Hi Keith, Do you know exactly how an algorithm should be in order to fit in the MapReduce framework? Could you refer me to some references?
Thanks and Regards, Mahsa On Tue, Mar 13, 2012 at 12:49 PM, Keith Wiley <kwi...@keithwiley.com> wrote: > https://cwiki.apache.org/Hive/languagemanual-joins.html > > "Hive does not support join conditions that are not equality conditions as > it is very difficult to express such conditions as a map/reduce job." > > I admit, that isn't a very detailed answer, but it gives some indication > of the reason for the discrepancy between Hive and other databases. Hive > fundamentally operates on Hadoop, namely on MapReduce (we all know this, > I'm just reiterating the train of thought). The problem is that certain > algorithms are exceedingly difficult to wedge into the MapReduce framework. > > That is as detailed as my personal insight can get. I've done a lot of > MapReduce programming in Hadoop but I'm not a database expert and I don't > really understand the steps involved in various kinds of table-joins, so I > don't understand the particular ways in which certain database operations > do or do not fit into MapReduce...but presumably nonequality joins > (whatever those are :-D ) are particularly difficult to MapReduceify. > > Cheers! > > On Mar 13, 2012, at 09:17 , mahsa mofidpoor wrote: > > > Hello, > > > > Is there a reason behind not implementing non-equality joins in Hive? In > other words, is there any usage for theta-join, if implemented? > > > > Thank you in advance for your response, > > Mahsa > > > > ________________________________________________________________________________ > Keith Wiley kwi...@keithwiley.com keithwiley.com > music.keithwiley.com > > "It's a fine line between meticulous and obsessive-compulsive and a > slippery > rope between obsessive-compulsive and debilitatingly slow." > -- Keith Wiley > > ________________________________________________________________________________ > >
