fix: correct DropByIndex handling of negative indices out of bounds#778
Merged
samber merged 1 commit intosamber:masterfrom Feb 22, 2026
Merged
fix: correct DropByIndex handling of negative indices out of bounds#778samber merged 1 commit intosamber:masterfrom
DropByIndex handling of negative indices out of bounds#778samber merged 1 commit intosamber:masterfrom
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+ Coverage 94.18% 94.19% +0.01%
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Lines 2872 2879 +7
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+ Hits 2705 2712 +7
Misses 151 151
Partials 16 16
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Fixed DropByIndex function for the case when a negative index exceeds
the slice size. This caused subsequent indices to have incorrect
offsets, leading to incorrect results.
Example of the bug:
DropByIndex([]int{0, 1, 2, 3, 4}, -100, 4)
returned []int{0, 1, 2, 4} instead of []int{0, 1, 2, 3}
Improvements:
- Removed map-based uniqueness check, now uses sorted iteration with O(1) memory
- Added copy of indexes to prevent mutation of input
- Fixed negative index handling logic
- Improved range check using uint for proper bounds validation
Performance:
- Time: -75.61% (geomean)
- Memory: -62.65% (geomean)
- Allocations: -43.67% (geomean)
Additional:
- Optimized Filter and FilterI in mutable/slice.go
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a6fc4c4
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DropByIndex handling of negative indices out of bounds
Contributor
Author
Full new benchmarks results │ old.txt │ new.txt │
│ sec/op │ sec/op vs base │
DropByIndex/size_10/indexes_1/strings-4 165.8n ± 23% 145.2n ± 42% ~ (p=0.469 n=10)
DropByIndex/size_10/indexes_1/ints-4 110.90n ± 25% 78.27n ± 34% -29.42% (p=0.011 n=10)
DropByIndex/size_10/indexes_1/heavy-4 3.668µ ± 32% 3.256µ ± 30% ~ (p=0.684 n=10)
DropByIndex/size_10/indexes_4/strings-4 233.2n ± 26% 102.5n ± 15% -56.06% (p=0.000 n=10)
DropByIndex/size_10/indexes_4/ints-4 214.20n ± 22% 71.70n ± 66% -66.53% (p=0.000 n=10)
DropByIndex/size_10/indexes_4/heavy-4 3.535µ ± 19% 2.003µ ± 26% -43.34% (p=0.000 n=10)
DropByIndex/size_10/indexes_10/strings-4 674.9n ± 24% 115.4n ± 35% -82.90% (p=0.000 n=10)
DropByIndex/size_10/indexes_10/ints-4 603.9n ± 128% 108.5n ± 18% -82.03% (p=0.000 n=10)
DropByIndex/size_10/indexes_10/heavy-4 4632.5n ± 24% 125.1n ± 20% -97.30% (p=0.000 n=10)
DropByIndex/size_100/indexes_1/strings-4 317.8n ± 118% 259.0n ± 280% ~ (p=0.143 n=10)
DropByIndex/size_100/indexes_1/ints-4 220.5n ± 38% 216.8n ± 44% ~ (p=0.684 n=10)
DropByIndex/size_100/indexes_1/heavy-4 80.47µ ± 45% 26.27µ ± 27% -67.36% (p=0.000 n=10)
DropByIndex/size_100/indexes_4/strings-4 1309.5n ± 37% 270.2n ± 55% -79.37% (p=0.000 n=10)
DropByIndex/size_100/indexes_4/ints-4 669.9n ± 39% 136.0n ± 17% -79.70% (p=0.000 n=10)
DropByIndex/size_100/indexes_4/heavy-4 25.28µ ± 25% 24.44µ ± 18% ~ (p=0.631 n=10)
DropByIndex/size_100/indexes_100/strings-4 8216.0n ± 99% 850.8n ± 18% -89.64% (p=0.000 n=10)
DropByIndex/size_100/indexes_100/ints-4 6430.5n ± 15% 738.8n ± 29% -88.51% (p=0.000 n=10)
DropByIndex/size_100/indexes_100/heavy-4 83162.5n ± 6% 739.6n ± 19% -99.11% (p=0.000 n=10)
DropByIndex/size_1000/indexes_1/strings-4 10.747µ ± 41% 6.312µ ± 38% -41.27% (p=0.007 n=10)
DropByIndex/size_1000/indexes_1/ints-4 3.490µ ± 27% 2.982µ ± 30% ~ (p=0.165 n=10)
DropByIndex/size_1000/indexes_1/heavy-4 175.1µ ± 25% 190.1µ ± 31% ~ (p=0.315 n=10)
DropByIndex/size_1000/indexes_4/strings-4 11.742µ ± 40% 6.286µ ± 37% -46.46% (p=0.001 n=10)
DropByIndex/size_1000/indexes_4/ints-4 3.292µ ± 35% 3.311µ ± 21% ~ (p=1.000 n=10)
DropByIndex/size_1000/indexes_4/heavy-4 279.6µ ± 20% 240.0µ ± 20% ~ (p=0.190 n=10)
DropByIndex/size_1000/indexes_1000/strings-4 338.14µ ± 14% 10.84µ ± 23% -96.80% (p=0.000 n=10)
DropByIndex/size_1000/indexes_1000/ints-4 83.615µ ± 6% 8.361µ ± 19% -90.00% (p=0.000 n=10)
DropByIndex/size_1000/indexes_1000/heavy-4 10682.897µ ± 7% 8.888µ ± 29% -99.92% (p=0.000 n=10)
geomean 5.707µ 1.392µ -75.61%
│ old.txt │ new.txt │
│ B/op │ B/op vs base │
DropByIndex/size_10/indexes_1/strings-4 160.0 ± 0% 144.0 ± 0% -10.00% (p=0.000 n=10)
DropByIndex/size_10/indexes_1/ints-4 80.00 ± 0% 80.00 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_10/indexes_1/heavy-4 8.000Ki ± 0% 8.000Ki ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_10/indexes_4/strings-4 160.00 ± 0% 96.00 ± 0% -40.00% (p=0.000 n=10)
DropByIndex/size_10/indexes_4/ints-4 80.00 ± 0% 48.00 ± 0% -40.00% (p=0.000 n=10)
DropByIndex/size_10/indexes_4/heavy-4 8.000Ki ± 0% 4.750Ki ± 0% -40.62% (p=0.000 n=10)
DropByIndex/size_10/indexes_10/strings-4 568.00 ± 0% 80.00 ± 0% -85.92% (p=0.000 n=10)
DropByIndex/size_10/indexes_10/ints-4 488.00 ± 0% 80.00 ± 0% -83.61% (p=0.000 n=10)
DropByIndex/size_10/indexes_10/heavy-4 8600.00 ± 0% 80.00 ± 0% -99.07% (p=0.000 n=10)
DropByIndex/size_100/indexes_1/strings-4 1.750Ki ± 0% 1.750Ki ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_100/indexes_1/ints-4 896.0 ± 0% 896.0 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_100/indexes_1/heavy-4 80.00Ki ± 0% 80.00Ki ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_100/indexes_4/strings-4 1.750Ki ± 0% 1.750Ki ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_100/indexes_4/ints-4 896.0 ± 0% 768.0 ± 0% -14.29% (p=0.000 n=10)
DropByIndex/size_100/indexes_4/heavy-4 80.00Ki ± 0% 80.00Ki ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_100/indexes_100/strings-4 5032.0 ± 0% 896.0 ± 0% -82.19% (p=0.000 n=10)
DropByIndex/size_100/indexes_100/ints-4 4136.0 ± 0% 896.0 ± 0% -78.34% (p=0.000 n=10)
DropByIndex/size_100/indexes_100/heavy-4 85160.0 ± 0% 896.0 ± 0% -98.95% (p=0.000 n=10)
DropByIndex/size_1000/indexes_1/strings-4 16.00Ki ± 0% 16.00Ki ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_1000/indexes_1/ints-4 8.000Ki ± 0% 8.000Ki ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_1000/indexes_1/heavy-4 784.0Ki ± 0% 784.0Ki ± 0% ~ (p=0.995 n=10)
DropByIndex/size_1000/indexes_4/strings-4 16.00Ki ± 0% 16.00Ki ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_1000/indexes_4/ints-4 8.000Ki ± 0% 8.000Ki ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_1000/indexes_4/heavy-4 784.0Ki ± 0% 784.0Ki ± 0% -0.00% (p=0.017 n=10)
DropByIndex/size_1000/indexes_1000/strings-4 60.078Ki ± 0% 8.000Ki ± 0% -86.68% (p=0.000 n=10)
DropByIndex/size_1000/indexes_1000/ints-4 52.078Ki ± 0% 8.000Ki ± 0% -84.64% (p=0.000 n=10)
DropByIndex/size_1000/indexes_1000/heavy-4 828.079Ki ± 0% 8.000Ki ± 0% -99.03% (p=0.000 n=10)
geomean 6.605Ki 2.467Ki -62.65%
¹ all samples are equal
│ old.txt │ new.txt │
│ allocs/op │ allocs/op vs base │
DropByIndex/size_10/indexes_1/strings-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_10/indexes_1/ints-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_10/indexes_1/heavy-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_10/indexes_4/strings-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_10/indexes_4/ints-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_10/indexes_4/heavy-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_10/indexes_10/strings-4 5.000 ± 0% 1.000 ± 0% -80.00% (p=0.000 n=10)
DropByIndex/size_10/indexes_10/ints-4 5.000 ± 0% 1.000 ± 0% -80.00% (p=0.000 n=10)
DropByIndex/size_10/indexes_10/heavy-4 5.000 ± 0% 1.000 ± 0% -80.00% (p=0.000 n=10)
DropByIndex/size_100/indexes_1/strings-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_100/indexes_1/ints-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_100/indexes_1/heavy-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_100/indexes_4/strings-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_100/indexes_4/ints-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_100/indexes_4/heavy-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_100/indexes_100/strings-4 5.000 ± 0% 1.000 ± 0% -80.00% (p=0.000 n=10)
DropByIndex/size_100/indexes_100/ints-4 5.000 ± 0% 1.000 ± 0% -80.00% (p=0.000 n=10)
DropByIndex/size_100/indexes_100/heavy-4 5.000 ± 0% 1.000 ± 0% -80.00% (p=0.000 n=10)
DropByIndex/size_1000/indexes_1/strings-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_1000/indexes_1/ints-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_1000/indexes_1/heavy-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_1000/indexes_4/strings-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_1000/indexes_4/ints-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_1000/indexes_4/heavy-4 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
DropByIndex/size_1000/indexes_1000/strings-4 7.000 ± 0% 1.000 ± 0% -85.71% (p=0.000 n=10)
DropByIndex/size_1000/indexes_1000/ints-4 7.000 ± 0% 1.000 ± 0% -85.71% (p=0.000 n=10)
DropByIndex/size_1000/indexes_1000/heavy-4 7.000 ± 0% 1.000 ± 0% -85.71% (p=0.000 n=10)
geomean 1.775 1.000 -43.67% |
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Fixed DropByIndex function for the case when a negative index exceeds
the slice size. This caused subsequent indices to have incorrect
offsets, leading to incorrect results.
Example of the bug:
DropByIndex([]int{0, 1, 2, 3, 4}, -100, 4)returned
[]int{0, 1, 2, 4}instead of[]int{0, 1, 2, 3}Improvements:
Performance:
Additional: