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

Correction: The index has 3.6 million documents.

On Mon, Sep 16, 2024 at 1:00 PM Rui Wu <[email protected]> wrote:

> 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
>