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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Would deleted columns slow down reads?
Date Fri, 26 Feb 2010 03:00:34 GMT
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 <edmond@ooyala.com> 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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