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From Apache Wiki <wikidi...@apache.org>
Subject FAQ reverted to revision 69 on Cassandra Wiki
Date Fri, 11 Jun 2010 20:59:21 GMT
Dear wiki user,

You have subscribed to a wiki page "Cassandra Wiki" for change notification.

The page FAQ has been reverted to revision 69 by JonathanEllis.
The comment on this change is: range ghosts is just the href anchor.
http://wiki.apache.org/cassandra/FAQ?action=diff&rev1=70&rev2=71

--------------------------------------------------

  == Why do deleted keys show up during range scans? ==
  Because get_range_slice says, "apply this predicate to the range of rows given," meaning,
if the predicate result is empty, we have to include an empty result for that row key.  It
is perfectly valid to perform such a query returning empty column lists for some or all keys,
even if no deletions have been performed.
  
- So to special case leaving out result entries for deletions, we would have to check the
entire rest of the row to make sure there is no undeleted data anywhere else either (in which
case leaving the key out would be an error). These rows are also called "range ghosts".
+ So to special case leaving out result entries for deletions, we would have to check the
entire rest of the row to make sure there is no undeleted data anywhere else either (in which
case leaving the key out would be an error).
  
  This is what we used to do with the old get_key_range method, but the performance hit turned
out to be unacceptable.
  

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