A "collection" is your data, like newspaper articles or movie titles. It is a user-level concept, not really a Solr design concept.
A "core" is a Solr/Lucene index. It is addressable as solr/collection-name on one machine. You can use a core to store a collection, or you can break it up among multiple cores (usually for performance reasons). When you use a core like this, it is called a "shard". All of the different shards of a collection form the collection. Solr has a feature called Distributed Search that presents the separate shards as if it were one Solr collection. You should set up Distributed Search first. It does not use SolrCloud, but shows you how these ideas work. After that, Solr Cloud will make more sense. Lance On Sat, Jan 22, 2011 at 9:35 AM, Em <mailformailingli...@yahoo.de> wrote: > > Hello list, > > i want to experiment with the new SolrCloud feature. So far, I got > absolutely no experience in distributed search with Solr. > However, there are some things that remain unclear to me: > > 1 ) What is the usecase of a collection? > As far as I understood: A collection is the same as a core but in a > distributed sense. It contains a set of cores on one or multiple machines. > It makes sense that all the cores in a collection got the same schema and > solrconfig - right? > Can someone tell me if I understood the concept of a collection correctly? > > 2 ) The wiki says this will cause an update > -Durl=http://localhost:8983/solr/collection1/update > However, as far as I know this cause an update to a CORE named "collection1" > at localhost:8983, not to the full collection. Am I correct here? > So *I* have to care about consistency between the different replicas inside > my cloud? > > 3 ) If I got replicas of the same shard inside a collection, how does > SolrCloud determine that two documents in a result set are equal? Is it > neccessary to define a unique key? Is it random which of the two documents > is picked into the final resultset? > > --- > I think these are my most basic questions. > However, there is one more tricky thing: > > If I understood the collection-idea correctly: What happens if I create two > cores and each core belongs to a different collection and THEN I do a SWAP. > Say: core1->collection1, core2->collection2 > SWAP core1,core2 > Does core2 now maps to collection1? > > Thank you! > -- > View this message in context: > http://lucene.472066.n3.nabble.com/SolrCloud-Questions-for-MultiCore-Setup-tp2309443p2309443.html > Sent from the Solr - User mailing list archive at Nabble.com. > -- Lance Norskog goks...@gmail.com
