row deletes do not remove columns
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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they are no longer valid.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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