Postgres uses a mechanism called MVCC(Multi Version Concurrency Control) to track changes in your database. Due to this reason, some of the rows become “dead”. Dead rows are generated by DELETE and UPDATE operations, as well as transactions that have to be rolled back. Refer this link learn more about MVCC. These dead rows keep on adding as there are lots of updates and deletes. Periodic clean up of these dead rows is necessary to not only save space but also maintain the performance of your database queries. The space taken by these dead rows is called bloat. You