One example could be to identify when a row was last updated. For example, if I have a column family for storing users, the row key is a user ID and the columns are values for that user, e.g. natural column names would be "firstName", "lastName", "address", etc; column names don't naturally include a date here.
Sorting the coulmns by timestamp and picking the last would allow me to know when the row was last modified. (I could manually maintain a 'last modified' column as well, I know, but just coming up with a use case :). /Martin Koch On Fri, Oct 12, 2012 at 11:39 PM, B. Todd Burruss <bto...@gmail.com> wrote: > trying to think of a use case where you would want to order by > timestamp, and also have unique column names for direct access. > > not really trying to challenge the use case, but you can get ordering > by timestamp and still maintain a "name" for the column using > composites. if the first component of the composite is a timestamp, > then you can order on it. when retrieved you will could have a "name" > in the second component .. and have dupes as long as the timestamp is > unique (use TimeUUID) > > > On Fri, Oct 12, 2012 at 7:20 AM, Derek Williams <de...@fyrie.net> wrote: > > You probably already know this but I'm pretty sure it wouldn't be a > trivial > > change, since to efficiently lookup a column by name requires the > columns to > > be ordered by name. A separate index would be needed in order to provide > > lookup by column name if the row was sorted by timestamp (which is the > way > > Redis implements it's sorted set). > > > > > > On Fri, Oct 12, 2012 at 12:13 AM, Ertio Lew <ertio...@gmail.com> wrote: > >> > >> "Make column timestamps optional"- kidding me, right ?:) I do > understand > >> that this wont be possible as then cassandra wont be able to > distinguish the > >> latest among several copies of same column. I dont mean that. I just > want > >> the while ordering the columns, Cassandra(in an optional mode per CF) > should > >> not look at column names(they will exist though but for retrieval > purposes > >> not for ordering) but instead Cassandra would order the columns by > looking > >> at the timestamp values(timestamps would exist!). So the change would be > >> just to provide a mode in which cassandra, while ordering, uses > timestamps > >> instead of column names. > >> > >> > >> On Fri, Oct 12, 2012 at 2:26 AM, Tyler Hobbs <ty...@datastax.com> > wrote: > >>> > >>> Without thinking too deeply about it, this is basically equivalent to > >>> disabling timestamps for a column family and using timestamps for > column > >>> names, though in a very indirect (and potentially confusing) manner. > So, if > >>> you want to open a ticket, I would suggest framing it as "make column > >>> timestamps optional". > >>> > >>> > >>> On Wed, Oct 10, 2012 at 4:44 AM, Ertio Lew <ertio...@gmail.com> wrote: > >>>> > >>>> I think Cassandra should provide an configurable option on per column > >>>> family basis to do columns sorting by time-stamp rather than column > names. > >>>> This would be really helpful to maintain time-sorted columns without > using > >>>> up the column name as time-stamps which might otherwise be used to > store > >>>> most relevant column names useful for retrievals. Very frequently we > need to > >>>> store data sorted in time order. Therefore I think this may be a very > >>>> general requirement & not specific to just my use-case alone. > >>>> > >>>> Does it makes sense to create an issue for this ? > >>>> > >>>> > >>>> > >>>> > >>>> On Fri, Mar 25, 2011 at 2:38 AM, aaron morton < > aa...@thelastpickle.com> > >>>> wrote: > >>>>> > >>>>> If you mean order by the column timestamp (as passed by the client) > >>>>> that it not possible. > >>>>> > >>>>> Can you use your own timestamps as the column name and store them as > >>>>> long values ? > >>>>> > >>>>> Aaron > >>>>> > >>>>> On 25 Mar 2011, at 09:30, Narendra Sharma wrote: > >>>>> > >>>>> > Cassandra 0.7.4 > >>>>> > Column names in my CF are of type byte[] but I want to order > columns > >>>>> > by timestamp. What is the best way to achieve this? Does it make > sense for > >>>>> > Cassandra to support ordering of columns by timestamp as option > for a column > >>>>> > family irrespective of the column name type? > >>>>> > > >>>>> > Thanks, > >>>>> > Naren > >>>>> > >>>> > >>> > >>> > >>> > >>> -- > >>> Tyler Hobbs > >>> DataStax > >>> > >> > > > > > > > > -- > > Derek Williams > > >
