Re: How to keep only exactly column of key

2011-07-20 Thread Sylvain Lebresne
ailto:sylv...@datastax.com] > Sent: Tuesday, July 19, 2011 11:40 AM > To: user@cassandra.apache.org > Subject: Re: How to keep only exactly column of key > > On Tue, Jul 19, 2011 at 10:15 AM, Lior Golan wrote: >> Can't this capping be done (approximately) during compaction. &g

RE: How to keep only exactly column of key

2011-07-20 Thread Lior Golan
@cassandra.apache.org Subject: Re: How to keep only exactly column of key On Tue, Jul 19, 2011 at 10:15 AM, Lior Golan wrote: > Can't this capping be done (approximately) during compaction. > Something > like: > > 1.   Ability to define for a column family that it's a &q

Re: How to keep only exactly column of key

2011-07-19 Thread Sylvain Lebresne
compaction that just drop columns after the N first. It would then be on the client side to deal with the possibility to get more that the first N ones, but as you said, if it is for automated cleanup, that will be enough. -- Sylvain > From: Tupshin Harper [mailto:tups...@tupshin.com] &g

RE: How to keep only exactly column of key

2011-07-19 Thread Lior Golan
cleanup, and not for enforcing exactly N columns, I think this would be sufficient From: Tupshin Harper [mailto:tups...@tupshin.com] Sent: Tuesday, July 19, 2011 10:04 AM To: user@cassandra.apache.org Subject: Re: How to keep only exactly column of key Speaking from practical experience, it is

Re: How to keep only exactly column of key

2011-07-19 Thread Tupshin Harper
Speaking from practical experience, it is possible to simulate this feature by retrieving a slice of your row that only contains the most recent 100 items. You can then prevent the rows from growing out of control by checking the size of the row and pruning it back to 100 every N writes, where N is

Re: How to keep only exactly column of key

2011-07-18 Thread Jonathan Ellis
You can use expiring columns to say "only the last N seconds' of data." But not counts per se for the reasons Aaron gave. On Mon, Jul 18, 2011 at 10:22 AM, JKnight JKnight wrote: > Dear all, > I want to keep only 100 column of a key: when I add a column for a key, if > the number column of key i

Re: How to keep only exactly column of key

2011-07-18 Thread Sameer Farooqui
The Datastax post on counters says: "Prior to 0.8, Cassandra had no simple and efficient way to count. By “counting,” we mean here to provide an atomic increment operation in a single column value, as opposed to counting the number of columns in a row, or rows in a column family, both of which were

Re: How to keep only exactly column of key

2011-07-18 Thread aaron morton
There is no support for a feature like that, and i doubt it would ever be supported. For one there there are no locks during a write, so it's not possible to definitively say there are 100 columns at a particular instance of time. You would need to read all columns and delete the ones you no l