Why is the history database of RHEV-M growing excessively?

Issue

• Why is the ovirt_engine_history RHEV database growing excessively?

postgres=# \l+
                                 List of databases
         Name         |     Owner      |...|  Size   | Tablespace |        Description
----------------------+----------------+...+---------+------------+--------------------------
 engine               | engine         |...| 825 MB  | pg_default |
 ovirt_engine_history | engine_history |...| 53 GB   | pg_default |
 postgres             | postgres       |...| 5590 kB | pg_default |
 rhevmreports         | engine_reports |...| 26 MB   | pg_default |
 template0            | postgres       |...| 5504 kB | pg_default |
 template1            | postgres       |...| 5512 kB | pg_default | default template database
(6 rows)

postgres=# \c ovirt_engine_history
psql (8.4.20)
You are now connected to database "ovirt_engine_history".

ovirt_engine_history=# SELECT relname as "Table",pg_size_pretty(pg_total_relation_size(relid)) As "Size", pg_size_pretty(pg_total_relation_size(relid) - pg_relation_size(relid)) as "External Size" FROM pg_catalog.pg_statio_user_tables ORDER BY pg_total_relation_size(relid) DESC;
               Table               |  Size   | External Size
-----------------------------------+---------+---------------
 vm_disk_samples_history           | 21 GB   | 10 GB
 vm_interface_samples_history      | 15 GB   | 10047 MB
 vm_disks_usage_samples_history    | 7671 MB | 490 MB
 vm_disks_usage_hourly_history     | 3211 MB | 156 MB
 host_interface_samples_history    | 1726 MB | 1395 MB
 vm_samples_history                | 1322 MB | 786 MB
[...]