code: public String getKey(String tableName, String query, Object[] params) {
          return tableName + query + (params == null ? null : Arrays.asList(params).toString());
      }
docs: Generates a cache key. Subclasses may override this implementation.
  
  @param tableName name of a table
  @param query query
  @param params query parameters.
  @return generated key for tied to these parameters.