We do pretty much the same thing here, dynamic column with a timestamp for column name and a different value type for each row. We use the serialization/deserialization classes provided with Hector and store the type of the value in the key of the row. Example of row key: "b6c8a1e7281761e62230ea76daa3d841#INT" => every values are Integer "7f30a6a2bbb1b921afc8216d8c5d9257#DOUBLE" => every values are Double .... If I'll have to do it again, I'll try to use (Dynamic)CompositeType for value or an equivalent mechanism as suggested by Roland.
On 3 July 2011 15:07, Roland Gude <[email protected]> wrote: > You could do the serialization for all your supported datatypes yourself > (many libraries for serialization are available and a pretty thorough > benchmarking for them can be found here: > https://github.com/eishay/jvm-serializers/wiki) and prepend the serialized > bytes with an identifier for your datatype. > This would not avoid casting though but would still be better performing > then serializing to strings as it is done in your example. > Prepending the values with the id seems to be better to me, because you can > be sure that a new insertion to some field overwrites the correct column > even if it changed the type. > > -----Ursprüngliche Nachricht----- > Von: osishkin osishkin [mailto:[email protected]] > Gesendet: Sonntag, 3. Juli 2011 13:52 > An: [email protected] > Betreff: Multi-type column values in single CF > > Hi all, > > I need to store column values that are of various data types in a > single column family, i.e I have column values that are integers, > others that are strings, and maybe more later. All column names are > strings (no comparator problem for me). > The thing is I need to store unstructured data - I do not have fixed > and known-in-advacne column names, so I can not use a fixed static map > for casting the values back to their original type on retrieval from > cassandra. > > My immediate naive thought is to simply prefix every column name with > the type the value needs to be cast back to. > For example i'll do the follwing conversion to the columns of some key - > {'attr1': 'val1','attr2': 100} ~> {'str_attr1' : 'val1', 'int_attr2' : > '100'} > and only then send it to cassandra. This way I know to what should I > cast it back. > > But all this casting back and forth on the client side seems to me to > be very bad for performance. > Another option is to split the columns on dedicated column families > with mathcing validation types - a column family for integer values, > one for string, one for timestamp etc. > But that does not seem very efficient either (and worse for any > rollback mechanism), since now I have to perform several get calls on > multiple CFs where once I had only one. > > I thought perhaps someone has encountered a similar situation in the > past, and can offer some advice on the best course of action. > > Thank you, > Osi > > >
