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Solr 4.0 Release Highlights

ReleaseNote40 – Solr Wiki (via laughingman7743)

Finally some much awaited features in Solr… such as updates to existing records without sending the entire doc again!!

The largest set of features goes by the development code-name “Solr

Cloud” and involves bringing easy scalability to Solr.  


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* Distributed indexing designed from the ground up for near real-time

  (NRT) and NoSQL features such as realtime-get, optimistic locking,

  and durable updates.

* High availability with no single points of failure.

* Apache Zookeeper integration for distributed coordination and

  cluster metadata and configuration storage.

* Immunity to split-brain issues due to Zookeeper’s Paxos distributed

  consensus protocols.

* Updates sent to any node in the cluster and are automatically

  forwarded to the correct shard and replicated to multiple nodes for


* Queries sent to any node automatically perform a full distributed

  search across the cluster with load balancing and fail-over.

* A collection management API.

* Smart SolrJ client (CloudSolrServer) that knows to send documents

  only to the shard leaders

Solr 4.0 includes more NoSQL features for those using Solr as a

primary data store:

* Update durability – A transaction log ensures that even uncommitted

  documents are never lost.

* Real-time Get – The ability to quickly retrieve the latest version

  of a document, without the need to commit or open a new searcher

* Versioning and Optimistic Locking – combined with real-time get,

  this allows read-update-write functionality that ensures no

  conflicting changes were made concurrently by other clients.

* Atomic updates – the ability to add, remove, change, and increment

  fields of an existing document without having to send in the

  complete document again.

Many additional improvements include:

* New spatial field types with polygon support.

* Pivot Faceting – Multi-level or hierarchical faceting where the top

  constraints for one field are found for each top constraint of a

  different field.

* Pseudo-fields – The ability to alias fields, or to add metadata

  along with returned documents, such as function query values and

  results of spatial distance calculations.

* A spell checker implementation that can work directly from the main

  index instead of creating a sidecar index.

* Pseudo-Join functionality – The ability to select a set of

  documents based on their relationship to a second set of documents.

* Function query enhancements including conditional function queries

  and relevancy functions.

* New update processors to facilitate modifying documents prior to


* A brand new web admin interface, including support for SolrCloud

  and improved error reporting

* Numerous bug fixes and optimizations.

Noteworthy changes since 4.0-BETA:

* New spatial field types with polygon support.

* Various Admin UI improvements.

* SolrCloud related performance optimizations in writing the the

  transaction log, PeerSync recovery, Leader election, and

  ClusterState caching.

* Numerous bug fixes and optimizations.