mbutrovich commented on code in PR #22026:
URL: https://github.com/apache/datafusion/pull/22026#discussion_r3191251780
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datafusion/datasource/src/table_schema.rs:
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@@ -63,6 +70,15 @@ pub struct TableSchema {
/// this field holds that schema.
file_schema: SchemaRef,
+ /// Virtual columns that are generated by the reader rather than read from
+ /// the data files or the directory structure.
+ ///
+ /// For example, a Parquet reader may inject a `row_number` column whose
+ /// values are produced per file by the reader. Virtual column fields must
+ /// carry an arrow extension type (e.g. `RowNumber`, `RowGroupIndex`) so
the
+ /// file reader can recognize them.
+ virtual_columns: Arc<Vec<FieldRef>>,
Review Comment:
Will do, thanks!
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