Issue 558: with the MVStore, a NullPointerException could occur when using LOBs…

Issue 558: with the MVStore, a NullPointerException could occur when using LOBs at session commit (LobStorageMap.removeLob).

h2/src/main/org/h2/store/LobStorageMap.java

@@ -273,6 +273,10 @@ public class LobStorageMap implements LobStorageInterface {
             trace("remove " + tableId + "/" + lobId);
         }
         Object[] value = lobMap.remove(lobId);
+        if (value == null) {
+            // already removed
+            return;
+        }
         byte[] streamStoreId = (byte[]) value[0];
         Object[] key = new Object[] {streamStoreId, lobId };
         refMap.remove(key);

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

@@ -61,6 +61,7 @@ public class TestLob extends TestBase {
 
     @Override
     public void test() throws Exception {
+        testCloseLobTwice();
         testCleaningUpLobsOnRollback();
         testClobWithRandomUnicodeChars();
         testCommitOnExclusiveConnection();
@@ -111,6 +112,20 @@ public class TestLob extends TestBase {
         deleteDb("lob");
         FileUtils.deleteRecursive(TEMP_DIR, true);
     }
+    
+    private void testCloseLobTwice() throws SQLException {
+        deleteDb("lob");
+        Connection conn = getConnection("lob");
+        PreparedStatement prep = conn.prepareStatement("set @c = ?");
+        prep.setCharacterStream(1, new StringReader(
+                new String(new char[10000])), 10000);
+        prep.execute();
+        prep.setCharacterStream(1, new StringReader(
+                new String(new char[10001])), 10001);
+        prep.execute();
+        conn.setAutoCommit(true);
+        conn.close();
+    }
 
     private void testCleaningUpLobsOnRollback() throws Exception {
         if (config.mvStore) {