I think it makes more sense to compare it with Lucene (which both ElasticSearch and Solr are based on) or, say, Xapian. Based on a PDF http://grupoweb.upf.es/W

I think it makes more sense to compare it with Lucene (which both ElasticSearch and Solr are based on) or, say, Xapian. Based on a PDF http://grupoweb.upf.es/WRG/mir2ed/pdf/slides_appendixA.pdf http://grupoweb.upf.es/WRG/mir2ed/pdf/slides_appendixA.pdf page 14 (linked from http://stackoverflow.com/q/5028314/116546 http://stackoverflow.com/q/5028314/116546), I think the differences are MG4J has constant RAM usage (as opposed to Lucene's linear one), but is somewhat more CPU intensive. Haven't used either directly.