Reduce per-byte overhead in VLQ integer decoding

[Dandandan]

Which issue does this PR close?

Closes #9580

Rationale

The current VLQ decoder calls get_aligned for each byte, which involves repeated offset calculations and bounds checks in the hot loop.

What changes are included in this PR?

Align to the byte boundary once, then iterate directly over the buffer slice, avoiding per-byte overhead from get_aligned.

Are there any user-facing changes?

No.

🤖 Generated with Claude Code

[Dandandan]

run benchmark arrow_reader_clickbench

[adriangbot]

🤖 Arrow criterion benchmark running (GKE) | trigger
Linux bench-c4093148017-469-769vg 6.12.55+ #1 SMP Sun Feb 1 08:59:41 UTC 2026 aarch64 GNU/Linux
Comparing pr/vlq-decoding (9098f72) to 88422cb (merge-base) diff
BENCH_NAME=arrow_reader_clickbench
BENCH_COMMAND=cargo bench --features=arrow,async,test_common,experimental,object_store --bench arrow_reader_clickbench
BENCH_FILTER=
Results will be posted here when complete

[adriangbot]

🤖 Arrow criterion benchmark completed (GKE) | trigger

Details

group                                             main                                   pr_vlq-decoding
-----                                             ----                                   ---------------
arrow_reader_clickbench/async/Q1                  1.00   1086.3±5.25µs        ? ?/sec    1.00   1084.3±5.54µs        ? ?/sec
arrow_reader_clickbench/async/Q10                 1.00      6.8±0.21ms        ? ?/sec    1.00      6.8±0.16ms        ? ?/sec
arrow_reader_clickbench/async/Q11                 1.00      7.8±0.19ms        ? ?/sec    1.00      7.8±0.14ms        ? ?/sec
arrow_reader_clickbench/async/Q12                 1.02     14.9±0.20ms        ? ?/sec    1.00     14.6±0.20ms        ? ?/sec
arrow_reader_clickbench/async/Q13                 1.03     17.6±0.35ms        ? ?/sec    1.00     17.1±0.28ms        ? ?/sec
arrow_reader_clickbench/async/Q14                 1.01     16.1±0.29ms        ? ?/sec    1.00     15.9±0.24ms        ? ?/sec
arrow_reader_clickbench/async/Q19                 1.01      3.2±0.07ms        ? ?/sec    1.00      3.1±0.04ms        ? ?/sec
arrow_reader_clickbench/async/Q20                 1.00     73.7±0.56ms        ? ?/sec    1.21    88.9±13.41ms        ? ?/sec
arrow_reader_clickbench/async/Q21                 1.02     82.1±0.63ms        ? ?/sec    1.00     80.4±0.25ms        ? ?/sec
arrow_reader_clickbench/async/Q22                 1.00    115.6±4.56ms        ? ?/sec    1.16   134.2±10.67ms        ? ?/sec
arrow_reader_clickbench/async/Q23                 1.04    250.7±3.83ms        ? ?/sec    1.00    240.5±2.93ms        ? ?/sec
arrow_reader_clickbench/async/Q24                 1.01     19.7±0.35ms        ? ?/sec    1.00     19.5±0.22ms        ? ?/sec
arrow_reader_clickbench/async/Q27                 1.03     59.2±0.49ms        ? ?/sec    1.00     57.2±0.24ms        ? ?/sec
arrow_reader_clickbench/async/Q28                 1.04     59.4±0.67ms        ? ?/sec    1.00     57.0±0.40ms        ? ?/sec
arrow_reader_clickbench/async/Q30                 1.01     18.7±0.18ms        ? ?/sec    1.00     18.5±0.11ms        ? ?/sec
arrow_reader_clickbench/async/Q36                 1.04     15.7±0.37ms        ? ?/sec    1.00     15.2±0.24ms        ? ?/sec
arrow_reader_clickbench/async/Q37                 1.00      5.5±0.07ms        ? ?/sec    1.00      5.5±0.08ms        ? ?/sec
arrow_reader_clickbench/async/Q38                 1.03     13.6±0.37ms        ? ?/sec    1.00     13.2±0.20ms        ? ?/sec
arrow_reader_clickbench/async/Q39                 1.05     25.2±0.57ms        ? ?/sec    1.00     24.0±0.20ms        ? ?/sec
arrow_reader_clickbench/async/Q40                 1.03      5.9±0.11ms        ? ?/sec    1.00      5.7±0.06ms        ? ?/sec
arrow_reader_clickbench/async/Q41                 1.02      5.1±0.05ms        ? ?/sec    1.00      5.0±0.03ms        ? ?/sec
arrow_reader_clickbench/async/Q42                 1.01      3.6±0.03ms        ? ?/sec    1.00      3.6±0.03ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q1     1.00   1067.8±4.36µs        ? ?/sec    1.01   1079.9±8.70µs        ? ?/sec
arrow_reader_clickbench/async_object_store/Q10    1.00      6.7±0.16ms        ? ?/sec    1.00      6.6±0.10ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q11    1.00      7.7±0.18ms        ? ?/sec    1.00      7.7±0.11ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q12    1.03     14.8±0.20ms        ? ?/sec    1.00     14.4±0.21ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q13    1.03     17.3±0.36ms        ? ?/sec    1.00     16.8±0.27ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q14    1.01     16.1±0.31ms        ? ?/sec    1.00     16.0±0.20ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q19    1.03      3.0±0.05ms        ? ?/sec    1.00      2.9±0.04ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q20    1.02     72.0±0.66ms        ? ?/sec    1.00     70.7±0.36ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q21    1.03     81.3±0.73ms        ? ?/sec    1.00     79.2±0.30ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q22    1.04     99.4±0.84ms        ? ?/sec    1.00     95.8±0.49ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q23    1.01    228.1±1.62ms        ? ?/sec    1.00    226.3±2.77ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q24    1.00     19.4±0.34ms        ? ?/sec    1.00     19.4±0.28ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q27    1.03     57.6±0.70ms        ? ?/sec    1.00     55.9±0.37ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q28    1.04     57.9±0.71ms        ? ?/sec    1.00     55.7±0.50ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q30    1.00     18.3±0.22ms        ? ?/sec    1.00     18.3±0.12ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q36    1.04     14.9±0.43ms        ? ?/sec    1.00     14.4±0.55ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q37    1.01      5.4±0.07ms        ? ?/sec    1.00      5.4±0.05ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q38    1.00     12.9±0.40ms        ? ?/sec    1.00     12.9±0.35ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q39    1.06     24.2±0.67ms        ? ?/sec    1.00     22.9±0.43ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q40    1.03      5.7±0.13ms        ? ?/sec    1.00      5.5±0.09ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q41    1.01      4.9±0.07ms        ? ?/sec    1.00      4.8±0.04ms        ? ?/sec
arrow_reader_clickbench/async_object_store/Q42    1.01      3.5±0.04ms        ? ?/sec    1.00      3.5±0.04ms        ? ?/sec
arrow_reader_clickbench/sync/Q1                   1.00    866.4±2.49µs        ? ?/sec    1.01    872.6±2.22µs        ? ?/sec
arrow_reader_clickbench/sync/Q10                  1.01      5.2±0.07ms        ? ?/sec    1.00      5.2±0.04ms        ? ?/sec
arrow_reader_clickbench/sync/Q11                  1.02      6.2±0.07ms        ? ?/sec    1.00      6.1±0.05ms        ? ?/sec
arrow_reader_clickbench/sync/Q12                  1.03     22.2±0.65ms        ? ?/sec    1.00     21.5±0.18ms        ? ?/sec
arrow_reader_clickbench/sync/Q13                  1.17     28.8±1.08ms        ? ?/sec    1.00     24.6±0.15ms        ? ?/sec
arrow_reader_clickbench/sync/Q14                  1.01     23.2±0.28ms        ? ?/sec    1.00     23.1±0.21ms        ? ?/sec
arrow_reader_clickbench/sync/Q19                  1.03      2.8±0.04ms        ? ?/sec    1.00      2.7±0.03ms        ? ?/sec
arrow_reader_clickbench/sync/Q20                  1.04    124.8±0.78ms        ? ?/sec    1.00    120.3±0.61ms        ? ?/sec
arrow_reader_clickbench/sync/Q21                  1.03     99.0±1.03ms        ? ?/sec    1.00     96.1±0.70ms        ? ?/sec
arrow_reader_clickbench/sync/Q22                  1.04    147.3±1.23ms        ? ?/sec    1.00    141.9±1.23ms        ? ?/sec
arrow_reader_clickbench/sync/Q23                  1.02    278.5±8.61ms        ? ?/sec    1.00   272.7±14.39ms        ? ?/sec
arrow_reader_clickbench/sync/Q24                  1.01     27.5±0.45ms        ? ?/sec    1.00     27.2±0.37ms        ? ?/sec
arrow_reader_clickbench/sync/Q27                  1.03    109.7±0.89ms        ? ?/sec    1.00    106.1±0.64ms        ? ?/sec
arrow_reader_clickbench/sync/Q28                  1.05    107.8±0.87ms        ? ?/sec    1.00    103.0±0.49ms        ? ?/sec
arrow_reader_clickbench/sync/Q30                  1.03     19.2±0.16ms        ? ?/sec    1.00     18.7±0.16ms        ? ?/sec
arrow_reader_clickbench/sync/Q36                  1.02     22.6±0.40ms        ? ?/sec    1.00     22.3±0.29ms        ? ?/sec
arrow_reader_clickbench/sync/Q37                  1.00      6.9±0.04ms        ? ?/sec    1.01      7.0±0.06ms        ? ?/sec
arrow_reader_clickbench/sync/Q38                  1.01     11.5±0.19ms        ? ?/sec    1.00     11.3±0.17ms        ? ?/sec
arrow_reader_clickbench/sync/Q39                  1.02     21.0±0.34ms        ? ?/sec    1.00     20.7±0.21ms        ? ?/sec
arrow_reader_clickbench/sync/Q40                  1.02      5.4±0.10ms        ? ?/sec    1.00      5.3±0.07ms        ? ?/sec
arrow_reader_clickbench/sync/Q41                  1.00      5.6±0.05ms        ? ?/sec    1.00      5.7±0.06ms        ? ?/sec
arrow_reader_clickbench/sync/Q42                  1.00      4.4±0.04ms        ? ?/sec    1.00      4.4±0.03ms        ? ?/sec

Resource Usage

base (merge-base)

Metric	Value
Wall time	783.1s
Peak memory	3.1 GiB
Avg memory	3.0 GiB
CPU user	705.5s
CPU sys	77.6s
Disk read	12.0 KiB
Disk write	1.3 GiB

branch

Metric	Value
Wall time	789.6s
Peak memory	3.2 GiB
Avg memory	3.1 GiB
CPU user	722.8s
CPU sys	66.8s
Disk read	0 B
Disk write	171.4 MiB