Issue with mongo
https://huggingface.co/datasets/circa

```
Message:       Tried to save duplicate unique keys (E11000 duplicate key error collection: datasets_preview_cache.rows index: dataset_name_1_config_name_1_split_name_1_row_idx_1 dup key: { dataset_name: "circa", config_name: "default", split_name: "train", row_idx: 0 }, full error: {'index': 0, 'code': 11000, 'keyPattern': {'dataset_name': 1, 'config_name': 1, 'split_name': 1, 'row_idx': 1}, 'keyValue': {'dataset_name': 'circa', 'config_name': 'default', 'split_name': 'train', 'row_idx': 0}, 'errmsg': 'E11000 duplicate key error collection: datasets_preview_cache.rows index: dataset_name_1_config_name_1_split_name_1_row_idx_1 dup key: { dataset_name: "circa", config_name: "default", split_name: "train", row_idx: 0 }'})
```

Issue with mongo: https://huggingface.co/datasets/circa

```
Message:       Tried to save duplicate unique keys (E11000 duplicate key error collection: datasets_preview_cache.rows index: dataset_name_1_config_name_1_split_name_1_row_idx_1 dup key: { dataset_name: "circa", config_name: "default", split_name: "train", row_idx: 0 }, full error: {'index': 0, 'code': 11000, 'keyPattern': {'dataset_name': 1, 'config_name': 1, 'split_name': 1, 'row_idx': 1}, 'keyValue': {'dataset_name': 'circa', 'config_name': 'default', 'split_name': 'train', 'row_idx': 0}, 'errmsg': 'E11000 duplicate key error collection: datasets_preview_cache.rows index: dataset_name_1_config_name_1_split_name_1_row_idx_1 dup key: { dataset_name: "circa", config_name: "default", split_name: "train", row_idx: 0 }'})
```
