[karmakaze]

Another resource is a trigram search index (in Go) used by etsy/hound[0] based on an article (and code) from Russ Cox: Regular Expression Matching with a Trigram Index[1].

[0] https://github.com/hound-search/hound

[1] http://swtch.com/~rsc/regexp/regexp4.html

Different use-cases for alternatives to Lucene depending on your needs.