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From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-2589) row deletes do not remove columns
Date Fri, 17 Jun 2011 06:12:47 GMT


Jonathan Ellis commented on CASSANDRA-2589:

bq. I'm passing Integer.MIN_VALUE for the gcBefore so I thought it would only remove colums
if they were under a CF tombstone. 

Ah, you're right.

bq. One of the issues I ran into is that while it's seems technically correct to purge a tombstone
after GCGraceSeconds, if it is not written into an SSTable it's lost. 

Not sure what you mean. Yes, it's lost, but why would we not want to lose a tombstone-older-than-GCGrace?

> row deletes do not remove columns
> ---------------------------------
>                 Key: CASSANDRA-2589
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Aaron Morton
>            Assignee: Aaron Morton
>            Priority: Minor
>             Fix For: 0.8.2
>         Attachments: 0001-remove-deleted-columns-before-flushing-memtable-v07.patch,
> When a row delete is issued CF.delete() sets the localDeletetionTime and markedForDeleteAt
values but does not remove columns which have a lower 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no longer valid.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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