[connortsui20]

Summary

Fixes #10623.

Dict::fill_null converted the index of the matching dictionary value into the codes type with an unchecked as cast. A dictionary can hold more values than its codes type can index, so an unreferenced fill value could truncate to the wrong code (with u8 codes, filling with value 300 returned value 44) or panic for signed codes.

Changes

The kernel now checks the index against the range of the codes type. When the index does not fit, the kernel declines and the generic fill_null path fills the decoded array, which is slower but correct. Non-nullable codes need no fill code, so they keep the fast path. The new tests cover u8 and i8 codes at and past their maximum, and non-nullable codes over nullable values. The three cases past the maximum fail without the fix.

The Narrow work (#10733) depends on this fix, because a rule there makes narrow dictionary codes common.

🤖 Generated with Claude Code

[codspeed]

Merging this PR will degrade performance by 4.18%

4 warnings, 1 note

⚠️ Walltime results may be unreliable

Some benchmarks used the Walltime instrument outside CodSpeed Macro Runners, which can make the results inconsistent.

Learn more about Macro Runners

See affected benchmarks

⚠️ Unable to measure the execution of 2 benchmarks

These benchmarks measured no execution time, so their results are not comparable and count as unchanged. This usually happens when the compiler removes the code under test.

Prevent compiler optimizations

See affected benchmarks

⚠️ 22 benchmarks are dominated by system calls

System calls cannot be simulated consistently and are left out of the measure. The reported value understates the real cost. Switch to the Walltime instrument to measure them.

Learn more about system calls

See affected benchmarks

⚠️ Base and head ran on different runner types

Some benchmarks with significant performance changes were compared across different runner types, so the changes might not come from the code. Run base and head on the same runner type, or use CodSpeed Macro Runners for more stable results.

Learn more about Macro Runners

Open the report in CodSpeed to investigate

ℹ️ 40 benchmarks have no flamegraph

The flamegraph wasn't generated: the symbols of the profiling trace could not be resolved, because no information about the language frames was collected.

See affected benchmarks

⚡ 3 improved benchmarks
❌ 11 regressed benchmarks
✅ 2394 untouched benchmarks
⏩ 12 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	CPU Simulation	test_scan_filter_to_arrow_array[int_float]	3.5 ms	4.1 ms	-13.59%
❌	CPU Simulation	filter_powerlaw_by_mostly_false[250000]	138.6 µs	159.1 µs	-12.88%
❌	Walltime	bitpack_blocked_compress_avx2	6.7 µs	7.6 µs	-11.75%
❌	CPU Simulation	filter_random_by_mostly_false[250000]	163.2 µs	183.5 µs	-11.08%
❌	CPU Simulation	test_repeated_scan_filter[int_float]	3.4 ms	3.9 ms	-10.87%
❌	CPU Simulation	density_sweep_dense_runs[0.001]	53.6 µs	59.9 µs	-10.59%
❌	CPU Simulation	filter_powerlaw_by_power_law[250000]	166.1 µs	185.2 µs	-10.35%
❌	CPU Simulation	test_repeated_scan_filter[int]	2.4 ms	2.7 ms	-10.33%
❌	CPU Simulation	test_scan_filter_to_arrow_array[int]	2.5 ms	2.8 ms	-10.26%
❌	CPU Simulation	filter_random_by_power_law[250000]	166.1 µs	185.1 µs	-10.26%
❌	CPU Simulation	filter_powerlaw_by_random[250000]	153.7 µs	170.9 µs	-10.07%
⚡	CPU Simulation	bench_compare_primitive[(10000, 32)]	97 µs	71.8 µs	+35.22%
⚡	CPU Simulation	chunked_dict_primitive_canonical_into[f64, (1000, 1000, 10)]	191.7 µs	151.5 µs	+26.55%
⚡	Walltime	starts_with_avx2[8, VarBin]	46.9 µs	40 µs	+17.3%

Tip

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

---

_{Comparing ct/dict-fill-code (5602cd0) with develop (3974ee0)}

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. ↩

[connortsui20]

should we widen instead of just giving up here?