Improve the projection operation and add explicit validation #842
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This is important in the context of Samples which have no Data for an Index variable. Using filter all over seemed messy and error-prone.
lindholc
reviewed
Jan 9, 2026
lindholc
reviewed
Jan 9, 2026
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The primary goal here is to make projection operations more robust. I added a
validatemethod to encapsulate all the reasons that a projection is not compatible with a dataset's model. One breaking change is that this will not allow a projection for an undefined variable. This is consistent with relational algebra and SQL. I also cleaned up and clarified a few things.We might want to use this validation pattern for all
Operations, callingvalidatewhen applying them to a dataset. Otherwise, I've thought about constructing the operations with the model so we can make them safe by construction.I also paid off some debt by beefing up
Tupleconstruction to disallow elements with duplicate ids and adding anonIndexScalarsmethod forDataTypes to clean up all the places that filter was being used. And fixed a deprecation.