just saw this email in my spam (grr GMail!) -- I agree, we should do a 10.5.2 release to fix this. I can be release manager. Is there anything else we'd need to include?
On Thu, Aug 27, 2026 at 12:25 PM Ethan Baker <[email protected]> wrote: > > Hi all, > > It seems that the changes introduced in 10.5.1 revealed a dormant bug that > can silently regress KNN recall 5-7% (#16552 [1]), and I'm wondering if the > community agrees this warrants a second bugfix release for 10.5. > > Some background on the bug: #15003 [2] added support for HNSW re-use across > merges for segments with deletes in 10.4.0, but re-use was silently disabled > under per-field codecs the whole time, until #16400 [3] fixed it in 10.5.1. > The issue is that this 're-use with deletes' path that is now enabled had a > latent bug, which skipped repairing nodes where connections deteriorated > slowly over many merges. After many repeated merges on segments with low > delete percents, connections continue to erode, and this bug ends up reducing > out-degree 40+% and dropping recall by an observed 5-7%. > > The bug was fixed in #16559 [4], but this seems like a big drop in recall > that should be resolved quickly. Assuming others agree it's needed, would > anyone more experienced than me be willing to help release such a patch? > > Thanks, > Ethan > > [1] https://github.com/apache/lucene/issues/16552 > [2] https://github.com/apache/lucene/pull/15003 > [3] https://github.com/apache/lucene/issues/16400 > [4] https://github.com/apache/lucene/pull/16559 --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
