Hm, I'm not totally following, but... would you have to recalculate all row values every time the corpus changes? I guess that could work for a seldom-changing corpus, not sure how popular a use case that is. I suspect most people would not be interested in such an approach, instead either making do without TF/IDF, or moving to a non-pg solution.
> Yep, I mean this is always the case for corpus-level algos right?
I am not sure which parts of which calculations lucene (Elastic Search and Solr) does on the fly vs pre-calculates after any change to corpus, because it's more or less transparent. I mean, I guess that's not entirely true -- there are definitely index-rebuilds that happen after updates, and for larger-scale things they can be resource-intensive enough that you have to account for them (for very small-scale things you can more or less ignore them), maybe it's just that Solr/ES have architectures built around accounting for that and giving you tools to deal with it with various approaches.
