alamb commented on code in PR #13063:
URL: https://github.com/apache/datafusion/pull/13063#discussion_r1815673753
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datafusion/core/src/datasource/schema_adapter.rs:
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@@ -79,11 +87,17 @@ pub trait SchemaAdapter: Send + Sync {
) -> datafusion_common::Result<(Arc<dyn SchemaMapper>, Vec<usize>)>;
}
-/// Maps, by casting or reordering columns from the file schema to the table
-/// schema.
+/// Maps, columns from the file schema to the table schema.
+///
+/// See [`DefaultSchemaAdapterFactory`] for more details and examples.
pub trait SchemaMapper: Debug + Send + Sync {
- /// Adapts a `RecordBatch` to match the `table_schema` using the stored
- /// mapping and conversions.
+ /// Adapts a `RecordBatch` to match the `table_schema`
+ ///
+ /// # Errors:
+ ///
+ /// * If a column in the table schema is non-nullable but is not present
+ /// in the file schema (i.e. it is missing), this method tries to fill it
+ /// with nulls resulting in a schema error
Review Comment:
It is a good call -- tried to clarify in d966fd112
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