SpecificPartitionMapping between static-partitioned asset and multi-partitioned asset

[dagsir[bot]]

Hi all, confused about out how to deal with a partition-mapping scenario. I have an upstream asset: say asset_multi that is multi-dimensioned (one dim is dynamic and one is static). I have another asset with another static single dimension (asset_single). I want to create a downstream asset with a multi dimension where one dimension is identically mapped to asset_single and the other dimension is just the multi-dimensioned collapsed to one the way the multi-part key does it (with | delimiter).

asset_multi keys: <a, 0>, <a, 1>
asset_single keys: <x>, <y>

desired downstream asset keys:
a|0 , x
a|1 , x
a|0 , y
a|1 , y

What is the expected way to solve this given we cant have 3-dim multi-parts?

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The question was originally asked in Dagster Slack.

[sryza]

@clairelin135 do you know if this exists yet? E.g. something like MultiToSingleDimensionPartitionMapping but with the ability to set the mapping for one of the dimensions to be a SpecificPartitionMapping?

[clairelin135]

Unfortunately not, MultiToSingleDimensionPartitionMapping currently assumes that the single-dimension partitions def is a dimension of the multipartitions def

It's fairly straightforward to implement this though -- BaseMultiPartitionMapping (which MultiToSingleDimensionPartitionMapping inherits from) already has the ability to accept partition mappings between specific dimensions. The main open question is what the API of MultiToSingleDimensionPartitionMapping would look like