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From Sylvain Lebresne <sylv...@datastax.com>
Subject Re: Frequent updates of freshly written columns
Date Fri, 18 Feb 2011 08:36:13 GMT
On Fri, Feb 18, 2011 at 8:14 AM, Aklin_81 <asdkl93@gmail.com> wrote:

> Are the very freshly written columns to a row in memtables, efficiently
> updated/overwritten by edited/new column values.
>
> After flushing of memtable, are those(edited + unedited ones) columns
> stored together on disk (in same blocks!?) as if they were written in one
> single operation or same time ?? I know if old columns are edited then
> several copies of same column will be dispersed in different sst tables,
> what about fresh columns ?
>
> Are there any disadvantages to frequently updating fresh columns present in
> memtable ?
>

The SSTables are immutable but the memtable are not. As long as you
update/overwrite a column that is still in memtable, it is simply replaced
in memory (so it's as efficient as it gets).
In other words, when the memtable is flushed, only the last version of the
column goes in.

--
Sylvain

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