Common Crawl - Malayalam

Useful tools for extracting malayalam text from the Common Crawl Dataset

Running on AWS

• AWS ATHENA can be used to query the cc index table to get the offsets of warc records with Malayalam content in a CSV file. The query results would be available in S3.

-- For malayalam primary / secondary of January 2020 --  
-- If only primary is needed, use content_language LIKE 'mal%' --  
  
SELECT url,  
 warc_filename, warc_record_offset, warc_record_lengthFROM "ccindex"."ccindex"  
WHERE (crawl = 'CC-MAIN-2020-05 ')  
 AND subset = 'warc' AND content_languages LIKE '%mal%'

• After you have the csv, an AWS EMR cluster can be spun up to retrieve the records from WARC files hosted in S3. The spark-submit job can be submitted using the following parameters. The app JAR is available in the repo (artifacts/cc-index-table-0.2-SNAPSHOT-jar-with-dependencies.jar)
  or you can build it from source using maven.

> spark-submit --class org.commoncrawl.spark.examples.CCIndexWarcExport $APPJAR \ 
--csv s3://<input_csv_path> --numOutputPartitions 24 --numRecordsPerWarcFile -1 \
--warcPrefix MALAYALAM-CC-2020-05 s3://commoncrawl/cc-index/table/cc-main/warc/  s3://<output_path>  

• The spark job writes the extracted WARC files back to s3 and will be available at s3://<output_path>.

• For cleaning the extracted HTML content, a library such as selectolax can be used. A reference script is available at [src/process_warc_batch.py].

• The script can be run from an EC2 instance. The files after processing are compressed and written back to s3 and can be downloaded to your local machine.

Usage

We are including a couple of scripts to easily execute these commands in AWS. All you have to provide is the AWS credentials and the path of the S3 bucket.

• First, run extract_malayalam_warcs.sh as follows:

./extract_malayalam_warcs.sh <AWS Secret Key ID> <AWS Secret Key> <Crawl ID> <S3 Bucket Root Path> <Previously processed csv>


* Here, you can also provide any previously processed csv as the last optional argument. This helps in avoiding fetching  duplicate crawled urls.
* After you run the above script, you would have the WARC files in S3.
* In order to extract the malayalam content, you can either download the WARC files back to your machine or spin up an
EC2 instance and process it there. EC2 instance with Ubuntu Server 18.04 AMI with atleast 50 GB of storage and type m5.large is preferred.
* We are also providing a handy script to extract malayalam content in filter_malayalam.sh. Its usage is as follows:-
```buildoutcfg
./filter_malayalam.sh <AWS Secret Key ID> <AWS Secret Key> <S3 Warc Folder> <S3 Out Directory>
PS: Do not include trailing slashes in the S3 paths. Eg:- s3://nlp-mal/2019-51/output

Public Dataset

We have run these scripts on some months of the Common Crawl archives and are making it publicly available. Please find the cleaned up corpus below:

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Common Crawl Date	Link to Cleaned Dataset
2020-10	https://calicut.qburst.in/commoncrawl/malayalam/2020-10/
2020-05	https://calicut.qburst.in/commoncrawl/malayalam/2020-05/
2019-51	https://calicut.qburst.in/commoncrawl/malayalam/2019-51/
2019-47	https://calicut.qburst.in/commoncrawl/malayalam/2019-47/
2019-43	https://calicut.qburst.in/commoncrawl/malayalam/2019-43/

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