OK I will try to separate them out. On Sat, Mar 13, 2010 at 5:35 AM, Jonathan Ellis <jbel...@gmail.com> wrote:
> You should submit your minor change to jira for others who might want to > try it. > > On Sat, Mar 13, 2010 at 3:18 AM, Weijun Li <weiju...@gmail.com> wrote: > > Tried Sylvain's feature in 0.6 beta2 (need minor change) and it worked > > perfectly. Without this feature, as far as you have high volume new and > > expired columns your life will be miserable :-) > > > > Thanks for great job Sylvain!! > > > > -Weijun > > > > On Fri, Mar 12, 2010 at 12:27 AM, Sylvain Lebresne <sylv...@yakaz.com> > > wrote: > >> > >> I guess you can also vote for this ticket : > >> https://issues.apache.org/jira/browse/CASSANDRA-699 :) > >> > >> </advertising> > >> > >> -- > >> Sylvain > >> > >> > >> On Fri, Mar 12, 2010 at 8:28 AM, Mark Robson <mar...@gmail.com> wrote: > >> > On 12 March 2010 03:34, Bill Au <bill.w...@gmail.com> wrote: > >> >> > >> >> Let take Twitter as an example. All the tweets are timestamped. I > >> >> want > >> >> to keep only a month's worth of tweets for each user. The number of > >> >> tweets > >> >> that fit within this one month window varies from user to user. What > >> >> is the > >> >> best way to accomplish this? > >> > > >> > This is the "expiry" problem that has been discussed on this list > >> > before. As > >> > far as I can see there are no easy ways to do it with 0.5 > >> > > >> > If you use the ordered partitioner and make the first part of the keys > a > >> > timestamp (or part of it) then you can get the keys and delete them. > >> > > >> > However, these deletes will be quite inefficient, currently each row > >> > must be > >> > deleted individually (there was a patch to range delete kicking > around, > >> > I > >> > don't know if it's accepted yet) > >> > > >> > But even if range delete is implemented, it's still quite inefficient > >> > and > >> > not really what you want, and doesn't work with the RandomPartitioner > >> > > >> > If you have some metadata to say who tweeted within a given period > (say > >> > 10 > >> > days or 30 days) and you store the tweets all in the same key per user > >> > per > >> > period (say with one column per tweet, or use supercolumns), then you > >> > can > >> > just delete one key per user per period. > >> > > >> > One of the problems with using a time-based key with ordered > partitioner > >> > is > >> > that you're always going to have a data imbalance, so you may want to > >> > try > >> > hashing *part* of the key (The first part) so you can still range scan > >> > the > >> > next part. This may fix load balancing while still enabling you to use > >> > range > >> > scans to do data expiry. > >> > > >> > e.g. your key is > >> > > >> > Hash of day number + user id + timestamp > >> > > >> > Then you can range scan the entire day's tweets to expire them, and > >> > range > >> > scan a given user's tweets for a given day efficiently (and doing this > >> > for > >> > 30 days is just 30 range scans) > >> > > >> > Putting a hash in there fixes load balancing with OPP. > >> > > >> > Mark > >> > > > > > >
