#fixed code
                              @Override
  public Status read(String table, String key, Set<String> fields,
      Map<String, ByteIterator> result) {
    try {
      PreparedStatement stmt = (fields == null) ? readAllStmt.get() : readStmts.get(fields);

      // Prepare statement on demand
      if (stmt == null) {
        Select.Builder selectBuilder;

        if (fields == null) {
          selectBuilder = QueryBuilder.select().all();
        } else {
          selectBuilder = QueryBuilder.select();
          for (String col : fields) {
            ((Select.Selection) selectBuilder).column(col);
          }
        }

        stmt = session.prepare(selectBuilder.from(table)
                               .where(QueryBuilder.eq(YCSB_KEY, QueryBuilder.bindMarker()))
                               .limit(1));
        stmt.setConsistencyLevel(readConsistencyLevel);
        if (trace) {
          stmt.enableTracing();
        }

        PreparedStatement prevStmt = (fields == null) ?
                                     readAllStmt.getAndSet(stmt) :
                                     readStmts.putIfAbsent(new HashSet(fields), stmt);
        if (prevStmt != null) {
          stmt = prevStmt;
        }
      }

      logger.debug(stmt.getQueryString());
      logger.debug("key = {}", key);

      ResultSet rs = session.execute(stmt.bind(key));

      if (rs.isExhausted()) {
        return Status.NOT_FOUND;
      }

      // Should be only 1 row
      Row row = rs.one();
      ColumnDefinitions cd = row.getColumnDefinitions();

      for (ColumnDefinitions.Definition def : cd) {
        ByteBuffer val = row.getBytesUnsafe(def.getName());
        if (val != null) {
          result.put(def.getName(), new ByteArrayByteIterator(val.array()));
        } else {
          result.put(def.getName(), null);
        }
      }

      return Status.OK;

    } catch (Exception e) {
      logger.error(MessageFormatter.format("Error reading key: {}", key).getMessage(), e);
      return Status.ERROR;
    }

  }
#vulnerable code 
                              @Override
  public Status read(String table, String key, Set<String> fields,
      Map<String, ByteIterator> result) {
    try {
      Statement stmt;
      Select.Builder selectBuilder;

      if (fields == null) {
        selectBuilder = QueryBuilder.select().all();
      } else {
        selectBuilder = QueryBuilder.select();
        for (String col : fields) {
          ((Select.Selection) selectBuilder).column(col);
        }
      }

      stmt = selectBuilder.from(table).where(QueryBuilder.eq(YCSB_KEY, key))
          .limit(1);
      stmt.setConsistencyLevel(readConsistencyLevel);

      if (debug) {
        System.out.println(stmt.toString());
      }
      if (trace) {
        stmt.enableTracing();
      }
      
      ResultSet rs = session.execute(stmt);

      if (rs.isExhausted()) {
        return Status.NOT_FOUND;
      }

      // Should be only 1 row
      Row row = rs.one();
      ColumnDefinitions cd = row.getColumnDefinitions();

      for (ColumnDefinitions.Definition def : cd) {
        ByteBuffer val = row.getBytesUnsafe(def.getName());
        if (val != null) {
          result.put(def.getName(), new ByteArrayByteIterator(val.array()));
        } else {
          result.put(def.getName(), null);
        }
      }

      return Status.OK;

    } catch (Exception e) {
      e.printStackTrace();
      System.out.println("Error reading key: " + key);
      return Status.ERROR;
    }

  } 
                            #location 21 
                            #vulnerability type THREAD_SAFETY_VIOLATION