[claude] benchmarks-website v3: per-group descriptions + partial-coverage commits

[connortsui20]

Two independent fixes for the v3 server, on the same branch.

Task A — per-group hover descriptions

Port v2's BENCHMARK_DESCRIPTIONS + getBenchmarkDescription strings into the v3 server.

• New description: Option<String> field on Group and GroupChartsResponse, populated from a small hand-maintained table in api/descriptions.rs. Strings match v2 verbatim where v2 had one (Random Access, Compression, Compression Size, Clickbench, StatPopGen, PolarSignals).
• TPC-H / TPC-DS descriptions are derived from the parsed group name so there's no need for one entry per (storage, sf) pair. TPC-H carries the ~XGB of data annotation (SF=1 → 1GB, SF=10 → 10GB, etc.); TPC-DS does not, matching v2 verbatim.
• Vector-search groups have no canonical description in v2, so the icon is omitted for those rather than fabricated.

Render path:

• Landing page: a small ⓘ icon (.group-info-icon, cursor-help) next to every group title, surfacing the description via a CSS-only [data-tooltip]::after pseudo-element. Visible on hover and on focus; the icon is tabindex="0" role="note" with aria-label set so it's reachable via keyboard and to screen readers.
• /group/{slug} permalink page: same icon next to the chart-meta header.

Task B — render commits with partial / missing series data

Symptom: charts had invisible gaps where commits should be. Diagnosis:

1. SeriesAccumulator::ensure_commit only registered a commit after a series produced a row, so commits with zero rows in the chart's fact table were silently dropped from commits[].
2. The client renderer set spanGaps: true on every dataset, so surviving nulls were drawn over as continuous lines.

Server fix. Each collect_*_chart now seeds the accumulator with a canonical commits-dim pre-pass scoped to every commit in the requested CommitWindow whose timestamp is at or after the earliest commit that has a row in this chart's fact table. That bounded form keeps two things right:

• Commits with zero fact-table rows still appear in commits[]; their per-series slot stays null and (with the client fix) renders as a visible gap.
• Commits older than the chart's first fact-table row are excluded — we never render pre-history before the benchmark even existed.

The accumulator now exposes seed_commits + commit_idx(sha); the per-fact-table SQL is unchanged shape-wise but no longer carries c.timestamp/message/url (the seeded set already has those).

Client fix. spanGaps: false on every dataset in chart-init.js, so missing measurements show up as a real break in the line. The external tooltip already cleanly skipped null rows via .filter(Boolean) — preserved. LTTB still operates on the union of non-null x-positions and skips downsampling when the union ≤ MAX_VISIBLE_POINTS, so a sparse series with a handful of non-null values across hundreds of commits still renders all of them as connected points.

Bumped STATIC_ASSET_VERSION from bench-v3-ui-17 → bench-v3-ui-18 so cached browsers see the new bytes.

Tests

New server/tests/web_ui.rs covers both tasks:

Task A:

• landing_page_renders_group_descriptions — verbatim v2 strings + the SF-derived TPC blurb both appear on /.
• group_page_renders_description — same icon on /group/{slug}.
• vector_search_group_has_no_description_icon — no canonical description ⇒ no icon.
• groups_api_carries_description_field — wire shape: description field present where v2 had one, absent for vector-search groups.

Task B:

• chart_includes_commits_with_partial_series_coverage — the headline regression test: commits A (X+Y), B (only Y), C (X+Y); B appears in commits[] with null for X.
• chart_includes_commits_with_zero_rows_in_fact_table — a commit that emitted only compression_size still appears on the random-access chart's x-axis.
• chart_excludes_commits_before_first_fact_row — commits older than the bench's first row stay off the chart.

Plus unit tests in api/descriptions.rs for the static-vs-derived dispatch and the SF parser edge cases.

Conventions

• Branched from ct/benchmarks-v3, PR'd back to it.
• Every commit has a Signed-off-by: trailer.
• Don't auto-merge — leaving for review.
• Local cargo build was hitting environment issues (target-dir lock contention); skipped in favour of GitHub Actions for the canonical Rust checks. The Rust changes are mechanical (new module, new field on existing structs, refactor of collect_*_chart to a seed-then-fill pattern) and well-covered by the new tests above.

Test plan

• CI green (cargo test -p vortex-bench-server, fmt, clippy on touched code) — tracked by GitHub Actions.
• Open landing page, hover a group title's ⓘ → description appears below the icon.
• Tab to a group title's ⓘ → description still appears (focus path).
• Visit /group/<slug> for Random Access → description renders next to chart count.
• Find a chart with known partial coverage; confirm previously-missing commits now appear with visible gaps in the affected series.

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Generated by Claude Code

[codspeed-hq]

Merging this PR will improve performance by 27.62%

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

⚡ 2 improved benchmarks
✅ 1167 untouched benchmarks
⏩ 138 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	varbinview_zip_fragmented_mask	7.3 ms	6.5 ms	+11.46%
⚡	Simulation	varbinview_zip_block_mask	3.7 ms	2.9 ms	+27.62%

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_{Comparing claude/benchmarks-v3-descriptions-and-gaps (c05d035) with ct/benchmarks-v3 (afec890)}

Footnotes

1. 138 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩