We are building a university website and finding a search solution for it. Our university website has high-traffic because it has faculty of open university so very much students (approximately 1.5 million). Even we use caching for speeding up the website. Anyway, which search engine do you suggest for our situation?
Note: We think Solr, Elasticsearch or Sphinx for now, but also it can be one of the others.
Update: We need a full-text search engine which must be fast, extendable and with the features like query likening and indicating priority support.
Thanks.