Title: Fix casting list array to fixed size list
State: closed

Fix casting list array to fixed size list.

This bug was introduced in [datasets-2.17.0](https://github.com/huggingface/datasets/releases/tag/2.17.0) by PR: https://github.com/huggingface/datasets/pull/6283/files#diff-1cb2b66aa9311d729cfd83013dad56cf5afcda35b39dfd0bfe9c3813a049eab0R1899
- #6283

Fix #7020.

Comments: The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_7021). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.<details>
<summary>Show benchmarks</summary>

PyArrow==8.0.0

<details>
<summary>Show updated benchmarks!</summary>

### Benchmark: benchmark_array_xd.json

| metric | read_batch_formatted_as_numpy after write_array2d | read_batch_formatted_as_numpy after write_flattened_sequence | read_batch_formatted_as_numpy after write_nested_sequence | read_batch_unformated after write_array2d | read_batch_unformated after write_flattened_sequence | read_batch_unformated after write_nested_sequence | read_col_formatted_as_numpy after write_array2d | read_col_formatted_as_numpy after write_flattened_sequence | read_col_formatted_as_numpy after write_nested_sequence | read_col_unformated after write_array2d | read_col_unformated after write_flattened_sequence | read_col_unformated after write_nested_sequence | read_formatted_as_numpy after write_array2d | read_formatted_as_numpy after write_flattened_sequence | read_formatted_as_numpy after write_nested_sequence | read_unformated after write_array2d | read_unformated after write_flattened_sequence | read_unformated after write_nested_sequence | write_array2d | write_flattened_sequence | write_nested_sequence |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.005126 / 0.011353 (-0.006227) | 0.003417 / 0.011008 (-0.007591) | 0.063274 / 0.038508 (0.024766) | 0.030896 / 0.023109 (0.007787) | 0.246661 / 0.275898 (-0.029237) | 0.275037 / 0.323480 (-0.048443) | 0.003243 / 0.007986 (-0.004742) | 0.003460 / 0.004328 (-0.000868) | 0.049665 / 0.004250 (0.045414) | 0.045826 / 0.037052 (0.008773) | 0.254360 / 0.258489 (-0.004129) | 0.294934 / 0.293841 (0.001094) | 0.029115 / 0.128546 (-0.099431) | 0.011908 / 0.075646 (-0.063738) | 0.207429 / 0.419271 (-0.211842) | 0.036371 / 0.043533 (-0.007162) | 0.249127 / 0.255139 (-0.006012) | 0.273982 / 0.283200 (-0.009218) | 0.019318 / 0.141683 (-0.122365) | 1.108985 / 1.452155 (-0.343169) | 1.147234 / 1.492716 (-0.345482) |

### Benchmark: benchmark_getitem\_100B.json

| metric | get_batch_of\_1024\_random_rows | get_batch_of\_1024\_rows | get_first_row | get_last_row |
|--------|---|---|---|---|
| new / old (diff) | 0.104830 / 0.018006 (0.086824) | 0.313453 / 0.000490 (0.312964) | 0.000213 / 0.000200 (0.000013) | 0.000043 / 0.000054 (-0.000012) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.019140 / 0.037411 (-0.018271) | 0.062160 / 0.014526 (0.047634) | 0.073537 / 0.176557 (-0.103020) | 0.119605 / 0.737135 (-0.617530) | 0.074707 / 0.296338 (-0.221632) |

### Benchmark: benchmark_iterating.json

| metric | read 5000 | read 50000 | read_batch 50000 10 | read_batch 50000 100 | read_batch 50000 1000 | read_formatted numpy 5000 | read_formatted pandas 5000 | read_formatted tensorflow 5000 | read_formatted torch 5000 | read_formatted_batch numpy 5000 10 | read_formatted_batch numpy 5000 1000 | shuffled read 5000 | shuffled read 50000 | shuffled read_batch 50000 10 | shuffled read_batch 50000 100 | shuffled read_batch 50000 1000 | shuffled read_formatted numpy 5000 | shuffled read_formatted_batch numpy 5000 10 | shuffled read_formatted_batch numpy 5000 1000 |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.282600 / 0.215209 (0.067391) | 2.805560 / 2.077655 (0.727906) | 1.471312 / 1.504120 (-0.032808) | 1.360920 / 1.541195 (-0.180275) | 1.361132 / 1.468490 (-0.107358) | 0.714791 / 4.584777 (-3.869986) | 2.405224 / 3.745712 (-1.340488) | 2.814498 / 5.269862 (-2.455363) | 1.896792 / 4.565676 (-2.668884) | 0.078138 / 0.424275 (-0.346137) | 0.005430 / 0.007607 (-0.002177) | 0.345529 / 0.226044 (0.119485) | 3.366205 / 2.268929 (1.097277) | 1.862820 / 55.444624 (-53.581805) | 1.555970 / 6.876477 (-5.320507) | 1.665102 / 2.142072 (-0.476970) | 0.798679 / 4.805227 (-4.006548) | 0.132601 / 6.500664 (-6.368064) | 0.041819 / 0.075469 (-0.033650) |

### Benchmark: benchmark_map_filter.json

| metric | filter | map fast-tokenizer batched | map identity | map identity batched | map no-op batched | map no-op batched numpy | map no-op batched pandas | map no-op batched pytorch | map no-op batched tensorflow |
|--------|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.972545 / 1.841788 (-0.869242) | 11.250626 / 8.074308 (3.176318) | 9.211127 / 10.191392 (-0.980265) | 0.130818 / 0.680424 (-0.549605) | 0.014123 / 0.534201 (-0.520078) | 0.298384 / 0.579283 (-0.280899) | 0.269736 / 0.434364 (-0.164628) | 0.341322 / 0.540337 (-0.199015) | 0.466915 / 1.386936 (-0.920021) |

</details>
PyArrow==latest

<details>
<summary>Show updated benchmarks!</summary>

### Benchmark: benchmark_array_xd.json

| metric | read_batch_formatted_as_numpy after write_array2d | read_batch_formatted_as_numpy after write_flattened_sequence | read_batch_formatted_as_numpy after write_nested_sequence | read_batch_unformated after write_array2d | read_batch_unformated after write_flattened_sequence | read_batch_unformated after write_nested_sequence | read_col_formatted_as_numpy after write_array2d | read_col_formatted_as_numpy after write_flattened_sequence | read_col_formatted_as_numpy after write_nested_sequence | read_col_unformated after write_array2d | read_col_unformated after write_flattened_sequence | read_col_unformated after write_nested_sequence | read_formatted_as_numpy after write_array2d | read_formatted_as_numpy after write_flattened_sequence | read_formatted_as_numpy after write_nested_sequence | read_unformated after write_array2d | read_unformated after write_flattened_sequence | read_unformated after write_nested_sequence | write_array2d | write_flattened_sequence | write_nested_sequence |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.005884 / 0.011353 (-0.005469) | 0.003983 / 0.011008 (-0.007025) | 0.050295 / 0.038508 (0.011787) | 0.033906 / 0.023109 (0.010797) | 0.271364 / 0.275898 (-0.004534) | 0.290652 / 0.323480 (-0.032828) | 0.004503 / 0.007986 (-0.003483) | 0.002946 / 0.004328 (-0.001382) | 0.049336 / 0.004250 (0.045086) | 0.040987 / 0.037052 (0.003935) | 0.283088 / 0.258489 (0.024599) | 0.313132 / 0.293841 (0.019291) | 0.032545 / 0.128546 (-0.096001) | 0.012622 / 0.075646 (-0.063024) | 0.060574 / 0.419271 (-0.358698) | 0.033625 / 0.043533 (-0.009908) | 0.266765 / 0.255139 (0.011626) | 0.286164 / 0.283200 (0.002964) | 0.018840 / 0.141683 (-0.122843) | 1.167874 / 1.452155 (-0.284281) | 1.170767 / 1.492716 (-0.321950) |

### Benchmark: benchmark_getitem\_100B.json

| metric | get_batch_of\_1024\_random_rows | get_batch_of\_1024\_rows | get_first_row | get_last_row |
|--------|---|---|---|---|
| new / old (diff) | 0.102266 / 0.018006 (0.084260) | 0.309530 / 0.000490 (0.309040) | 0.000210 / 0.000200 (0.000010) | 0.000043 / 0.000054 (-0.000011) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.023879 / 0.037411 (-0.013533) | 0.076837 / 0.014526 (0.062311) | 0.088718 / 0.176557 (-0.087839) | 0.129422 / 0.737135 (-0.607714) | 0.090051 / 0.296338 (-0.206287) |

### Benchmark: benchmark_iterating.json

| metric | read 5000 | read 50000 | read_batch 50000 10 | read_batch 50000 100 | read_batch 50000 1000 | read_formatted numpy 5000 | read_formatted pandas 5000 | read_formatted tensorflow 5000 | read_formatted torch 5000 | read_formatted_batch numpy 5000 10 | read_formatted_batch numpy 5000 1000 | shuffled read 5000 | shuffled read 50000 | shuffled read_batch 50000 10 | shuffled read_batch 50000 100 | shuffled read_batch 50000 1000 | shuffled read_formatted numpy 5000 | shuffled read_formatted_batch numpy 5000 10 | shuffled read_formatted_batch numpy 5000 1000 |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.287325 / 0.215209 (0.072116) | 2.844051 / 2.077655 (0.766397) | 1.552338 / 1.504120 (0.048218) | 1.422390 / 1.541195 (-0.118804) | 1.458580 / 1.468490 (-0.009910) | 0.712103 / 4.584777 (-3.872674) | 0.935116 / 3.745712 (-2.810596) | 2.891878 / 5.269862 (-2.377984) | 1.884683 / 4.565676 (-2.680994) | 0.077810 / 0.424275 (-0.346465) | 0.005087 / 0.007607 (-0.002520) | 0.337981 / 0.226044 (0.111937) | 3.346176 / 2.268929 (1.077248) | 1.892525 / 55.444624 (-53.552100) | 1.595472 / 6.876477 (-5.281004) | 1.595617 / 2.142072 (-0.546455) | 0.779581 / 4.805227 (-4.025647) | 0.131042 / 6.500664 (-6.369623) | 0.040665 / 0.075469 (-0.034804) |

### Benchmark: benchmark_map_filter.json

| metric | filter | map fast-tokenizer batched | map identity | map identity batched | map no-op batched | map no-op batched numpy | map no-op batched pandas | map no-op batched pytorch | map no-op batched tensorflow |
|--------|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 1.063560 / 1.841788 (-0.778227) | 12.030321 / 8.074308 (3.956013) | 10.213963 / 10.191392 (0.022571) | 0.142954 / 0.680424 (-0.537470) | 0.015700 / 0.534201 (-0.518501) | 0.311536 / 0.579283 (-0.267747) | 0.127064 / 0.434364 (-0.307300) | 0.351636 / 0.540337 (-0.188702) | 0.442281 / 1.386936 (-0.944655) |

</details>
</details>

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