I've used "special" values which still comply with the Composite schema for the metadata columns, e.g. a column of 1970-01-01:{accountId} for a metadata column where the Composite is DateType:UTF8Type.
Jim On Sat, Feb 4, 2012 at 2:13 PM, Yiming Sun <yiming....@gmail.com> wrote: > 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 > >