Solr 5.2.0 发布，值得关注的改进如下：
Restore API allows restoring a core from an index backup.
JSON Facet API
unique() is now implemented for numeric and date fields
Optional flatter form via a "type" parameter
Added support for "mincount" parameter in range facets to suppress buckets less than that count
Multi-select faceting support for the Facet Module via the "excludeTags" parameter which disregards any matching tagged filters for that facet.
hll() facet function for distributed cardinality via HyperLogLog algorithm. See examples at http://yonik.com/solr-count-distinct/
A new "facet.range.method" parameter to let users choose how to do range faceting between an implementation based on filters (previous algorithm, using "facet.range.method=filter") or DocValues ("facet.range.method=dv")
Rule-based Replica assignment during collection, shard, and replica creation.