Refactor(diskann-benchmark): consolidate disk search config under DiskSearchMode

[dyhyfu]

Summary

Consolidates disk-index search configuration under DiskSearchMode and decouples the benchmark's JSON input schema from the optional diskann-disk backend.

Previously, the input schema both defined the config and constructed diskann_disk::SearchMode, forcing several #[cfg(feature = "disk-index")] gates and scattering related fields (vector_filters_file, post_processor) across DiskSearchPhase. This PR moves the backend-specific construction into the search execution path and groups the search-mode fields together.

Changes

• Move SearchMode construction to the backend. The match logic that builds diskann_disk::SearchMode now lives in a build_search_mode helper in the search execution module, so the input schema is pure config data with no dependency on the disk backend's SearchMode type.
• Consolidate fields into DiskSearchMode. vector_filters_file and post_processor are nested inside DiskSearchMode alongside is_flat_search and adaptive_l. Validation and Display moved accordingly.
• Remove unnecessary feature gates. DiskSearchMode and its fields no longer need #[cfg(feature = "disk-index")]. The only remaining gates are for QuantizationType, which is a diskann-disk type (intentionally left as-is — see below).
• Migrate JSON fixtures (examples and perf test inputs) to the nested search_mode format.

[Copilot]

Pull request overview

This PR refactors the diskann-benchmark disk-index benchmark input schema to consolidate disk search configuration under DiskSearchMode, and moves diskann_disk::SearchMode construction out of the JSON schema layer into the disk search execution path.

Changes:

• Nested vector_filters_file and post_processor under DiskSearchMode, alongside is_flat_search and adaptive_l, and moved validation accordingly.
• Added a build_search_mode helper in disk_index/search.rs to construct backend SearchMode at execution time.
• Updated benchmark JSON fixtures (examples + perf inputs) to the new nested search_mode format.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
diskann-benchmark/src/inputs/disk.rs	Refactors disk-index JSON schema to centralize mode-specific config/validation in DiskSearchMode.
diskann-benchmark/src/disk_index/search.rs	Builds backend SearchMode during execution using new helper; updates access paths to nested config.
diskann-benchmark/perf_test_inputs/wikipedia-100K-disk-index.json	Migrates perf input to nested search_mode object.
diskann-benchmark/perf_test_inputs/openai-100K-disk-index.json	Migrates perf input to nested search_mode object.
diskann-benchmark/example/disk-index.json	Migrates example input to nested search_mode object.
diskann-benchmark/example/disk-index-filter.json	Migrates filter example to nested search_mode.vector_filters_file.
diskann-benchmark/example/disk-index-determinant-diversity.json	Migrates post-processor example to nested search_mode.post_processor.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 77.94118% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.15%. Comparing base (3c8728c) to head (ca59956).

Files with missing lines	Patch %	Lines
diskann-benchmark/src/inputs/disk.rs	77.94%	15 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1232      +/-   ##
==========================================
- Coverage   91.16%   90.15%   -1.01%     
==========================================
  Files         509      509              
  Lines       97093    97160      +67     
==========================================
- Hits        88510    87598     -912     
- Misses       8583     9562     +979     

Flag	Coverage Δ
miri	90.15% <77.94%> (-1.01%)	⬇️
unittests	89.82% <77.94%> (-1.30%)	⬇️

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Files with missing lines	Coverage Δ
diskann-benchmark/src/main.rs	91.64% <ø> (ø)
diskann-benchmark/src/inputs/disk.rs	20.36% <77.94%> (+18.92%)	⬆️

... and 40 files with indirect coverage changes

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[suri-kumkaran]

Can we use a enum here to avoid impossible combinations? Something similar and in spirit of:

pub enum SearchMode<'a> {
    FlatScan {
        filter: Option<SearchPredicate<'a>>,
    },

    Graph {
        filter: Option<SearchPredicate<'a>>,
    },

    InlineFilter {
        filter: Box<dyn QueryLabelProvider<u32> + 'a>,
        adaptive_l: Option<AdaptiveL>,
    },

    DiverseGraph {
        filter: Option<SearchPredicate<'a>>,
        params: DeterminantDiversityParams,
    },
}

I understand SearchMode is per query and has relevant types, but can we have something similiar on the benchmark input level eliminating the impossible scenarios?