Please start separate threads for separate q On Fri, May 25, 2012 at 6:30 AM, Nicholas Ball <nicholas.b...@nodelay.com> wrote: > > Hey all, > > I have another question with regards to this thread. > > Does anyone know what the state is of the rollback command in 4.0 and how > it works with both; replicas (i.e. distributed rollbacks) and the snapshot > isolation implemented (i.e. timestamps reverted?), the relevant class is > DistributedUpdateProcessor but not sure if I'm missing something. Has this > been implemented? > > Cheers, > Nicholas > > On Thu, 24 May 2012 09:53:23 -0600, Nicholas Ball > <nicholas.b...@nodelay.com> wrote: >> Thanks for the link, will investigate further. On the outset though, it >> looks as though it's not what we want to be going towards. >> Also note that it's not open-sourced (other than Solandra which hasn't >> been updated in aaaages https://github.com/tjake/Solandra). >> >> Rather than build on top of Cassandra, the new NRT + transaction log > Solr >> features really make it more of a possibility to make Solr into a >> NoSQL-like system and possibly with better transactional guarantees than >> NoSQL! >> >> Speaking to yonik has given me more information on this. Currently, > there >> is an optimistic lock-free mechanism on a per-document basis only as for >> most, documents only live on a single logical shard. It essentially > checks >> the _version_ you send in for a document against the latest version for > the >> document it has. >> >> I propose an additional feature to this for those who want to have such >> guarantees spanning over multiple documents living on various shards. In > my >> use-case, I have shards holding documents that point to other shards. In >> this case, an update would need to be an atomic transaction spanning > over >> various documents on various shards. Would anyone object to having this >> functionality added to Solr if I were to contribute it? >> >> Many thanks, >> Nicholas >> >> On Thu, 24 May 2012 08:16:25 -0700, Walter Underwood >> <wun...@wunderwood.org> wrote: >>> You should take a look at what DataStax has already done with Solr and >>> Cassandra. >>> >>> > http://www.datastax.com/dev/blog/cassandra-with-solr-integration-details >>> >>> wunder >>> >>> On May 24, 2012, at 7:50 AM, Nicholas Ball wrote: >>> >>>> >>>> Hey all, >>>> >>>> I've been working on a SOLR set up with some heavy customization > (using >>>> the adminHandler as a way into the system) for a research project @ >>>> Imperial College London, however I now see there has been a > substantial >>>> push towards a NoSQL. For this, there needs to be some kind of >>>> optimistic >>>> fine-grained concurrency control on updates. As we have document >>>> versioning >>>> in-built into Lucene (and therefore Solr) this shouldn't be too >>>> difficult, >>>> however the push has been more of a focus on single core optimistic >>>> LOCKING. >>>> >>>> I would like to take this toward a multi-core (and multi-node) >>>> distributed >>>> optimistic lock-free mechanism. This is gives us the ability to > provide >>>> stronger guarantees than NoSQL wrt distributed transaction isolation >> and >>>> as >>>> we can now do soft-commits, we can also provide specific version >>>> rollbacks >>>> (http://java.dzone.com/articles/exploring-transactional-0). Some more >>>> interesting reading on this topic: (read-)snapshot isolation >>>> (http://pages.cs.wisc.edu/~cs764-1/critique.pdf) and even stronger >>>> guarantees with a slight performance hit with write-snapshot isolation >>>> (http://www.fever.ch/usbkey_eurosys12/papers/p155-yabandehA.pdf). >> People >>>> are starting to realize that we don't have to sacrifice guarantees for >>>> better performance and scalability (like NoSQL) but rather relax them >>>> very >>>> minimally. >>>> >>>> What I need is for someone to shed some light on this feature and the >>>> future plans of Solr wrt this is? Am I correct in thinking that a >>>> multiversion concurrency control (MVCC) locking mechanism now exist > for >> a >>>> single core or is it lock-free and multi-core? >>>> >>>> Many thanks, >>>> Nicholas Ball (aka incunix) >>> >>> -- >>> Walter Underwood >>> wun...@wunderwood.org
-- Lance Norskog goks...@gmail.com
