+    private int updateFolderSize(SQLiteDatabase db, String folderId) {
+        int count = 0;
+        String [] whereArgs = new String[] { folderId };
+        
+        // read current size saved for the folder 
+        long folderSize = 0;
+        long folderParentId = -1;
+        Uri selectFolderUri = Uri.withAppendedPath(ProviderTableMeta.CONTENT_URI_FILE, folderId);
+        String[] folderProjection = new String[] { ProviderTableMeta.FILE_CONTENT_LENGTH,  ProviderTableMeta.FILE_PARENT};
+        String folderWhere = ProviderTableMeta._ID + "=?";
+        Cursor folderCursor = query(db, selectFolderUri, folderProjection, folderWhere, whereArgs, null);
+        if (folderCursor != null && folderCursor.moveToFirst()) {
+            folderSize = folderCursor.getLong(folderCursor.getColumnIndex(ProviderTableMeta.FILE_CONTENT_LENGTH));;
+            folderParentId = folderCursor.getLong(folderCursor.getColumnIndex(ProviderTableMeta.FILE_PARENT));;
+        }
+        folderCursor.close();
+        
+        // read and sum sizes of children
+        long childrenSize = 0;
+        Uri selectChildrenUri = Uri.withAppendedPath(ProviderTableMeta.CONTENT_URI_DIR, folderId);
+        String[] childrenProjection = new String[] { ProviderTableMeta.FILE_CONTENT_LENGTH,  ProviderTableMeta.FILE_PARENT};
+        String childrenWhere = ProviderTableMeta.FILE_PARENT + "=?";
+        Cursor childrenCursor = query(db, selectChildrenUri, childrenProjection, childrenWhere, whereArgs, null);
+        if (childrenCursor != null && childrenCursor.moveToFirst()) {
+            while (!childrenCursor.isAfterLast()) {
+                childrenSize += childrenCursor.getLong(childrenCursor.getColumnIndex(ProviderTableMeta.FILE_CONTENT_LENGTH));
+                childrenCursor.moveToNext();
+            }
+        }
+        childrenCursor.close();
+        
+        // update if needed
+        if (folderSize != childrenSize) {
+            Log_OC.d("FileContentProvider", "Updating " + folderSize + " to " + childrenSize);
+            ContentValues cv = new ContentValues();
+            cv.put(ProviderTableMeta.FILE_CONTENT_LENGTH, childrenSize);
+            count = db.update(ProviderTableMeta.DB_NAME, cv, folderWhere, whereArgs);
+            
+            // propagate update until root
+            if (folderParentId > FileDataStorageManager.ROOT_PARENT_ID) {
+                Log_OC.d("FileContentProvider", "Propagating update to " + folderParentId);
+                updateFolderSize(db, String.valueOf(folderParentId));
+            } else {
+                Log_OC.d("FileContentProvider", "NOT propagating to " + folderParentId);
+            }
+        } else {
+            Log_OC.d("FileContentProvider", "NOT updating, sizes are " + folderSize + " and " + childrenSize);
+        }
+        return count;
+    }
+
+