alamb commented on code in PR #8871:
URL: https://github.com/apache/arrow-rs/pull/8871#discussion_r2543061254
##########
arrow-cast/src/cast/mod.rs:
##########
@@ -221,12 +221,34 @@ pub fn can_cast_types(from_type: &DataType, to_type:
&DataType) -> bool {
Decimal32(_, _) | Decimal64(_, _) | Decimal128(_, _) |
Decimal256(_, _),
) => true,
(Struct(from_fields), Struct(to_fields)) => {
- from_fields.len() == to_fields.len()
- && from_fields.iter().zip(to_fields.iter()).all(|(f1, f2)| {
+ if from_fields.len() != to_fields.len() {
+ return false;
+ }
+
+ // fast path, all field names are in the same order and same
number of fields
+ if from_fields
+ .iter()
+ .zip(to_fields.iter())
+ .all(|(f1, f2)| f1.name() == f2.name())
+ {
+ return from_fields.iter().zip(to_fields.iter()).all(|(f1, f2)|
{
// Assume that nullability between two structs are
compatible, if not,
// cast kernel will return error.
can_cast_types(f1.data_type(), f2.data_type())
- })
+ });
+ }
+
+ // slow path, we match the fields by name
Review Comment:
I think one idea that has come up in the past is to do this mapping
calculation once and then use it for both can_cast_types and cast
However, this seems to be strictly better than current main (doesn't slow
down existing code and allows more uses, so 👍 to me)
##########
arrow-cast/src/cast/mod.rs:
##########
@@ -10836,11 +10890,11 @@ mod tests {
let int = Arc::new(Int32Array::from(vec![42, 28, 19, 31]));
let struct_array = StructArray::from(vec![
(
- Arc::new(Field::new("b", DataType::Boolean, false)),
+ Arc::new(Field::new("a", DataType::Boolean, false)),
Review Comment:
why this change?
##########
arrow-cast/src/cast/mod.rs:
##########
@@ -10884,11 +10938,11 @@ mod tests {
let int = Arc::new(Int32Array::from(vec![Some(42), None, Some(19),
None]));
let struct_array = StructArray::from(vec![
(
- Arc::new(Field::new("b", DataType::Boolean, false)),
+ Arc::new(Field::new("a", DataType::Boolean, false)),
Review Comment:
likewise why was this test changed?
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