Fix for issue #1298

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

@@ -149,16 +149,9 @@ public class TransactionStore {
         if (!init) {
             for (String mapName : store.getMapNames()) {
                 if (mapName.startsWith(UNDO_LOG_NAME_PREFIX)) {
-                    // The following block will be executed only once
-                    // upon upgrade from older version where
-                    // undo log was persisted as a single map
-                    if (mapName.equals(UNDO_LOG_NAME_PREFIX)) {
-                        if (!store.hasData(mapName) && !store.isReadOnly()) {
-                            store.removeMap(mapName);
-                        }
-                        continue;
-                    }
-
+                    // Unexpectedly short name may be encountered upon upgrade from older version
+                    // where undo log was persisted as a single map, remove it.
+                    if (mapName.length() > UNDO_LOG_NAME_PREFIX.length()) {
                         boolean committed = mapName.charAt(UNDO_LOG_NAME_PREFIX.length()) == UNDO_LOG_COMMITTED;
                         if (store.hasData(mapName) || committed) {
                             int transactionId = Integer.parseInt(mapName.substring(UNDO_LOG_NAME_PREFIX.length() + 1));
@@ -185,7 +178,13 @@ public class TransactionStore {
                                 long logId = lastUndoKey == null ? 0 : getLogId(lastUndoKey) + 1;
                                 registerTransaction(transactionId, status, name, logId, timeoutMillis, 0,
                                         RollbackListener.NONE);
+                                continue;
+                            }
+                        }
                     }
+
+                    if (!store.hasData(mapName) && !store.isReadOnly()) {
+                        store.removeMap(mapName);
                     }
                 }
             }