Inline filtered search with adaptive L

[magdalendobson]

This PR implements the recommendation in the filtered search RFC to implement inline filtering with the adaptive L method as an optional addition.

[hildebrandmw]

Thanks Magdalen! In addition to my inline comments - can you also add some integration tests exercising the functionality here? These go a surprisingly long way towards protecting the algorithm.

Also, can we bikeshed InlineSearch a little? Maybe FilteredSearch? Or InlineFilteredSearch? Not a huge deal, but InlineSearch seems a little opaque to me.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 96.25000% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.56%. Comparing base (d44b9a8) to head (8d4194b).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
diskann/src/graph/search/inline_filter_search.rs	94.33%	12 Missing ⚠️
diskann/src/graph/test/cases/inline.rs	98.10%	9 Missing ⚠️
diskann-benchmark/src/inputs/graph_index.rs	80.55%	7 Missing ⚠️
diskann-benchmark/src/backend/index/benchmarks.rs	85.71%	5 Missing ⚠️
diskann-benchmark-core/src/search/graph/inline.rs	98.79%	2 Missing ⚠️
diskann-benchmark/src/backend/index/search/knn.rs	94.44%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1131      +/-   ##
==========================================
+ Coverage   89.45%   90.56%   +1.11%     
==========================================
  Files         484      487       +3     
  Lines       91407    92443    +1036     
==========================================
+ Hits        81765    83722    +1957     
+ Misses       9642     8721     -921     

Flag	Coverage Δ
miri	90.56% <96.25%> (+1.11%)	⬆️
unittests	90.53% <96.25%> (+1.42%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
diskann-benchmark-core/src/search/graph/mod.rs	100.00% <ø> (ø)
...kann-benchmark/src/backend/index/search/plugins.rs	73.58% <100.00%> (+7.58%)	⬆️
diskann-benchmark/src/backend/index/spherical.rs	100.00% <ø> (ø)
diskann-benchmark/src/main.rs	91.26% <100.00%> (+0.09%)	⬆️
diskann/src/graph/search/multihop_search.rs	100.00% <100.00%> (+0.58%)	⬆️
diskann/src/graph/test/cases/multihop.rs	95.79% <100.00%> (ø)
diskann-benchmark/src/backend/index/search/knn.rs	77.77% <94.44%> (+4.16%)	⬆️
diskann-benchmark-core/src/search/graph/inline.rs	98.79% <98.79%> (ø)
diskann-benchmark/src/backend/index/benchmarks.rs	71.22% <85.71%> (+2.43%)	⬆️
diskann-benchmark/src/inputs/graph_index.rs	51.43% <80.55%> (+3.44%)	⬆️
... and 2 more

... and 51 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[magdalendobson]

Thanks Magdalen! In addition to my inline comments - can you also add some integration tests exercising the functionality here? These go a surprisingly long way towards protecting the algorithm.

Also, can we bikeshed InlineSearch a little? Maybe FilteredSearch? Or InlineFilteredSearch? Not a huge deal, but InlineSearch seems a little opaque to me.

I've added some integration test. In addition to throwing some of the existing cases in multihop at it, I also designed a test that should return different results depending on whether or not the adaptive L feature is enabled.

Regarding the naming, I named it InlineSearch to be consistent with MultihopSearch (ie, multihop search isn't called MultihopFilteredSearch either). Should we maybe rename both to mention filtering?

[Copilot]

Pull request overview

This PR adds a new “inline filtered search” path (with optional adaptive L scaling) to the diskann graph search API and wires it through the benchmark harness and test suite.

Changes:

• Introduces InlineSearch + AdaptiveL in diskann/src/graph/search/inline_filter_search.rs and re-exports them from diskann::graph::search.
• Adds end-to-end and algorithm-focused tests for inline filtered traversal behavior.
• Extends diskann-benchmark / diskann-benchmark-core to support a new topk-inline-filter search phase, including an example JSON and integration test.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
diskann/src/graph/test/cases/multihop.rs	Exposes test helpers/filters (pub(super)) for reuse by the new inline test suite.
diskann/src/graph/test/cases/mod.rs	Registers the new inline test module.
diskann/src/graph/test/cases/inline.rs	Adds end-to-end tests for index.search(InlineSearch { .. }), including adaptive-L behavior.
diskann/src/graph/search/multihop_search.rs	Alters scratch initialization (currently introduces a safety/correctness regression if scratch is reused).
diskann/src/graph/search/mod.rs	Adds the inline search module and publicly re-exports InlineSearch/AdaptiveL.
diskann/src/graph/search/inline_filter_search.rs	Implements inline filtered search and adaptive-L sizing; includes unit tests.
diskann-benchmark/src/main.rs	Adds an integration test that runs the new inline-filter example config.
diskann-benchmark/src/inputs/graph_index.rs	Adds TopkInlineFilter search phase + adaptive-L config parsing/validation.
diskann-benchmark/src/backend/index/spherical.rs	Registers and implements the inline-filter search plugin for spherical backend.
diskann-benchmark/src/backend/index/search/plugins.rs	Adds the TopkInlineFilter plugin type/kind mapping.
diskann-benchmark/src/backend/index/search/knn.rs	Adds Knn trait implementation for benchmark_core::search::graph::InlineSearch.
diskann-benchmark/src/backend/index/benchmarks.rs	Registers and implements the inline-filter search plugin for the main backend.
diskann-benchmark/example/graph-index-inline-filter.json	Adds a runnable benchmark example for topk-inline-filter with adaptive_l.
diskann-benchmark-core/src/search/graph/mod.rs	Exposes the new benchmark-core inline graph search helper module/type.
diskann-benchmark-core/src/search/graph/inline.rs	Adds benchmark-core InlineSearch wrapper + tests for inline filtering behavior.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[hildebrandmw]

Thanks Magdalen, my main concern here is getting in decent test coverage using the baseline testing infrastructure. It's more robust than ad-hoc metrics since it can store and validate a lot more information.

Also to bike shed, I do think InlineSearch is a bit vague. Maybe InlineFilteredSearch? Or FilteredKnn?