I have a requirement to delete records from a Postgres SQL table which has more than 200 million records. The table is not having any primary key.

The sample table (Bookmark is the name of table) content is as below:

Code:
    systemId	 filename		    mindatetime					maxdatetime
      70277		monitor_1.dat	2019-04-21 08:00:00 AM		2019-04-21 03:10:00 PM
      10006		monitor_2.dat	2019-04-25 10:00:00 AM		2019-04-25
...