Is it true that you can also just get the same results as when you pick a UTF8 key with this content: keyA:keyB
Of should you really use the composite keys? If so, what is the big advantage of composite over combined utf-8 keys? Robin 2011/12/21 Sylvain Lebresne <sylv...@datastax.com> > On Tue, Dec 20, 2011 at 9:33 PM, Maxim Potekhin <potek...@bnl.gov> wrote: > > Thank you Aaron! As long as I have plain strings, would you say that I > would > > do almost as well with catenation? > > Not without a concatenation aware comparator. The padding aaron is talking > of > is not a mixed type problem only. What I mean here is that if you use a > simple > string comparator (UTF8Type, AsciiType or even BytesType), then you will > have > the following sorting: > "foo24:bar" > "foo:bar" > "foobar:bar" > because ':' is between '2' and 'b' in ascii, you could use another > separator but > you get the point. In other words, concatenating strings doesn't make the > comparator aware of that fact. > CompositeType on the other hand sorts each component separately, so it will > sort: > "foo" : "bar" > "foo24" : "bar" > "foobar" : "bar" > which is usually what you want. > > -- > Sylvain > > > > > Of course I realize that mixed types are a very different case where the > > composite is very useful. > > > > Thanks > > > > Maxim > > > > > > > > On 12/20/2011 2:44 PM, aaron morton wrote: > > > > Component values are compared in a type aware fashion, an Integer is an > > Integer. Not a 10 character zero padded string. > > > > You can also slice on the components. Just like with string concat, but > > nicer. . e.g. If you app is storing comments for a thing, and the column > > names have the form <comment_id, field> or <Integer, String> you can > slice > > for all properties of a comment or all properties for comments between > two > > comment_id's > > > > Finally, the client library knows what's going on. > > > > Hope that helps. > > > > ----------------- > > Aaron Morton > > Freelance Developer > > @aaronmorton > > http://www.thelastpickle.com > > > > On 21/12/2011, at 7:43 AM, Maxim Potekhin wrote: > > > > With regards to static, what are major benefits as it compares with > > string catenation (with some convenient separator inserted)? > > > > Thanks > > > > Maxim > > > > > > On 12/20/2011 1:39 PM, Richard Low wrote: > > > > On Tue, Dec 20, 2011 at 5:28 PM, Ertio Lew<ertio...@gmail.com> wrote: > > > > With regard to the composite columns stuff in Cassandra, I have the > > > > following doubts : > > > > > > 1. What is the storage overhead of the composite type column > names/values, > > > > The values are the same. For each dimension, there is 3 bytes overhead. > > > > > > 2. what exactly is the difference between the DynamicComposite and Static > > > > Composite ? > > > > Static composite type has the types of each dimension specified in the > > > > column family definition, so all names within that column family have > > > > the same type. Dynamic composite type lets you specify the type for > > > > each column, so they can be different. There is extra storage > > > > overhead for this and care must be taken to ensure all column names > > > > remain comparable. > > > > > > > > > > >
