Add RunEndBool encoding for efficient boolean array compression

[joseph-isaacs]

Summary

This PR introduces a new RunEndBool encoding specialized for compressing boolean arrays with long runs. Since boolean values strictly alternate in run-end encoding, we can store only the run end positions plus a single start flag, rather than maintaining a separate values array like the generic RunEnd encoding.

Changes

1. New vortex-runend-bool crate with:

   • RunEndBoolArray type and metadata serialization
   • Specialized compression/decompression for boolean runs
   • Compute kernels: filter, take, invert, is_constant, is_sorted, min_max
   • Scalar access and slicing operations
   • Efficient run-preserving filtering that merges adjacent runs with identical values

2. Self-contained run-end indexing — RunEndBool implements its own find_physical_index / find_slice_end_index (ctx-based, mirroring vortex-runend's SearchSortedPrimitiveArray approach). vortex-runend itself is left unchanged.

3. Integration with compression pipeline:

   • New BoolRunEndScheme in vortex-btrblocks for automatic bool array compression
   • Estimates compression ratio based on run count (profitable when average run length > 8), cascading the run ends child for further compression
   • Registered in the default compression scheme list

4. File format support:

   • RunEndBool registered in the default session; arrays serialize/deserialize correctly in the Vortex file format
   • Round-trip and compute-conformance covered by crate-level tests; test_run_heavy_bool_uses_runend in vortex-btrblocks asserts the compressor auto-selects the encoding

Design Notes

• Boolean runs strictly alternate, so run i has value value_at_index(i, start) where even indices equal start and odd indices equal !start
• The encoding preserves run structure through filtering and slicing operations
• Sparse filters (< 10% of runs kept) decode via per-index binary search; dense filters scan runs once and stay run-end encoded
• All compute operations respect optional validity arrays

[codspeed-hq]

Merging this PR will improve performance by 19.09%

⚠️ 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.

⚡ 4 improved benchmarks
❌ 1 regressed benchmark
✅ 1592 untouched benchmarks
⏩ 4 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	chunked_varbinview_into_canonical[(100, 100)]	272.2 µs	307.1 µs	-11.39%
⚡	Simulation	chunked_bool_canonical_into[(1000, 10)]	26.8 µs	16.4 µs	+63.47%
⚡	Simulation	chunked_varbinview_canonical_into[(1000, 10)]	191.4 µs	154.8 µs	+23.66%
⚡	Simulation	chunked_varbinview_into_canonical[(1000, 10)]	205.9 µs	169.8 µs	+21.26%
⚡	Simulation	eq_i64_constant	319.8 µs	290.1 µs	+10.25%

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 claude/runend-bool-compression-r148yw (8133d43) with develop (ee2cd67)}

Footnotes

1. 4 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. ↩

[github-actions]

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