dynamic_bucket_partitioning/README.md

Dynamic Bucket Partitioning

Register language buckets as Dagster dynamic partitions and materialize a partition-scoped report for each bucket.

What this example shows

• Defining a DynamicPartitionsDefinition
• Loading a multilingual Hub dataset with @hf_dataset_asset
• Modeling language or route buckets as Dagster partitions
• Reading context.partition_key inside a partitioned asset
• Keeping raw ingestion separate from per-bucket reporting

Dataset

Helsinki-NLP/opus_books - a multilingual parallel text dataset built from translated books. The dataset is useful for examples where language pairs or locales need to become operational routing keys.

Asset	Description
opus_books_raw	Loads the train split from the Hub
partition_report	Emits metadata for one dynamic partition key

Asset graph

opus_books_raw

partition_report[language_partitions]

partition_report is intentionally independent from opus_books_raw in this minimal example. In a production pipeline, the partitioned asset would usually filter the raw dataset to the selected language bucket.

Key API

language_partitions = DynamicPartitionsDefinition(
    name="language_partitions"
)

@asset(
    partitions_def=language_partitions,
    group_name="dynamic_bucket_partitioning",
)
def partition_report(context: AssetExecutionContext) -> MaterializeResult:
    partition = context.partition_key

    return MaterializeResult(metadata={"partition": partition})

Dynamic partitions are created at runtime, which makes them a good fit for datasets whose language set, customer set, or source buckets are discovered after deployment.

Example partition keys

Partition key	Meaning
en-fr	English/French bucket
en-de	English/German bucket
es-en	Spanish/English bucket

Add keys from the Dagster UI before materializing partition_report.

Storage layout

.dagster_hf_storage/
└── opus_books_raw/

partition_report returns metadata only, so it is not persisted by the Hugging Face IO manager.

How to run

cd dagster_hf_datasets_examples

dagster dev -m dynamic_bucket_partitioning.definitions

In the Dagster UI, open Assets, select partition_report, add one or more dynamic partition keys, then materialize the selected partitions.