Deleted Items

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  Rahul_Choudhary

  June 2016

  Hi

   

  The DELETE statement does not actually delete data from the disk storage; it marks rows as deleted so that they can be retrieved by historical queries.

  The DELETE statement does not delete the data from the disk storage. Instead, the statement creates a delete vector that records the position of the deleted record and the epoch when the delete was committed.
  
  There is no such specific table for such items but you can always check dc_requests_issued,query_requests to check for the queries that you have run to identify such delete statements from there.

   

   

  Also to make the disk space reusable, Vertica allows you to permanently remove the deleted data from the physical storage of the database. The deleted data is permanently removed from the ROS container. You can control the deletion of data in the physical storage of your database by enabling the Tuple Mover to remove the data automatically or removing the data manually.

   

  The Ancient History Mark (AHM) decides when the data is removed permanently. The AHM is an epoch that represents the time until which the history is retained.

   

  You can check delete_vectors table specifically to check for different projections having the delete vector count.

   

  It's a wide topic and I would  suggest you to read the vertica documentation for more information on this.

   

  Thanks

  Rahul

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