comphead commented on code in PR #3303:
URL: https://github.com/apache/iceberg-rust/pull/3303#discussion_r4157920270
##########
crates/iceberg/src/arrow/schema.rs:
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@@ -1320,6 +1306,12 @@ impl ArrowSchemaVisitor for MetadataStripVisitor {
/// including nested struct, list, and map fields. This is useful for schema
comparison
/// where metadata differences should be ignored.
///
+/// Two other differences are normalized away too, so that schemas that differ
only in
+/// them compare equal once stripped:
+/// - A map's entries field is renamed to [`DEFAULT_MAP_FIELD_NAME`] and made
non-nullable,
+/// as [`schema_to_arrow_schema`] builds it. Its key and value fields keep
their names.
Review Comment:
This says map key and value names are kept, but it is silent on list element
names. Are they kept on purpose? arrow-rs names list elements `item`
(`Field::new_list_field`) and `schema_to_arrow_schema` names them `element`, so
a stripped `List(item)` still differs from a stripped table `List(element)`.
If keeping them is the intent, one more sentence here would complete the
contract. If callers need them normalized, `LIST_FIELD_NAME` is the name to
rebuild with. That may not matter for datafusion-iceberg if DataFusion already
casts the input to the table's nested names, which is unverified.
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