[LUCENE-10624] Binary Search for Sparse IndexedDISI advanceWithinBloc…

[wuwm]

Description (or a Jira issue link if you have one)

https://issues.apache.org/jira/browse/LUCENE-10624

#11660

[zacharymorn]

Thanks @wuwm for opening this PR! The improvement idea makes sense to me. Quick question though, given the similarities of the binary search implementations in the two methods, is it possible to extract them out into a common method?

[wuwm]

Thanks @zacharymorn for comments!

There are some implementation diff inside binary search between two methods to handle some edge cases. To make binary search into a single common method, I thought of two ways: A) Add a lambda expression as method parameter to pass in implementation diff part. B) Add if-else to the combined single method. I felt both of them may make readability worse?

Also, I feel, for future changes, since these two methods serve different use cases, future optimization may vary as well (Not an expert in this part, feel free to correct me). Combing into a common method might make future changes complex.

[zacharymorn]

Hmm I see. I'm actually also wondering if it will be possible to have one of them simply delegate to the other one (potentially indirectly via some helper method), and then check the returned value (e.g. have advanceExactWithinBlock to delegate somehow to advanceWithinBlock and then check if the positioned doc is actually equal to target)?

[yuzhoujianxia]

Can we get this merged?

[wuwm]

@yuzhoujianxia There are some discussion on if binary or exponential search can cause performance regression in some use cases. We need to address the concerns before merging. https://issues.apache.org/jira/browse/LUCENE-10624

[mikemccand]

This sounds like a nice optimization @wuwm! Is it still relevant?

Lucene's nightly benchmarks include somewhat sparse documents (NYC taxi database) -- maybe this could be used to test the impact of exponential vs full binary search?

[github-actions]

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