Yes I think these are right. Try my latest committed change. Since the table only stores one entry for an item-item pair, with the lower key first, the union in getDiffSQL is not needed, with a small change to the calling code. But then a union is needed in the other statement. I believe the union I've put in works since it will still result in the right ordering.
If you have some time to test it, that'd be quite useful. On Wed, Jan 26, 2011 at 3:46 PM, Eric Sellin <[email protected]> wrote: > Hello all, > > I am looking at the Mahout 0.4 code for MySQLJDBCDiffStorage in the > Slope One recommender, and in particular the first two SQL statements. > > In the getDiffSQL statement, isn't it missing the stdevColumn in the > second SELECT of the UNION, and more importantly, shouldn't the > avgColumn in that same second SELECT have a minus sign in front of it? > > In the getDiffsSQL statement, aren't we simply missing a UNION with a > second SELECT that looks for our particular item in the A column rather > than the B column like the first SELECT does? > > I may have got this completely wrong, please do let me know! > > Regards, > Eric. > > > >
