feat(duckdb): report per-file column statistics from the vortex COPY writer

[moshap-firebolt]

Rationale for this change

DuckDB's COPY hook copy_to_get_written_statistics lets a writer return WRITTEN_FILE_STATISTICS. The vortex COPY function didn't implement it, so COPY … (FORMAT vortex, RETURN_STATS) failed at bind (RETURN_STATS is not supported for the "vortex" copy format) and callers such as DuckLake could not record per-column statistics or enforce NOT NULL on vortex columns.

• Closes Implement copy_to_get_written_statistics for DuckDB COPY function #7819

What changes are included in this PR?

• Implement copy_to_get_written_statistics for the vortex COPY function, following the parquet writer's store-pointer-then-fill-at-finalize pattern. This makes COPY … (FORMAT vortex, RETURN_STATS) work.
• Per file: row_count, file_size_bytes. Per column: min/max, null_count, num_values, has_nan (float columns), and column_size_bytes (on-disk compressed size; excludes bytes not attributable to a column, so per-column sizes do not sum to the file size). Only top-level columns are reported — the footer exposes one statistics set per top-level field.
• Statistics are read from the WriteSummary that copy_to_finalize previously dropped; no file is re-opened. A scalar-conversion failure is surfaced through the copy function's error channel rather than swallowed as "no statistics".
• e2e tests drive COPY … RETURN_STATS through DuckDB and assert the returned file statistics (including that nested struct/list columns do not crash the hook); a plain COPY without RETURN_STATS is unchanged.

What APIs are changed? Are there any user-facing changes?

Yes — COPY … (FORMAT vortex, RETURN_STATS) starts working (previously a bind-time error). Internally, two new C FFI entry points and two FFI structs; vortex.h is regenerated. No public Rust API changes.

[codspeed-hq]

Merging this PR will degrade performance by 11.59%

⚠️ 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.

❌ 1 regressed benchmark
✅ 1980 untouched benchmarks
⏩ 54 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	cold_misaligned[(16, 64)]	380.2 µs	430.1 µs	-11.59%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing feat/rtdl-written-statistics-upstream (522eba4) with develop (e4b3421)}

Footnotes

1. 54 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. ↩

[myrrc]

Thanks for the contribution. The changes mostly look good but let's remove some comments and add some others :)

[myrrc]

Let's fix the rest comments and the tests, and the PR is good to go

[myrrc]

Good! Let's fix the test and merge this.