Hi Adrien, Thanks for your help and putting up a fix!
Another experiment I did without your PR: if the 12 SHOULD clauses are changed to 12 MUST clauses, the problem is the same: it collects 3.6M docs on Lucene911 but 1001 docs on Lucene97. Does this data point align with how MaxScoreBulkScorer works? Thanks! On Wed, Sep 18, 2024 at 1:51 AM Adrien Grand <jpou...@gmail.com> wrote: > Thank you, this last comment was helpful and helped me understand the > problem. I opened a PR at https://github.com/apache/lucene/pull/13800. > > On Tue, Sep 17, 2024 at 7:45 PM Rui Wu <rui...@mongodb.com> wrote: > >> Another information is that, in Lucene97, this query (12 SHOULD clauses) >> collected 1001 results; while in Lucene911, this query (12 SHOULD clauses) >> collected all docs (3.6M collect count). >> >> In Lucene911, if the query has only one SHOULD clause, it collects 1001 >> results. If the query has multiple clauses, it collects 3.6M results. >> >> On Tue, Sep 17, 2024 at 9:09 AM Rui Wu <rui...@mongodb.com> wrote: >> >>> This query latency increased from 14.65 to 20.90ms. >>> >>> We use the `TopScoreDocCollector.createSharedManager(/*batchSize*/ 101, >>> /*searchAfterFieldDoc*/ null, /*hitsThreshold*/ 1000); ` >>> >>> Thanks a lot! >>> >>> On Tue, Sep 17, 2024 at 6:45 AM Adrien Grand <jpou...@gmail.com> wrote: >>> >>>> Can you tell us how long this query used to take, and how long it >>>> takes now? >>>> Also are you using IndexSearcher's default total hit count threshold of >>>> 1,000, or are you passing a custom value to TopScoreDocCollectorManager? >>>> >>>> On Tue, Sep 17, 2024 at 10:14 AM Rui Wu <rui...@mongodb.com> wrote: >>>> >>>>> Hi Adrien, >>>>> >>>>> Thanks for looking into this! Here are more screenshots of the >>>>> flamegraph. The original flamegraph HTMLs have stack traces from our app >>>>> so >>>>> I don't share it here. >>>>> [image: Screenshot 2024-09-17 at 1.13.07 AM.png][image: Screenshot >>>>> 2024-09-17 at 1.12.01 AM.png] >>>>> >>>>> On Tue, Sep 17, 2024 at 1:00 AM Adrien Grand <jpou...@gmail.com> >>>>> wrote: >>>>> >>>>>> Hello Rui, >>>>>> >>>>>> We actually released a change that should make MaxScoreBulkScorer >>>>>> faster on dense disjunctions in 9.8: >>>>>> https://github.com/apache/lucene/pull/12444. Your benchmark case is >>>>>> quite specific though as all clauses match all docs and produce constant >>>>>> scores, so I would expect the scorer to quickly realize that it can skip >>>>>> all documents once it's scored the first k docs. This makes me wonder if >>>>>> it >>>>>> bottleneck on skipping blocks of documents rather than on scoring them. >>>>>> Would you be able to share your whole flame graph, it looks like it may >>>>>> be >>>>>> truncated a the top? >>>>>> >>>>>> On Mon, Sep 16, 2024 at 10:01 PM Rui Wu <rui...@mongodb.com> wrote: >>>>>> >>>>>>> Correction: The index has 3.6 million documents. >>>>>>> >>>>>>> On Mon, Sep 16, 2024 at 1:00 PM Rui Wu <rui...@mongodb.com> 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 >>>>>>>> >>>>>>> >>>>>> >>>>>> -- >>>>>> Adrien >>>>>> >>>>> >>>> >>>> -- >>>> Adrien >>>> >>> > > -- > Adrien >
