("SQL error from thread "+getName(), e);
+                throw DbException.convert(e);
             } catch (Exception e) {
                 TestBase.logError("General error from thread "+getName(), e);
                 throw e;
             }
             IOUtils.closeSilently(conn);
+            ok = true;
         }
     }
 }