hi, the time-to-live feature in 0.7 is very nice and it made me want to ask about a somewhat similar feature.
i have a stream of data consisting of entities and associated samples. so i create a row for each entity and the columns in each row contain the samples for that entity. when i get around to processing an entity i only care about the most recent N samples. so i read the most recent N columns and delete all the rest. what i would like would be a column family property that allows me to specify a maximum number of columns per row. then i could just keep writing and not have to do the deletes. in my case it would be fine if the limit is only 'eventually' applied (so that sometimes there might be extra columns). does this seem like a generally useful feature? if so, would it be hard to implement (maybe it could be done at compaction time like the TTL feature)? thanks, -mike
