Spark DataFrame Schema Nullable Fields

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In general Spark Datasets either inherit nullable property from its parents, or infer based on the external data types.

You can argue if it is a good approach or not but ultimately it is sensible. If semantics of a data source doesn’t support nullability constraints, then application of a schema cannot either. At the end of the day it is always better to assume that things can be null, than fail on the runtime if this the opposite assumption turns out to be incorrect.

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