Part of the way down the post links to Russ Cox's excellent writeup of how Google used this general sort of technique (turn a regexp into a bunch of conditions

Part of the way down the post links to Russ Cox's excellent writeup of how Google used this general sort of technique (turn a regexp into a bunch of conditions involving three-symbol sequences, search an index for them, work from there) to do regexp searching scalably for Code Search: https://swtch.com/~rsc/regexp/regexp4.html https://swtch.com/~rsc/regexp/regexp4.html You can peruse his open-source (re)implementation of the approach at https://github.com/google/codesearch https://github.com/google/codesearch .