hsiang-c commented on code in PR #2865:
URL: https://github.com/apache/iceberg-rust/pull/2865#discussion_r3632401549
##########
crates/iceberg/src/metadata_columns.rs:
##########
@@ -478,15 +484,26 @@ pub fn is_metadata_field(field_id: i32) -> bool {
)
}
-/// Checks if a column name is a metadata column.
+/// Checks if a column name is a metadata column of a data table.
+///
+/// Only the `_`-prefixed reserved names (`_file`, `_pos`, `_partition`,
`_spec_id`,
+/// `_deleted`, and the changelog/row-lineage columns) are metadata columns
that can be
+/// projected in a data-table scan. Per the Iceberg spec, reserved metadata
column names
+/// are `_`-prefixed precisely so they cannot collide with user data columns.
+///
+/// The bare names `pos` and `file_path` are the internal columns of a
position-delete
+/// file, not projectable metadata columns of a data table, so they are
excluded here even
+/// though [`get_metadata_field_id`] still maps them to their reserved field
ids. Without
+/// this exclusion a real data column named `pos` or `file_path` would be
shadowed and fail
+/// to scan.
///
/// # Arguments
/// * `column_name` - The column name to check
///
/// # Returns
-/// `true` if the column name is a metadata column, `false` otherwise
+/// `true` if the column name is a projectable data-table metadata column,
`false` otherwise
pub fn is_metadata_column_name(column_name: &str) -> bool {
- get_metadata_field_id(column_name).is_ok()
+ column_name.starts_with('_') && get_metadata_field_id(column_name).is_ok()
Review Comment:
(nit) Shall we follow Iceberg Java's logic:
https://github.com/apache/iceberg/blob/apache-iceberg-1.11.0/core/src/main/java/org/apache/iceberg/MetadataColumns.java#L145-L151
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