A common pattern is to materialise views, that is store the join at the same time you are writing to CF's A and B.
In this case it sounds like the two CF's are written to at different times. If that is the case you may need to do the join client side (do two reads). Hope that helps. ----------------- Aaron Morton Freelance Cassandra Consultant New Zealand @aaronmorton http://www.thelastpickle.com On 27/05/2013, at 6:56 PM, Vegard Berget <p...@fantasista.no> wrote: > Hi, > > I am no expert, but a couple of suggestions: > 1) Remember that writes are very fast i Cassandra, so don't be afraid to > store more information than you would in an Sql-ish server. > 2) It would be better with an example, but again - by storing more than you > would in an sql-schema, would you still need to compute a table C? Is it > possible to have just the CF A, and have all data in that CF? Would it be > possible/easier to have the rules applied on the client, so that you don't > have to change the schema/recalculate CF C? > > .vegard, > > ----- Original Message ----- > From: > user@cassandra.apache.org > > To: > <user@cassandra.apache.org> > Cc: > > Sent: > Sat, 25 May 2013 15:22:00 -0700 > Subject: > how to handle join properly in this case > > > Hi Experts, > > We have tables (a.k.a. column family) A and B. The row of the table is > simply a key value pair. Table A and B are written by clients all the > time. We need to transform the row key of table A and B according to > a set of rules, join these two tables and save the results to table C > for read. > > Questions > 1) Schema like this is very close to a schema in SQL. We mainly want > to separate read and write operations by different column families. Is > this a correct way to model the join in Cassandra? > > 2) If the rules change a little bit, which is quite possible, we will > have to drop table C, and recompute the join result, which seems to be > cumbersome because not all the join results need to be changed, just > some of them. Are there any better ways to handle such change? > > Thanks a lot. > > > -- > Regards, > Jiaan
