helmo/github-issues huggingface dataset:
Error of writing with different schema, due to nonpreservation of nullability
State: closed | Author: richarddwang (CONTRIBUTOR)

## 1. Case
```
dataset.map(
  batched=True,
  disable_nullable=True,
)
```
will get the following error at here https://github.com/huggingface/datasets/blob/c9967f55626931f8059dc416526c791444cdfdf7/src/datasets/arrow_writer.py#L516

`pyarrow.lib.ArrowInvalid: Tried to write record batch with different schema`

## 2. Debugging
### 2.1 tracing
During `_map_single`, the following are called
https://github.com/huggingface/datasets/blob/c9967f55626931f8059dc416526c791444cdfdf7/src/datasets/arrow_dataset.py#L2523
https://github.com/huggingface/datasets/blob/c9967f55626931f8059dc416526c791444cdfdf7/src/datasets/arrow_writer.py#L511
### 2.2. Observation
The problem is, even after `table_cast`, `pa_table.schema != self._schema`
`pa_table.schema` (before/after `table_cast`)
```
input_ids: list<item: int32>
  child 0, item: int32
```
`self._schema`
```
input_ids: list<item: int32> not null
  child 0, item: int32
```
### 2.3. Reason
https://github.com/huggingface/datasets/blob/c9967f55626931f8059dc416526c791444cdfdf7/src/datasets/table.py#L1121
Here we lose nullability stored in `schema` because it seems that `Features` is always nullable and don't store nullability.
https://github.com/huggingface/datasets/blob/c9967f55626931f8059dc416526c791444cdfdf7/src/datasets/table.py#L1103
So, casting to schema from such `Features` loses nullability, and eventually causes error of writing with different schema

## 3. Solution
1. Let `Features` stores nullability.
2. Directly cast table with original schema but not schema from converted `Features`. (this PR)
3. Don't `cast_table` when `write_table`

Comments: Hi ! Thanks for reporting, indeed `disable_nullable` doesn't seem to be supported in this case. Maybe at one point we can have `disable_nullable` as a parameter of certain feature types
Reddit dataset card additions
State: closed | Author: anna-kay (CONTRIBUTOR)

The changes proposed are based on the "TL;DR: Mining Reddit to Learn Automatic Summarization" paper & https://zenodo.org/record/1043504#.YhaKHpbQC38
It is a Reddit dataset indeed, but the name given to the dataset by the authors is Webis-TLDR-17 (corpus), so perhaps it should be modified as well. 
The task at which the dataset is aimed is abstractive summarization.


Comments: Hello! I added the tags and created a PR. Just to note, regarding the paperswithcode_id tag, that currently has the value "reddit"; the dataset described as reddit in paperswithcode is https://paperswithcode.com/dataset/reddit and it isn't the Webis-tldr-17. I could not find Webis-tldr-17 in paperswithcode neither in the Summarization category nor using the keywords reddit, webis, & tldr. I didn't change this tag.
Not be able to download dataset - "Newsroom"
State: closed | Author: Darshan2104 (NONE)
Labels: name: dataset bug

Hello,

I tried to download the **newsroom** dataset but it didn't work out for me. it said me to **download it manually**!

For manually, Link is also didn't work! It is sawing some ad or something!

If anybody has solved this issue please help me out or if somebody has this dataset please share your google drive link, it would be a great help!

Thanks
Darshan Tank

Comments: Hi @Darshan2104, thanks for reporting.

Please note that at Hugging Face we do not host the data of this dataset, but just a loading script pointing to the host of the data owners.

Apparently the data owners changed their data host server. After googling it, I found their new website at: https://lil.nlp.cornell.edu/newsroom/index.html
- Download page: https://lil.nlp.cornell.edu/newsroom/download/index.html

I'm fixing the link in our Datasets library.

@albertvillanova Thanks for the solution and link you made my day!
Start removing canonical datasets logic
State: closed | Author: lhoestq (MEMBER)

I updated the source code and the documentation to start removing the "canonical datasets" logic.

Indeed this makes the documentation confusing and we don't want this distinction anymore in the future. Ideally users should share their datasets on the Hub directly.

### Changes

- the documentation about dataset loading mentions the datasets on the Hub (no difference between canonical and community, since they all have their own repository now)
- the documentation about adding a dataset doesn't explain the technical differences between canonical and community anymore, and only presents how to add a community dataset. There is still a small section at the bottom that mentions the datasets that are still on GitHub and redirects to the `ADD_NEW_DATASET.md` guide on GitHub about how to contribute a dataset to the `datasets` library
- the code source doesn't mention "canonical" anymore anywhere. There is still a `GitHubDatasetModuleFactory` class that is left, but I updated the docstring to say that it will be eventually removed in favor of the `HubDatasetModuleFactory` classes that already exist

Would love to have your feedbacks on this !

cc @julien-c @thomwolf @SBrandeis 

Comments: I'm not sure if the documentation explains why the dataset identifiers might have a namespace or not (the user/org): 'glue' vs 'severo/glue'. Do you think we should explain it, and relate it to the GitHub/Hub distinction?

> I'm not sure if the documentation explains why the dataset identifiers might have a namespace or not (the user/org): 'glue' vs 'severo/glue'. Do you think we should explain it, and relate it to the GitHub/Hub distinction?

I added an explanation, let me know if it sounds good to you:

```
Datasets used to be hosted on our GitHub repository, but all datasets have now been migrated to the Hugging Face Hub.
The legacy GitHub datasets were added originally on our GitHub repository and therefore don't have a namespace: "squad", "glue", etc. unlike the other datasets that are named "username/dataset_name" or "org/dataset_name".
```


Thanks for the feedbacks ! Merging this now - if you have some comments I can take care of them in a subsequent PR

I'll also take care of resolving the conflicts with https://github.com/huggingface/datasets/pull/3690
Allow download only some files from the Wikipedia dataset
State: open | Author: jvanz (NONE)
Labels: name: enhancement

**Is your feature request related to a problem? Please describe.**
The Wikipedia dataset can be really big. This is a problem if you want to use it locally in a laptop with the Apache Beam `DirectRunner`. Even if your laptop have a considerable amount of memory (e.g. 32gb).


**Describe the solution you'd like**
I would like to use the `data_files` argument in the `load_dataset` function to define which file in the wikipedia dataset I would like to download. Thus, I can work with the dataset in a smaller machine using the Apache Beam `DirectRunner`.

**Describe alternatives you've considered**
I've tried to use the `simple` Wikipedia dataset. But it's in English and I would like to use Portuguese texts in my model. 


Comments: Hi @jvanz, thank you for your proposal.

In fact, we are aware that it is very common the problem you mention. Because of that, we are currently working in implementing a new version of wikipedia on the Hub, with all data preprocessed (no need to use Apache Beam), from where you will be able to use `data_files` to load only a specific subset of the data files.

See:
- #3401
Update gigaword card and info
State: closed | Author: mariosasko (COLLABORATOR)

Reported on the forum: https://discuss.huggingface.co/t/error-loading-dataset/14999

Comments: I think it actually comes from an issue here:

https://github.com/huggingface/datasets/blob/810b12f763f5cf02f2e43565b8890d278b7398cd/src/datasets/utils/file_utils.py#L575-L579

and 

https://github.com/huggingface/datasets/blob/810b12f763f5cf02f2e43565b8890d278b7398cd/src/datasets/utils/streaming_download_manager.py#L386-L389

This code doesn't seem to work anymore. This can probably be fixed with

```python
if url.startswith("https://drive.google.com/"): 
    url += "&confirm=t"
    cookies = response.cookies 
```

because Google Drive doesn't return the `download_warning` cookie anymore.

Actually it seems that is has been fixed already in https://github.com/huggingface/datasets/pull/3787 :)

I think it should have fixed the gigaword dataset loading

@lhoestq The linked PR indeed fixes the issue. This PR is still worth merging IMO to update `gigaword`'s card.
DuplicatedKeysError on msr_sqa dataset
State: closed | Author: kolk (NONE)

### Describe the bug
Failure to generate dataset msr_sqa because of duplicate keys.

### Steps to reproduce the bug
```
from datasets import load_dataset
load_dataset("msr_sqa")
```
### Expected results
The examples keys should be unique.

**Actual results**
```
>>> load_dataset("msr_sqa")
Downloading:
6.72k/? [00:00<00:00, 148kB/s]
Downloading:
2.93k/? [00:00<00:00, 53.8kB/s]
Using custom data configuration default
Downloading and preparing dataset msr_sqa/default (download: 4.57 MiB, generated: 26.25 MiB, post-processed: Unknown size, total: 30.83 MiB) to /root/.cache/huggingface/datasets/msr_sqa/default/0.0.0/70b2a497bd3cc8fc960a3557d2bad1eac5edde824505e15c9c8ebe4c260fd4d1...
Downloading: 100%
4.80M/4.80M [00:00<00:00, 7.49MB/s]
---------------------------------------------------------------------------
DuplicatedKeysError                       Traceback (most recent call last)
[/usr/local/lib/python3.7/dist-packages/datasets/builder.py](https://localhost:8080/#) in _prepare_split(self, split_generator)
   1080                     example = self.info.features.encode_example(record)
-> 1081                     writer.write(example, key)
   1082             finally:

8 frames
DuplicatedKeysError: FAILURE TO GENERATE DATASET !
Found duplicate Key: nt-639
Keys should be unique and deterministic in nature

During handling of the above exception, another exception occurred:

DuplicatedKeysError                       Traceback (most recent call last)
[/usr/local/lib/python3.7/dist-packages/datasets/arrow_writer.py](https://localhost:8080/#) in check_duplicate_keys(self)
    449         for hash, key in self.hkey_record:
    450             if hash in tmp_record:
--> 451                 raise DuplicatedKeysError(key)
    452             else:
    453                 tmp_record.add(hash)

DuplicatedKeysError: FAILURE TO GENERATE DATASET !
Found duplicate Key: nt-639
Keys should be unique and deterministic in nature
```

### Environment info
datasets version: 1.18.3
Platform: Google colab notebook
Python version: 3.7
PyArrow version: 6.0.1


Comments: Thanks for reporting, @kolk.

We are fixing it.
`dataset = dataset.map()` causes faiss index lost
State: open | Author: Oaklight (NONE)
Labels: name: bug

## Describe the bug
assigning the resulted dataset to original dataset causes lost of the faiss index

## Steps to reproduce the bug
`my_dataset` is a regular loaded dataset. It's a part of a customed dataset structure
```python
self.dataset.add_faiss_index('embeddings')
self.dataset.list_indexes()
# ['embeddings']

dataset2 = my_dataset.map(
    lambda x: self._get_nearest_examples_batch(x['text']), batch=True
)

# the unexpected result:
dataset2.list_indexes()
# []

self.dataset.list_indexes()
# ['embeddings']
```

in case something wrong with my `_get_nearest_examples_batch()`, it's like this
```python
def _get_nearest_examples_batch(self, examples, k=5):
    queries = embed(examples)
    scores_batch, retrievals_batch = self.dataset.get_nearest_examples_batch(self.faiss_column, queries, k)
    return {
        'neighbors': [batch['text'] for batch in retrievals_batch],
        'scores': scores_batch
    }
```

## Expected results
`map` shouldn't drop the indexes, in another word, indexes should be carried to the generated dataset

## Actual results
map drops the indexes

## Environment info
<!-- You can run the command `datasets-cli env` and copy-and-paste its output below. -->
- `datasets` version: 1.18.3
- Platform: Ubuntu 20.04.3 LTS
- Python version: 3.8.12
- PyArrow version: 7.0.0


Comments: Hi ! Indeed `map` is dropping the index right now, because one can create a dataset with more or fewer rows using `map` (and therefore the index might not be relevant anymore)

I guess we could check the resulting dataset length, and if the user hasn't changed the dataset size we could keep the index, what do you think ?

doing `.add_column("x",x_data)` also removes the index. the new column might be irrelevant to the index so I don't think it should drop. 

Minimal example

```python
from datasets import load_dataset
import numpy as np

data=load_dataset("ceyda/cats_vs_dogs_sample") #just a test dataset
data=data["train"]
embd_data=data.map(lambda x: {"emb":np.random.uniform(-1,0,50).astype(np.float32)})
embd_data.add_faiss_index(column="emb")
print(embd_data.list_indexes())
embd_data=embd_data.add_column("x",[0]*data.num_rows)
print(embd_data.list_indexes())
```

I agree `add_column` shouldn't drop the index indeed ! Is it something you'd like to contribute ? I think it's just a matter of copying the `self._indexes` dictionary to the output dataset
`Dataset.class_encode` should support custom class names
State: closed | Author: Dref360 (CONTRIBUTOR)
Labels: name: enhancement

I can make a PR, just wanted approval before starting.

**Is your feature request related to a problem? Please describe.**

It is often the case that classes are not ordered in alphabetical order. Current `class_encode_column` sort the classes before indexing.
https://github.com/huggingface/datasets/blob/master/src/datasets/arrow_dataset.py#L1235

**Describe the solution you'd like**
I would like to add a **optional** parameter `class_names` to `class_encode_column` that would  be used for the mapping instead of sorting the unique values.

**Describe alternatives you've considered**

One can use map instead. I find it harder to read.
```python
CLASS_NAMES = ['apple', 'orange', 'potato']
ds = ds.map(lambda item: CLASS_NAMES.index(item[label_column]))

# Proposition
ds = ds.class_encode_column(label_column, CLASS_NAMES)
```

**Additional context**

I can make the PR if this feature is accepted.


Comments: Hi @Dref360, thanks a lot for your proposal.

It totally makes sense to have more flexibility when class encoding, I agree.

You could even further customize the class encoding by passing an instance of `ClassLabel` itself (instead of replicating `ClassLabel` instantiation arguments as `Dataset.class_encode_column` arguments).

And the latter made me think of `Dataset.cast_column`...

Maybe better to have some others' opinions @lhoestq @mariosasko 

Hi @Dref360! You can use [`Dataset.align_labels_with_mapping`](https://huggingface.co/docs/datasets/master/package_reference/main_classes.html#datasets.Dataset.align_labels_with_mapping) after `Dataset.class_encode_column` to assign a different mapping of labels to ids.

@albertvillanova I'd like to avoid adding more complexity to the API where it's not (absolutely) needed, so I don't think introducing a new param in `Dataset.class_encode_column` is a good idea.



I wasn't aware that it existed thank you for the link.

Closing then!
Know your data for HF hub 
State: closed | Author: Muhtasham (NONE)
Labels: name: enhancement

**Is your feature request related to a problem? Please describe.**
Would be great to see be able to understand datasets with the goal of improving data quality, and helping mitigate fairness and bias issues.

**Describe the solution you'd like**
Something like https://knowyourdata.withgoogle.com/ for HF hub

Comments: Hi @Muhtasham you should take a look at https://huggingface.co/blog/data-measurements-tool and accompanying demo app at https://huggingface.co/spaces/huggingface/data-measurements-tool

We would be interested in your feedback. cc @meg-huggingface @sashavor @yjernite
Unable to view the Gradio flagged call back dataset
State: closed | Author: kingabzpro (NONE)
Labels: name: dataset-viewer

## Dataset viewer issue for '*savtadepth-flags*'

**Link:** *[savtadepth-flags](https://huggingface.co/datasets/kingabzpro/savtadepth-flags)*

*with the Gradio 2.8.1 the dataset viers stopped working. I tried to add values manually but its not working. The dataset is also not showing the link with the app https://huggingface.co/spaces/kingabzpro/savtadepth.*

Am I the one who added this dataset ? Yes


Comments: Hi @kingabzpro.

I think you need to create a loading script that creates the dataset from the CSV file and the image paths.

As example, you could have a look at the Food-101 dataset: https://huggingface.co/datasets/food101
- Loading script: https://huggingface.co/datasets/food101/blob/main/food101.py

Once the loading script is created, the viewer will show a previsualization of your dataset. 

@albertvillanova I don't think this is the issue. I have created another dataset with similar files and format and it works. https://huggingface.co/datasets/kingabzpro/savtadepth-flags-V2

Yes, you are right, that was not the issue.

Just take into account that sometimes the viewer can take some time until it shows the preview of the dataset.
After some time, yours is finally properly shown: https://huggingface.co/datasets/kingabzpro/savtadepth-flags

The problem was resolved by deleted the dataset and creating new one with similar name and then clicking on flag button.

I think if you make manual changes to dataset the whole system breaks.
Rename GenerateMode to DownloadMode
State: closed | Author: albertvillanova (MEMBER)

This PR:
- Renames `GenerateMode` to `DownloadMode`
- Implements `DeprecatedEnum`
- Deprecates `GenerateMode`

Close #769.

Comments: Thanks! Used here: https://github.com/huggingface/datasets-preview-backend/blob/main/src/datasets_preview_backend/models/dataset.py#L26 :)
head_qa file missing
State: closed | Author: severo (COLLABORATOR)
Labels: name: bug

## Describe the bug

A file for the `head_qa` dataset is missing (https://drive.google.com/u/0/uc?export=download&id=1a_95N5zQQoUCq8IBNVZgziHbeM-QxG2t/HEAD_EN/train_HEAD_EN.json)

## Steps to reproduce the bug
```python
>>> from datasets import load_dataset
>>> load_dataset("head_qa", name="en")
```

## Expected results

The dataset should be loaded

## Actual results

```
Downloading and preparing dataset head_qa/en (download: 75.69 MiB, generated: 2.69 MiB, post-processed: Unknown size, total: 78.38 MiB) to /home/slesage/.cache/huggingface/datasets/head_qa/en/1.1.0/583ab408e8baf54aab378c93715fadc4d8aa51b393e27c3484a877e2ac0278e9...
Downloading data: 2.21kB [00:00, 2.05MB/s]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/slesage/hf/datasets-preview-backend/.venv/lib/python3.9/site-packages/datasets/load.py", line 1729, in load_dataset
    builder_instance.download_and_prepare(
  File "/home/slesage/hf/datasets-preview-backend/.venv/lib/python3.9/site-packages/datasets/builder.py", line 594, in download_and_prepare
    self._download_and_prepare(
  File "/home/slesage/hf/datasets-preview-backend/.venv/lib/python3.9/site-packages/datasets/builder.py", line 665, in _download_and_prepare
    verify_checksums(
  File "/home/slesage/hf/datasets-preview-backend/.venv/lib/python3.9/site-packages/datasets/utils/info_utils.py", line 40, in verify_checksums
    raise NonMatchingChecksumError(error_msg + str(bad_urls))
datasets.utils.info_utils.NonMatchingChecksumError: Checksums didn't match for dataset source files:
['https://drive.google.com/u/0/uc?export=download&id=1a_95N5zQQoUCq8IBNVZgziHbeM-QxG2t']
```

## Environment info
- `datasets` version: 1.18.4.dev0
- Platform: Linux-5.11.0-1028-aws-x86_64-with-glibc2.31
- Python version: 3.9.6
- PyArrow version: 6.0.1


Comments: We usually find issues with files hosted at Google Drive...

In this case we download the Google Drive Virus scan warning instead of the data file.

Fixed: https://huggingface.co/datasets/head_qa/viewer/en/train. Thanks

<img width="1551" alt="Capture d’écran 2022-02-28 à 15 29 04" src="https://user-images.githubusercontent.com/1676121/156000224-fd3f62c6-8b54-4df1-8911-bdcb0bac3f1a.png">
Add perplexity to metrics
State: closed | Author: emibaylor (CONTRIBUTOR)

Adding perplexity metric

This code differs from the code in [this](https://huggingface.co/docs/transformers/perplexity) HF blog post because the blogpost code fails in at least the following circumstances:
- returns nans whenever the stride = 1
- hits a runtime error when the stride is significantly larger than the max model length (e.g. if max_model_length = 512 and stride = 1024)


Note that:
- As it is, it only works for causal models. Pseudoperplexity can be added later as another metric to work with masked language models.
- It takes in a list of strings so that it can be dataset independent. This does mean that it doesn't currently batch inputs, and is therefore relatively slow.
- It overwrites the metrics compute() function for a specific perplexity compute() function. This is because the current general metrics compute() function requires model-generated predictions, which doesn't make sense in the context of perplexity

Comments: Awesome thank you ! The implementation of the parent `Metric` class was assuming that all metrics were supposed to have references/predictions pairs - I just changed that so you don't have to override `compute()`. I took the liberty of doing the changes directly inside this PR to make sure it works as expected with perplexity.

Other than that it looks in pretty good shape :) I just did minor changes like remove a remaining `print` as well as fixing the `Features` defined in `_info()`. I also renamed `input_text` to `input_texts` since it makes it more obvious that it's a list of strings - let me know if it sounds good to you.

Let me know if you'd like to make other changes or if it's all good for you !

The test with the full test set seems to take too much time in the CI - maybe we can just select `split="test[:few_examples]"` (around 10 maybe ?)