MaxScoreBulkScorer increased latency for a extreme test case (many SHOULD and each SHOULD clause matches all docs)

Dear experts,

In our Mongodb Atlas Search performance regression test between Lucene 9.7
and Lucene 9.11, we detect a 43% latency regression in this query shape:
12 SHOULD clause, and each clause matches all of the documents. Each should
clause is wrapped in ConstantScoreQuery.

The index has 3.6 documents, and every document is identical: Every
document is {"path": ["1", "2", "3" ... "12"]}
The query shape is a BooleanQuery of SHOULD "1", SHOULD "2", ... SHOULD
"12".

Our flamegraphs show that most of the time in search() is spent on
the MaxScoreBulkScorer class:
[image: image.png]

We wonder if this extreme test case is expected to be slow on
MaxScoreBulkScorer?

Thanks a lot!

Rui Wu
Lead Engineer, MongoDB