liukun4515 commented on code in PR #2376:
URL: https://github.com/apache/arrow-rs/pull/2376#discussion_r941925548
##########
arrow/src/compute/kernels/cast.rs:
##########
@@ -1252,34 +1265,125 @@ const fn time_unit_multiple(unit: &TimeUnit) -> i64 {
}
/// Cast one type of decimal array to another type of decimal array
-fn cast_decimal_to_decimal(
+fn cast_decimal_to_decimal<const BYTE_WIDTH1: usize, const BYTE_WIDTH2: usize>(
array: &ArrayRef,
input_scale: &usize,
output_precision: &usize,
output_scale: &usize,
) -> Result<ArrayRef> {
- let array = array.as_any().downcast_ref::<Decimal128Array>().unwrap();
-
- let output_array = if input_scale > output_scale {
+ if input_scale > output_scale {
// For example, input_scale is 4 and output_scale is 3;
// Original value is 11234_i128, and will be cast to 1123_i128.
let div = 10_i128.pow((input_scale - output_scale) as u32);
- array
- .iter()
- .map(|v| v.map(|v| v.as_i128() / div))
- .collect::<Decimal128Array>()
+ if BYTE_WIDTH1 == 16 {
+ let array =
array.as_any().downcast_ref::<Decimal128Array>().unwrap();
+ let iter = array.iter().map(|v| v.map(|v| v.as_i128() / div));
+ if BYTE_WIDTH2 == 16 {
+ let output_array = iter
+ .collect::<Decimal128Array>()
+ .with_precision_and_scale(*output_precision,
*output_scale)?;
+
+ Ok(Arc::new(output_array))
+ } else {
+ let output_array = iter
+ .map(|v| v.map(BigInt::from))
+ .collect::<Decimal256Array>()
+ .with_precision_and_scale(*output_precision,
*output_scale)?;
+
+ Ok(Arc::new(output_array))
+ }
+ } else {
+ let array =
array.as_any().downcast_ref::<Decimal256Array>().unwrap();
+ let iter = array.iter().map(|v| v.map(|v|
v.to_big_int().div(div)));
+ if BYTE_WIDTH2 == 16 {
+ let values = iter
+ .map(|v| {
+ if v.is_none() {
+ Ok(None)
+ } else {
+ v.and_then(|v| v.to_i128())
+ .ok_or_else(|| {
+ ArrowError::InvalidArgumentError(
+ "Cannot be casted to 128-bit integer for
Decimal128"
+ .to_string(),
Review Comment:
```suggestion
format!("{:?} cannot be casted to
128-bit integer for Decimal128", v)
```
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