kosiew commented on code in PR #19674:
URL: https://github.com/apache/datafusion/pull/19674#discussion_r2700602390
##########
datafusion/common/src/nested_struct.rs:
##########
@@ -204,51 +262,105 @@ pub fn validate_struct_compatibility(
source_fields: &[FieldRef],
target_fields: &[FieldRef],
) -> Result<()> {
+ let has_overlap = fields_have_name_overlap(source_fields, target_fields);
+ if !has_overlap {
+ if source_fields.len() != target_fields.len() {
+ return _plan_err!(
+ "Cannot cast struct with {} fields to {} fields without name
overlap; positional mapping is ambiguous",
+ source_fields.len(),
+ target_fields.len()
+ );
+ }
+
+ for (source_field, target_field) in
source_fields.iter().zip(target_fields.iter())
+ {
+ validate_field_compatibility(source_field, target_field)?;
+ }
+
+ return Ok(());
+ }
+
// Check compatibility for each target field
for target_field in target_fields {
// Look for matching field in source by name
if let Some(source_field) = source_fields
.iter()
.find(|f| f.name() == target_field.name())
{
- // Ensure nullability is compatible. It is invalid to cast a
nullable
- // source field to a non-nullable target field as this may discard
- // null values.
- if source_field.is_nullable() && !target_field.is_nullable() {
+ validate_field_compatibility(source_field, target_field)?;
+ } else {
+ // Target field is missing from source
+ // If it's non-nullable, we cannot fill it with NULL
+ if !target_field.is_nullable() {
return _plan_err!(
- "Cannot cast nullable struct field '{}' to non-nullable
field",
+ "Cannot cast struct: target field '{}' is non-nullable but
missing from source. \
+ Cannot fill with NULL.",
target_field.name()
);
}
- // Check if the matching field types are compatible
- match (source_field.data_type(), target_field.data_type()) {
- // Recursively validate nested structs
- (Struct(source_nested), Struct(target_nested)) => {
- validate_struct_compatibility(source_nested,
target_nested)?;
- }
- // For non-struct types, use the existing castability check
- _ => {
- if !arrow::compute::can_cast_types(
- source_field.data_type(),
- target_field.data_type(),
- ) {
- return _plan_err!(
- "Cannot cast struct field '{}' from type {} to
type {}",
- target_field.name(),
- source_field.data_type(),
- target_field.data_type()
- );
- }
- }
- }
}
- // Missing fields in source are OK - they'll be filled with nulls
}
// Extra fields in source are OK - they'll be ignored
Ok(())
}
+fn validate_field_compatibility(
+ source_field: &Field,
+ target_field: &Field,
+) -> Result<()> {
+ if source_field.data_type() == &DataType::Null {
+ return Ok(());
+ }
Review Comment:
Amended
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