Revert "MISC - use attr_reader i/o class_attribute for columns_pool"
Revert "MISC - use attr_reader i/o class_attribute for columns_pool"

This reverts commit ead8c75abbfc1cd6adb66dee63d21e1ed66f8cd6.

ekohe/wulin_master,ekohe/wulin_master,ekohe/wulin_master