jpountz opened a new pull request, #12589:
URL: https://github.com/apache/lucene/pull/12589
The idea behind MAXSCORE is to run disjunctions as `+(essentialClause1 ...
essentialClauseM) nonEssentialClause1 ... nonEssentialClauseN`, moving more and
more clauses from the essential list to the non-essential list as the minimum
competitive score increases. For instance, a query such as `the book of life`
which I found in the Tantivy benchmark ends up running as `+book the of life`
after some time, ie. with one required clause and other clauses optional. This
is because matching `the`, `of` and `life` alone is not good enough for
yielding a match.
Here some statistics in that case:
- min competitive score: 3.4781857
- max_window_score(book): 2.8796153
- max_window_score(life): 2.037863
- max_window_score(the): 0.103848875
- max_window_score(of): 0.19427927
Actually if you look at these statistics, we could do better, because a
match may only be competitive if it matches both `book` and `life`, so this
query could actually execute as `+book +life the of`, which may help evaluate
fewer documents compared to `+book the of life`. Especially if you enable
recursive graph bisection.
This is what this PR tries to achieve: in the event when there is a single
essential clause and matching all clauses but the best non-essential clause
cannot produce a competitive match, then the scorer will only evaluate
documents that match the intersection of the essential clause and the best
non-essential clause.
It's worth noting that this optimization would kick in very frequently on
2-clauses disjunctions.
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