Create README.md with duckDB and hf datasets examples

README.md

@@ -0,0 +1,154 @@
+---
+task_categories:
+- text-generation
+pretty_name: Common Crawl Host Index v2
+size_categories:
+- 10B<n<100B
+---
+
+# Common Crawl Host Index v2
+
+GitHub: https://github.com/commoncrawl/cc-host-index
+
+Each crawl, we generate a Host Index, which aggregates information about each web hosted visited during the crawl. The 
+information is aggregated from the Common Crawl [columnar index](https://commoncrawl.org/blog/index-to-warc-files-and-urls-in-columnar-format),
+[web graph](https://commoncrawl.org/web-graphs), and [raw crawler logs](https://data.commoncrawl.org).
+
+## Quickstart
+
+### Using duckdb:
+
+DuckDB can [read directly from Huggingface](https://huggingface.co/docs/hub/en/datasets-duckdb):
+
+```sql
+$ duckdb
+D FROM 'hf://datasets/commoncrawl/host-index-testing-v2/data/crawl=CC-MAIN-2025-18/*.parquet' LIMIT 3;
+┌─────────────────────┬─────────────┬────────────────┬────────────┬────────────────┬───┬───────────────────┬─────────────────┬───────────┬───────────────────┬─────────────────┐
+│ nutch_unfetched_pct │ fetch_other │ fetch_200_lote │ nutch_gone │ nutch_gone_pct │ … │ fetch_notModified │ nutch_redirPerm │ fetch_200 │ nutch_notModified │      crawl      │
+│        int8         │    int64    │     int64      │   int64    │      int8      │   │       int64       │      int64      │   int64   │       int64       │     varchar     │
+├─────────────────────┼─────────────┼────────────────┼────────────┼────────────────┼───┼───────────────────┼─────────────────┼───────────┼───────────────────┼─────────────────┤
+│                   0 │           0 │              0 │          3 │              7 │ … │                 0 │               0 │        18 │                 0 │ CC-MAIN-2025-18 │
+│                   6 │           0 │              8 │          0 │              0 │ … │                 0 │               0 │        10 │                41 │ CC-MAIN-2025-18 │
+│                  80 │           0 │              0 │          8 │             17 │ … │                 0 │               0 │         0 │                 0 │ CC-MAIN-2025-18 │
+├─────────────────────┴─────────────┴────────────────┴────────────┴────────────────┴───┴───────────────────┴─────────────────┴───────────┴───────────────────┴─────────────────┤
+│ 3 rows                                                                                                                                                 43 columns (10 shown) │
+└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+D SELECT surt_host_name FROM 'hf://datasets/commoncrawl/host-index-testing-v2/data/crawl=CC-MAIN-2025-18/*.parquet' LIMIT 3;
+┌──────────────────────┐
+│    surt_host_name    │
+│       varchar        │
+├──────────────────────┤
+│ ae,ebury             │
+│ be,echappeeduhainaut │
+│ au,com,echolaw       │
+└──────────────────────┘
+```
+
+### Using Hugging Face `datasets` library:
+
+"Streaming" mode (`streaming=True`) is recommended (see [the `datasets` docs](https://huggingface.co/docs/datasets/v4.4.1/en/stream)). This avoids the need to download all of the parquet files up-front.
+
+```python
+>>> from datasets import load_dataset
+>>> ds = load_dataset("commoncrawl/host-index-testing-v2", data_dir="data/crawl=CC-MAIN-2025-18", split="train", streaming=True)
+Resolving data files: 100%|████████████| 30/30 [00:00<00:00, 43614.95it/s]
+>>> print(next(iter(ds)))
+{'nutch_unfetched_pct': 0, 'fetch_other': 0, 'fetch_200_lote': 0, 'nutch_gone': 3, 'nutch_gone_pct': 7, 'robots_gone': 0, 'robots_5xx': 0, 'hcrank10': 3.446, 'warc_record_length_median': 32867, 'hcrank': 11908759.0, 'nutch_fetched': 42, 'nutch_notModified_pct': 0, 'robots_4xx': 0, 'nutch_redirTemp': 0, 'fetch_redirPerm': 2, 'fetch_4xx': 0, 'url_host_tld': 'ae', 'nutch_fetched_pct': 93, 'robots_notModified': 0, 'robots_other': 0, 'nutch_redirTemp_pct': 0, 'fetch_200_lote_pct': 0, 'nutch_numRecords': 45, 'robots_3xx': 0, 'robots_redirTemp': 0, 'warc_record_length_av': 31769, 'url_host_registered_domain': 'ebury.ae', 'surt_host_name': 'ae,ebury', 'nutch_redirPerm_pct': 0, 'fetch_redirTemp': 0, 'robots_200': 3, 'fetch_3xx': 0, 'fetch_5xx': 0, 'nutch_unfetched': 0, 'prank': 4.73550733982247e-09, 'fetch_gone': 0, 'prank10': 0.0, 'robots_redirPerm': 1, 'fetch_notModified': 0, 'nutch_redirPerm': 0, 'fetch_200': 18, 'nutch_notModified': 0}
+```
+
+## Use Cases
+
+### Example questions this index can answer
+
+- What's our history of crawling a particular website, or group of websites?
+- What popular websites have a lot of non-English content?
+- What popular websites seem to have so little content that we might need to execute javascript to crawl them?
+
+### Example questions that we'll use to improve our crawl
+
+- What's the full list of websites where more than half of the webpages are primarily not English?
+- What popular websites end our crawls with most of their crawl budget left uncrawled?
+
+### Example questions that future versions of this host index can answer
+
+- What websites have a lot of content in particular languages?
+- What websites have a lot of content with particular Unicode scripts?
+
+## Examples
+
+US Federal government websites in the *.gov domain (about 1,400 domains, y-axis scale is millions):
+
+![current-federal.txt_sum.png](https://commoncrawl.github.io/cc-host-index-media/current-federal.txt_sum.png)
+
+[See all graphs from this dataset](https://commoncrawl.github.io/cc-host-index-media/current-federal.txt.html)
+
+commoncrawl.org fetch. You can see that we revamped our website in CC-2023-14, which caused a lot of
+permanent redirects to be crawled in the next few crawls:
+
+![commoncrawl.org_fetch.png](https://commoncrawl.github.io/cc-host-index-media/commoncrawl.org_fetch.png)
+
+[See all graphs from this dataset](https://commoncrawl.github.io/cc-host-index-media/commoncrawl.org.html)
+
+### Python code examples
+
+More examples of how to use this dataset with Python can be found at the [Common Crawl Host Index GitHub repo](https://github.com/commoncrawl/cc-host-index).
+
+## Highlights of the Schema
+
+- There is a Hive-style partition on `crawl`, which is a crawl name like `CC-MAIN-2025-13`.
+- There is one row for every webhost in the web graph, even if we didn't crawl that website in that particular crawl
+- The primary key is `surt_host_name`, which stores the URL in [Sort-friendly URI Reordering Transform (SURT) format](http://crawler.archive.org/articles/user_manual/glossary.html#surt). For example, the URI `commoncrawl.org` -> becomes `org,commoncrawl)`.
+- There is also `url_host_tld`, which we recommend that you use whenever possible (eg `org` for commoncrawl.org) - it typically improves performance, significantly.
+- There are counts of what we stored in our archive (`warc`, `crawldiagnostics`, `robots`)
+ - `fetch_200, fetch_3xx, fetch_4xx, fetch_5xx, fetch_gone, fetch_notModified, fetch_other, fetch_redirPerm, fetch_redirTemp`
+ - `robots_200, robots_3xx, robots_4xx, robots_5xx, robots_gone, robots_notModified, robots_other, robots_redirPerm, robots_redirTemp`
+- There is ranking information from the [web graph](https://commoncrawl.org/web-graphs): harmonic centrality, page rank, and both normalized to a 0-10 scale
+  - `hcrank`, `prank`, `hcrank10`, `prank10`
+- There is a language summary (for now, just the count of languages other than English (LOTE))
+  - `fetch_200_lote, fetch_200_lote_pct`
+- For a subset of the numbers, there is a `foo_pct` (eg `fetch3xx_pct`) which can help you avoid doing math in SQL. It is an integer 0-100.
+- There are raw numbers from our crawler logs, which also reveal the crawl budget and if we exhausted it
+  - `nutch_fetched, nutch_gone, nutch_notModified, nutch_numRecords, nutch_redirPerm, nutch_redirTemp, nutch_unfetched`
+  - `nutch_fetched_pct, nutch_gone_pct, nutch_notModified_pct, nutch_redirPerm_pct, nutch_redirTemp_pct, nutch_unfetched_pct`
+- There is a size summary (average and median size (compressed))
+  - `warc_record_length_median, warc_record_length_av` (will be renamed to _avg in v3)
+
+The full schema is available here: [athena_schema.v2.sql](https://github.com/commoncrawl/cc-host-index).
+
+## Known bugs
+
+- Some of the partitions have a different schema from others, so you will get errors for some of the columns in some of
+the crawls. We recommend that you avoid using those crawls, and only use the columns you need.
+- When the S3 bucket is under heavy use, AWS Athena will sometimes throw 503 errors. We have yet to figure out how to increase the retry limit.
+- Hint: https://status.commoncrawl.org/ has graphs of S3 performance for the last day, week, and month.
+- The sort order is a bit messed up, so database queries take more time than they should.
+
+## Expected changes in test v3
+
+- `warc_record_length_av` will be renamed to `_avg` (that was a typo)
+- more `_pct` columns
+- count truncations: length, time, disconnect, unspecified
+- addition of indegree and outdegree from the web graph
+- improve language details to be more than only LOTE and LOTE\_pct
+  - `content_language_top`, `content_language_top_pct`
+- add unicode block information, similar to languages
+- `prank10` needs its power law touched up (`hcrank10` might change too)
+- there's a sort problem that .com shards have a smattering of not-.com hosts. This hurts performance.
+- add domain prank/hcrank
+- CI running against S3
+- `robots_digest_count_distinct`
+- `robots_digest` (if there is exactly 1 robots digest)
+- Summarize `fetch_redirect`: same surt, same surt host, other.
+
+## Contributing
+
+We'd love to get testing and code contributions! Here are some clues:
+
+- We'd love to hear if you tried it out, and what your comments are
+- We'd love to have python examples using Athena, similar to duckdb
+- We'd love to have more python examples
+- Please use pyarrow whenever possible
+
+## Terms of Use
+
+[https://commoncrawl.org/terms-of-use](https://commoncrawl.org/terms-of-use)