coderfender commented on issue #3459:
URL:
https://github.com/apache/datafusion-comet/issues/3459#issuecomment-3874427981
@andygrove , the goal here is to eshtablish a trait / contract for cast
operations through a trait . Example as follows
Boolean module (boolean.rs)
```
use super::traits::SparkCast;
use super::utils::is_boolean;
pub struct BooleanCast;
impl SparkCast for BooleanCast {
fn can_cast(&self, from: &DataType, to: &DataType) -> bool {
is_boolean(from) || is_boolean(to)
}
fn cast(
&self,
array: &ArrayRef,
from: &DataType,
to: &DataType,
opts: &SparkCastOptions,
) -> SparkResult<ArrayRef> {
match (from, to) {
// Boolean -> other types
(Boolean, Int8) => self.boolean_to_int8(array),
(Boolean, Int16) => self.boolean_to_int16(array),
(Boolean, Int32) => self.boolean_to_int32(array),
(Boolean, Int64) => self.boolean_to_int64(array),
(Boolean, Float32) => self.boolean_to_float32(array),
(Boolean, Float64) => self.boolean_to_float64(array),
(Boolean, Utf8) => self.boolean_to_string(array),
// Other types -> Boolean
(Int8 | Int16 | Int32 | Int64, Boolean) =>
self.int_to_boolean(array),
(Utf8, Boolean) => self.string_to_boolean(array, opts),
(Decimal128(_, _), Boolean) => self.decimal_to_boolean(array),
_ => Err(SparkError::Internal(format!(
"BooleanCast: unsupported {} -> {}", from, to
))),
}
}
}
impl BooleanCast {
fn boolean_to_int8(&self, array: &ArrayRef) -> SparkResult<ArrayRef> {
<implentation details>
}
fn string_to_boolean(&self, array: &ArrayRef, opts: &SparkCastOptions)
-> SparkResult<ArrayRef> {
// <implentation details>
}
// other methods
}
on the caller side `cast.rs` / `mod.rs`
```
pub fn spark_cast(
array: &ArrayRef,
from: &DataType,
to: &DataType,
opts: &SparkCastOptions,
) -> SparkResult<ArrayRef> {
match from {
_ if is_boolean(from) => BooleanCast.cast.cast(array, from, to,
opts),
_ if is_string(from) => StringCast.cast(array, from, to, opts),
_ if is_numeric(from) => NumericCast.cast(array, from, to, opts),
// ... other data types
}
}
```
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