[donboscow]

Yes of course. What I meant is - when I query a phrase, that phrase can be found in one million webpages, yet I get a bunch of them sorted by relevance. Surely that is a combination of two things - deep rooted crawling that gathers data from most websites, and secondly, a nice algorithm to sort them by relevance that is based on a variety of signals. ES has nothing to do with crawling, that is custom to the user using ES, but for the content fed to ES, how much does it allow customizing signals, combining them into a custom relevance logic, and how much does it allow to modify and edit the indexing logic so that say I can use a combination of BM25 and PageRank?

[throw_me_up]

It is very customizable, but signals like PageRank are best calculated outside ES and included as a field in your document.