solr4.0已发布ALPHA版。。离正式版本不久了。。

Solr 4.0-ALPHA was released on 3 Jul 2012 http://t.cn/zWqE2iB

还有两个月。。。出正式版本

列出几个重要的改动跟新增的功能  ：

SolrCloud:

* SOLR-1873, SOLR-2358: SolrCloud - added shared/central config and core/shard management via zookeeper,
  built-in load balancing, and distributed indexing. 

有博文列出：Solr colud”的新功能

函数查询可作结果展示：

* SOLR-1566: Transforming documents in the ResponseWriters.  This will allow
  for more complex results in responses and open the door for function queries
  as results. 

提供更多的函数搜索

* SOLR-2136: Boolean type added to function queries, along with
  new functions exists(), if(), and(), or(), xor(), not(), def(),
  and true and false constants. (yonik)

MultiTermAwareComponent：自动小写对于多term查询（这个暂时没看明）

SOLR-2438 added MultiTermAwareComponent to the various classes to allow automatic lowercasing
  for multiterm queries (wildcards, regex, prefix, range, etc). You can now optionally specify a
  "multiterm" analyzer in our schema.xml, but Solr should "do the right thing" if you don't
  specify <analyzer type="multiterm"> 

返回结果可以更自由，返回函数搜索结果，指定某分片的结果，搜索的explain

* SOLR-1298: Return FunctionQuery as pseudo field.  The solr 'fl' param
  now supports functions.  For example:  fl=id,sum(x,y) -- NOTE: only
  functions with fast random access are reccomended. (yonik, ryan)
  
* SOLR-705: Optionally return shard info with each document in distributed
  search.  Use fl=id,[shard]  to return the shard url.  (ryan)  


* SOLR-2417: Add explain info directly to return documents using 
  ?fl=id,[explain] (ryan)

提供更多的评分规则

* SOLR-2754: Added factories for several ranking algorithms: 
    BM25SimilarityFactory: Okapi BM25
    DFRSimilarityFactory: Divergence from Randomness models
    IBSimilarityFactory: Information-based models
    LMDirichletSimilarity: LM with Dirichlet smoothing
    LMJelinekMercerSimilarity: LM with Jelinek-Mercer smoothing

竞价组件支持分布式

* SOLR-2949: QueryElevationComponent is now supported with distributed search.

竞价组件不使用字段缓存去查找对应的内部luceneid，至于为什么这么做，会不会因为准实时的原因呢？

* SOLR-2950: The QueryElevationComponent now avoids using the FieldCache and looking up
  every document id (gsingers, yonik)

更新文档，可以只提交更新的某几个字段内容，不用提交整个文档

Updateable documents.  JSON Example:
  {"id":"mydoc", "f1":{"set":10}, "f2":{"add":20}}  will result in field "f1"
  being set to 10, "f2" having an additional value of 20 added, and all
  other existing fields unchanged.  All source fields must be stored for
  this feature to work correctly. 

处理器可以为某个字段指定默认值

* SOLR-3495: New UpdateProcessors have been added to create default values for 
  configured fields.  These works similarly to the <field default="..."/> 
  option in schema.xml, but are applied in the UpdateProcessorChain, so they 
  may be used prior to other UpdateProcessors, or to generate a uniqueKey field 
  value when using the DistributedUpdateProcessor (ie: SolrCloud)
    TimestampUpdateProcessorFactory
    UUIDUpdateProcessorFactory
    DefaultValueUpdateProcessorFactory
  (hossman)

删除的json格式更简洁，还可增加optimistic版本号

* SOLR-3508: Simplify JSON update format for deletes as well as allow
  version specification for optimistic locking.  Examples:
    {"delete":"myid"}
    {"delete":["id1","id2","id3"]}
    {"delete":{"id":"myid", "_version_":123456789}}