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# ask-ai
b

Brent Shulman

02/19/2024, 6:24 PM
I have two assets that use different partitions defs. How can I union them together
s

Scout

02/19/2024, 6:24 PM
In Dagster, assets can be partitioned by different partition definitions, which describe how the data is sliced into distinct logical units. If you have two assets with different partition definitions and you want to union them together, you would typically need to ensure that they can be combined in a meaningful way. The documentation provides an example of how to combine
AssetSelection
objects using operators like
|
(union),
&
(intersection), and
-
(difference). Here's an example from the documentation on how to use the union operator:
Copy code
python remit_professional_pipeline = define_asset_job(     name="Remit_Professional_Build",     selection=(         remit_professional_asset_selector | remit_professional_end_table_selector     ), )
However, this example assumes that the assets being combined are compatible in terms of their partitioning schemes or that they do not require partitioning alignment. If the assets have different partition definitions, combining them directly may not be straightforward because each partition represents a different slice of data, and the union operation may not make sense across different partitioning schemes. If you need to combine assets with different partition definitions, you might need to consider transforming one or both assets to align their partitioning schemes or to remove partitioning from one of them, depending on your use case. This could involve creating a new asset that represents the union of the data from both original assets, with a partitioning scheme that makes sense for the combined data. The documentation does not provide a direct example of how to union assets with different partition definitions, as this is a more complex scenario that would depend on the specific nature of the partitions and the intended use of the combined data. If you need further guidance on how to handle this specific use case, you may want to consult the Dagster community or explore more advanced features of the platform that could help in aligning partition definitions.
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