nevi-me commented on code in PR #1922:
URL: https://github.com/apache/arrow-rs/pull/1922#discussion_r905412286
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arrow/src/compute/kernels/cast.rs:
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@@ -72,9 +72,9 @@ pub fn can_cast_types(from_type: &DataType, to_type:
&DataType) -> bool {
// cast one decimal type to another decimal type
(Decimal(_, _), Decimal(_, _)) => true,
// signed numeric to decimal
- (Int8 | Int16 | Int32 | Int64 | Float32 | Float64, Decimal(_, _)) |
+ (Null|Int8 | Int16 | Int32 | Int64 | Float32 | Float64, Decimal(_, _))
|
// decimal to signed numeric
- (Decimal(_, _), Int8 | Int16 | Int32 | Int64 | Float32 | Float64)
+ (Decimal(_, _), Null| Int8 | Int16 | Int32 | Int64 | Float32 | Float64)
Review Comment:
The initial null cast was so that I could write `NullArray` in parquet,
which we write as `Int32Array` that's all null.
I think casting null to types is helpful, but other types to null could be a
footgun as it causes data loss. So I'd be in favour of removing it. Users who
need to do that can always create a separate function that just creates a null
array of `array.len()` as it'd have no buffers anyway.
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