adriangb commented on code in PR #24125:
URL: https://github.com/apache/datafusion/pull/24125#discussion_r3770160182
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datafusion/physical-expr-adapter/src/schema_rewriter.rs:
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@@ -273,6 +273,35 @@ struct DefaultPhysicalExprAdapterRewriter {
physical_file_schema: SchemaRef,
}
+/// Outcome of walking a `get_field` key path through nested struct fields.
+enum FieldPathResolution<'a> {
+ /// The leaf field the path points at.
+ Found(&'a FieldRef),
+ /// Some key along the path does not exist, so the access reads as null.
+ Missing,
+ /// An intermediate field is not a struct, so the path cannot be resolved
+ /// statically.
+ NotAStruct,
+}
+
+/// Follow a `get_field` key path (`['a', 'b']` for `s['a']['b']`) through
+/// nested struct fields.
+fn resolve_field_path<'a>(fields: &'a Fields, path: &[&str]) ->
FieldPathResolution<'a> {
+ let Some((field_name, rest)) = path.split_first() else {
+ return FieldPathResolution::NotAStruct;
Review Comment:
Good point. I fixed it by taking the first path as it's own parameter,
making the state unrepresentable.
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