cyberbeam524 commented on code in PR #21714:
URL: https://github.com/apache/datafusion/pull/21714#discussion_r3214652919
##########
datafusion/sql/src/statement.rs:
##########
@@ -530,11 +531,18 @@ impl<S: ContextProvider> SqlToRel<'_, S> {
.iter()
.zip(input_fields)
.map(|(field, input_field)| {
- cast(
- col(input_field.name()),
- field.data_type().clone(),
- )
- .alias(field.name())
+ let metadata =
+
FieldMetadata::new_from_field(field.as_ref());
+ let alias_metadata = if
metadata.is_empty() {
+ None
+ } else {
+ Some(metadata)
+ };
+ Expr::Cast(Cast::new_from_field(
+ Box::new(col(input_field.name())),
+ Arc::clone(field),
+ ))
+ .alias_with_metadata(field.name(),
alias_metadata)
Review Comment:
I’ve refactored this logic to address this metadata propagation concern. The
code now does a gated validation strategy based on checks on whether its an
extension type:
- For existing non-extensions types, it uses simple aliases or cast_to
calls, ensuring no new metadata is introduced and allows regression tests to
pass.
- For extension types, it uses check_metadata_with_storage_equal to verify
compatibility.
- If a conversion is necessary, it uses Cast::new_from_field(). This ensures
the resulting expression strictly adheres to the target field's metadata,
sanitizing the output and preventing unexpected propagation from the input.
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