Hello Palantir Community,
I am encountering a build failure in Foundry related to the Start_TS property. Below is a summary of the issue and the troubleshooting steps I have taken.
Summary of Error:
The build failed due to a type mismatch in the property Start_TS. The system expected an offsetdatetimeudt type, but the field is being treated as a struct type during transformation/output generation. Because of this mismatch, the ontology build fails.
What I Observed:
When I import the dataset, Start_TS has values like 2026-03-26T02:45:52.604Z and Foundry identifies the type as datetime. However, after I transform the dataset or generate the output dataset, Foundry changes the datatype of this field to struct. Later, when I try to build the ontology type and ontology objects, Foundry expects this field to be offsetdatetimeudt, which causes the build to fail.
Why the Failure May Be Happening:
It looks like the source dataset initially has the column in a datetime-compatible format, but during transformation or output dataset generation, the schema for Start_TS is being converted into a struct instead of remaining as a timestamp/datetime field. As a result, the ontology expects offsetdatetimeudt, but the transformed dataset provides struct, creating a schema mismatch between the dataset and the ontology definition.
Troubleshooting Steps Taken:
I checked the source dataset and confirmed that Start_TS is originally shown as datetime.
I noticed that after transformation, the field changes to struct.
I attempted to correct the mismatch by transforming Start_TS into the expected type.
I used code to cast/convert the column, but the ontology build still fails due to the datatype mismatch.
Question:
How can I make sure that Start_TS stays as offsetdatetimeudt (or a compatible datetime/timestamp type) in the transformed/output dataset instead of being converted to struct? Has anyone faced a similar issue while building ontology types and ontology objects in Foundry?