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From "Aaron Morton (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-2589) row deletes do not remove columns
Date Mon, 02 May 2011 03:32:03 GMT
row deletes do not remove columns
---------------------------------

                 Key: CASSANDRA-2589
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2589
             Project: Cassandra
          Issue Type: Bug
          Components: Core
    Affects Versions: 0.8 beta 1, 0.7.5
            Reporter: Aaron Morton
            Assignee: Aaron Morton
            Priority: Minor


When a row delete is issued CF.delete() sets the localDeletetionTime and markedForDeleteAt
values but does not remove columns which have a higher time stamp. As a result:

# Memory which could be freed is held on to (prob not too bad as it's already counted)
# The deleted columns are serialised to disk, along with the CF info to say they are no longer
valid. 
# NamesQueryFilter and SliceQueryFilter have to do more work as they filter out the irrelevant
columns using QueryFilter.isRelevant()
# Also columns written with a lower time stamp after the deletion are added to the CF without
checking markedForDeletionAt.


This can cause RR to fail, will create another ticket for that and link. This ticket is for
a fix to removing the columns. 

Two options I could think of:

# Check for deletion when serialising to SSTable and ignore columns if the have a lower timestamp.
Otherwise leave as is so dead columns stay in memory. 
# Ensure at all times if the CF is deleted all columns it contains have a higher timestamp.

## I *think* this would include all column types (DeletedColumn as well) as the CF deletion
has the same effect. But not sure.
## Deleting (potentially) all columns in delete() will take time. Could track the highest
timestamp in the CF so the normal case of deleting all cols does not need to iterate. 
 




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