I also made something like this a while ago. I decided to go for the 2-rows-solution: by doing that you don't have the need for super columns. Cassandra is really good at reading, so this should not be an issue.
Cheers! 2012/2/4 Yiming Sun <yiming....@gmail.com> > Thanks Andrey and Chris. It sounds like we don't necessarily have to use > composite columns. From what I understand about dynamic CF, each row may > have completely different data from other rows; but in our case, the data > in each row is similar to other rows; my concern was more about the > homogeneity of the data between columns. > > In our original supercolumn-based schema, one special supercolumn is > called "metadata" which contains a number of subcolumns to hold metadata > describing each collection (e.g. number of documents, etc.), then the rest > of the supercolumns in the same row are all IDs of documents belong to the > collection, and for each document supercolumn, the subcolumns contain the > document content as well as metadata on individual document (e.g. checksum > of each document). > > To move away from the supercolumn schema, I could either create two CFs, > one to hold metadata, the other document content; or I could create just > one CF mixing metadata and doc content in the same row, and using composite > column names to identify if the particular column is metadata or a > document. I am just wondering if you have any inputs on the pros and cons > of each schema. > > -- Y. > > > On Fri, Feb 3, 2012 at 10:27 PM, Chris Gerken > <chrisger...@mindspring.com>wrote: > >> >> >> >> On 4 February 2012 06:21, Yiming Sun <yiming....@gmail.com> wrote: >> >>> I cannot have one composite column name with 3 components while another >>> with 4 components? >> >> Just put 4 components and left last empty (if it is same type)?! >> >> Another question I have is how flexible composite columns actually are. >>> If my data model has a CF containing US zip codes with the following >>> composite columns: >>> >>> {OH:Spring Field} : 45503 >>> {OH:Columbus} : 43085 >>> {FL:Spring Field} : 32401 >>> {FL:Key West} : 33040 >>> >>> I know I can ask cassandra to "give me the zip codes of all cities in >>> OH". But can I ask it to "give me the zip codes of all cities named Spring >>> Field" using this model? Thanks. >>> >> No. You set first composite component at first. >> >> >> I'd use a dynamic CF: >> row key = state abbreviation >> column name = city name >> column value = zip code (or a complex object, one of whose properties is >> zip code) >> >> you can iterate over the columns in a single row to get a state's city >> names and their zip code and you can do a get_range_slices on all keys for >> the columns starting and ending on the city name to find out the zip codes >> for a cities with the given name. >> >> I think >> >> - Chris >> > >