Version 2.0 of Couchbase Server has been released with a new flexible document data model that will give more freedom for developing apps.

The document data model in the new version of the NoSQL database is based on JSON, and avoids the need to create and manage schemas. Every JSON document can have a different record structure and multiple documents with different structures can be stored in the same Couchbase data bucket. Document structure can be changed at any time, without requiring modification to other documents in the database.

Distributed indexing and querying has also been added for JSON documents. This will mean you can give users access to stored data via queries. Indexes are defined using design documents and views, and you create design documents on a per-bucket basis, with each design document optionally containing multiple views. Each view includes a Map and optionally a Reduce function, both written in Javascript. Once a view is defined, you can query data using this materialized view and look up information based on various filters.

Views in Couchbase are built asynchronously and are eventually indexed, but not immediately, though there is an option to control this behavior on a per operation basis. Couchbase distributes indexes across the cluster - each node indexing the data it holds. When the view is being built, the JavaScript map function is applied across every document on every node and the key value pairs for matching documents are retrieved and stored in the index.

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Other improvements to the new version are aimed at more traditional areas of interest. Cross datacenter replication (XDCR) has been added, so that you get automatic replication of databases across geographically disparate data centers. Couchbase says this will improve application response time by locating data closer to the users accessing it. There have also been a number of operational enhancements, such as online data and index compaction, that improve Couchbase Server’s application maintenance.

Couchbase Server 2.0 is available in both Enterprise and Community editions, the former a production-ready release with support and bug fixes for funded projects and the latter for enthusiasts who are able to resolve issues independently with help from the Couuchbase user community.  For Linux there are versions for 64-bit and 32-bit Ubuntu and 64-bit and 32-bit Red Hat. Both editions are available for 64-bit Windows but for Mac OS X there is only a 64-bit Community edition.

 here: http://www.couchbase.com/download