[robert3005]

Add SparseScheme for FixedSizedList. Instead of compressing just the elements we attempt compressing whole lists using SparseArray

Readers need no changes, because Sparse already canonicalizes fixed-size lists.

On the data from #10417:

	Before	After
Mostly-null file (1 row in 20 valid)	25,296 B	9,056 B
Rewrite of both files	292,808 B	190,768 B

[codspeed]

Merging this PR will regress 2 benchmarks

⚠️ 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.

⚠️ 17 benchmarks spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

• compress_fsst[(500, 16, 8)]
• pcodec_compress_f64
• test_scan_filter[int_str_float]
• test_scan_filter[int_float]
• test_scan[int_str_float]
• decompress[u32, (1000, 256)]
• test_scan_filter[int_str]
• multipolygon_mixed_validity
• random_i128[0.01]
• test_scan[int_str]
• …and 7 more

ℹ️ 40 benchmarks have no flame graph

The flamegraph could not be generated because we failed to resolve the symbols in the profiling trace. This happens when we fail to harvest information about language frames.

• test_repeated_scan_scalar_at[int_str]
• test_repeated_scan[int]
• test_scan_filter[int]
• test_scan[int_float]
• test_scan_filter[int_str_float]
• test_repeated_scan_scalar_at[int_str_float]
• test_scan_filter[int_float]
• test_repeated_scan_scalar_at[int]
• test_repeated_scan_filter[int_str]
• test_scan_scalar_at[int_str_float]
• …and 30 more

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 2 improved benchmarks
❌ 2 regressed benchmarks
✅ 2404 untouched benchmarks
⏩ 12 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	WallTime	bitpack_blocked_compress_avx2	6.7 µs	7.6 µs	-11.5%
❌	Simulation	take[routing/grouped_chunks/primitive/nonnull/chunks=32/indices=1000]	385 µs	428.4 µs	-10.14%
⚡ ℹ️	Simulation	test_repeated_scan_scalar_at[int_str]	481.3 µs	406.6 µs	+18.38%
⚡	WallTime	starts_with_avx2[64, VarBin]	60.4 µs	54.2 µs	+11.48%

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 rk/compress-fsl-validity (24e77ed) with develop (61ff28d)}

Footnotes

1. 12 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. ↩