eZ Find 5.3.0 brings with it a upgrade of Solr to 4.7 and additional features for the new solr version.
The corresponding Exponential custom Solr (elevator helper) request handler (changes in Java API in Solr 4.x)
Addition of the softCommit parameter at appropriate places in the eZ Find classes and ezfind.ini setting
Activation of the transaction log (durability) which will replay non-committed changes upon restart of the Solr backend after a hard crash
Activation of the main index based spell check from 4.x (previously, a dedicated index was built upon commits, which added alot of overhead)
Separation of language dependent part of schema.xml into a dedicated file: makes upgrading and adding new languages much easier
Added analyzer definitions with for most common languages encountered in ezp projects with dedicated stopwords lists and sometimes other analyzer related files: ar, cjk, de, en, es, fi, fr, it, ja, nl, no, pt
Known issue: SolrCloud support is not complete at this moment because the custom request handler talks directly to a given core, not the Solr 4.x 'collection'.