Vertica system housekeeping re non deletes
Hi,
Given that Vertica doesn't delete data, it just marks it as deleted, what happens to it's internal 'system catalogue' when objects are created and dropped ... does this grow and grow until some housekeeping function is performed.
If so, how is this resolved ? I used to work with another MPP (Kognitio) which required a system bounce to clear down its system tables (whereas data tables needed to be moved between 'slabs').
Thanks again.
0
Comments
Hi,
Yes, vertica marks rows which are deleted and you can find the number of rows deleted for a particular projection from the v_monitor.delete_vectors system table. Internal Sytem catalogue grows in size and "Automatic Mergeout" is performed by Tuple Mover (HP Vertica database optimizer) to purge all delete records. A mergeout is a process of consolidating all ROS containers and purging deleted records.
To know more information about mergeout process, Please go through the followig link
https://my.vertica.com/docs/7.1.x/HTML/index.htm#Authoring/AdministratorsGuide/TupleMover/Mergeout.htm%3FTocPath%3DAdministrator's%2520Guide%7CManaging%2520the%2520Database%7CManaging%2520Tuple%2520Mover%2520Operations%7CUnderstanding%2520the%2520Tuple%2520Mover%7C_____2
-Regards,
Sruthi