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From Edmond Lau <>
Subject Re: Would deleted columns slow down reads?
Date Fri, 26 Feb 2010 07:56:25 GMT
Thanks for the confirmation - that's what I suspected.


On Thu, Feb 25, 2010 at 7:00 PM, Jonathan Ellis <> wrote:
> Yes, that's going to hurt forward scans with no start column.
> (Reverse scans, or scans that start with a known live column, will
> still be fast b/c of the per-row column indexes.)
> On Thu, Feb 25, 2010 at 8:56 PM, Edmond Lau <> wrote:
>> Given that Cassandra needs to maintain tombstones to handle
>> distributed deletes, does the existence of deleted columns slow down
>> slices?
>> To be more concrete, suppose I used a row as a queue.  I keep adding
>> columns to the end of the sort order of a column family, and I keep
>> deleting columns from the start of the sort order.  After some time,
>> the row would have a large number of deleted columns followed by a
>> number of undeleted columns in the column family.  Does slicing for
>> the first N columns from the row now require scanning over all the
>> initial deleted columns (meaning reads would get more expensive as
>> time goes on), or are the deleted columns stored separately to enable
>> Cassandra to skip over deleted columns when processing reads?
>> Edmond

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