comphead commented on code in PR #3269:
URL: https://github.com/apache/iceberg-rust/pull/3269#discussion_r4232334192
##########
crates/iceberg/src/arrow/reader/projection.rs:
##########
@@ -422,6 +422,16 @@ pub(super) fn apply_name_mapping_to_arrow_schema(
"Schema already has field IDs - name mapping should not be applied"
);
+ let mut field_ids_by_name = HashMap::new();
Review Comment:
Nit: this map is rebuilt for every file and costs `O(mapped names)` hashing
and allocation up front, whereas the old scan cost `O(arrow fields × mapped
fields)` with early exit. For a file with a handful of columns against a very
wide table mapping, the index may not win. I have not measured that case, so
treat it as a question. If you keep the index,
`HashMap::with_capacity(name_mapping.fields().len())` avoids rehash growth
while it fills.
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