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From "Gary Helmling (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-11292) Add an "undelete" operation
Date Tue, 03 Jun 2014 17:24:01 GMT
Gary Helmling created HBASE-11292:
-------------------------------------

             Summary: Add an "undelete" operation
                 Key: HBASE-11292
                 URL: https://issues.apache.org/jira/browse/HBASE-11292
             Project: HBase
          Issue Type: New Feature
          Components: Deletes
            Reporter: Gary Helmling


While column families can be configured to keep deleted cells (allowing time range queries
to still retrieve those cells), deletes are still somewhat unique in that they are irreversible
operations.  Once a delete has been issued on a cell, the only way to "undelete" it is to
rewrite the data with a timestamp newer than the delete.

The idea here is to add an "undelete" operation, that would make it possible to cancel a previous
delete.  An undelete operation will be similar to a delete, in that it will be written as
a marker ("tombstone" doesn't seem like the right word).  The undelete marker, however, will
sort prior to a delete marker, canceling the effect of any following delete.

In the absence of a column family configured to KEEP_DELETED_CELLS, we can't be sure if a
prior delete marker and the effected cells have already been garbage collected.  In this case
(column family not configured with KEEP_DELETED_CELLS) it may be necessary for the server
to reject undelete operations to avoid creating the appearance of a client contact for undeletes
that can't reliably be honored.

I think there are additional subtleties of the implementation to be worked out, but I'm also
interested in a broader discussion of interest in this capability.



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