https://stackoverflow.com/questions/6698207/delete-all-vs-destroy-all

• destroy_all: call destroy method of all matched objects. i.e. one SQL for one object

• delete_all: one SQL delete for all matched results.

  • NOTE：It seems to be update if use reference e.g.

       table.datetime_cells.delete_all 
        DatetimeCell Update All (0.3ms)  UPDATE "datetime_cells" SET "table_id" = $1 WHERE "datetime_cells"."table_id" = $2  [["table_id", nil], ["table_id", 7]]
       datetime_cells.where(table:talbe).delete_all # OK