Your results contain 9 solutions with the following criteria :

Search engines
Solution Smile rating Users rating Popularity
Elasticsearch Elasticsearch 4.0 Smile 4.3 Visitors
46%   Popularity on the site
Flax No rating No rating
6%   Popularity on the site
Lucene Lucene 4.3 Smile No rating
37%   Popularity on the site
LucidWorks No rating No rating
9%   Popularity on the site
Nutch No rating No rating
8%   Popularity on the site
OpenSearchServer OpenSearchServer 3.2 Smile 3.3 Visitors
24%   Popularity on the site
Slor Solr 4.8 Smile 4.0 Visitors
38%   Popularity on the site
Sphinx No rating No rating
10%   Popularity on the site
mnoGoSearch mnoGoSearch 2.3 Smile 4.2 Visitors
11%   Popularity on the site