chore: hoist boolean -> string cast (#14122)

crates/polars-arrow/src/compute/cast/boolean_to.rs

@@ -1,7 +1,7 @@
 use polars_error::PolarsResult;
 
-use crate::array::{Array, BinaryArray, BooleanArray, PrimitiveArray, Utf8Array};
-use crate::offset::Offset;
+use super::{ArrayFromIter, BinaryViewArray, Utf8ViewArray};
+use crate::array::{Array, BooleanArray, PrimitiveArray};
 use crate::types::NativeType;
 
 pub(super) fn boolean_to_primitive_dyn<T>(array: &dyn Array) -> PolarsResult<Box<dyn Array>>
@@ -26,24 +26,26 @@ where
     PrimitiveArray::<T>::new(T::PRIMITIVE.into(), values.into(), from.validity().cloned())
 }
 
-/// Casts the [`BooleanArray`] to a [`Utf8Array`], casting trues to `"1"` and falses to `"0"`
-pub fn boolean_to_utf8<O: Offset>(from: &BooleanArray) -> Utf8Array<O> {
-    let iter = from.values().iter().map(|x| if x { "1" } else { "0" });
-    Utf8Array::from_trusted_len_values_iter(iter)
+pub fn boolean_to_utf8view(from: &BooleanArray) -> Utf8ViewArray {
+    unsafe { boolean_to_binaryview(from).to_utf8view_unchecked() }
 }
 
-pub(super) fn boolean_to_utf8_dyn<O: Offset>(array: &dyn Array) -> PolarsResult<Box<dyn Array>> {
+pub(super) fn boolean_to_utf8view_dyn(array: &dyn Array) -> PolarsResult<Box<dyn Array>> {
     let array = array.as_any().downcast_ref().unwrap();
-    Ok(Box::new(boolean_to_utf8::<O>(array)))
+    Ok(boolean_to_utf8view(array).boxed())
 }
 
 /// Casts the [`BooleanArray`] to a [`BinaryArray`], casting trues to `"1"` and falses to `"0"`
-pub fn boolean_to_binary<O: Offset>(from: &BooleanArray) -> BinaryArray<O> {
-    let iter = from.values().iter().map(|x| if x { b"1" } else { b"0" });
-    BinaryArray::from_trusted_len_values_iter(iter)
+pub fn boolean_to_binaryview(from: &BooleanArray) -> BinaryViewArray {
+    let iter = from.iter().map(|opt_b| match opt_b {
+        Some(true) => Some("true".as_bytes()),
+        Some(false) => Some("false".as_bytes()),
+        None => None,
+    });
+    BinaryViewArray::arr_from_iter_trusted(iter)
 }
 
-pub(super) fn boolean_to_binary_dyn<O: Offset>(array: &dyn Array) -> PolarsResult<Box<dyn Array>> {
+pub(super) fn boolean_to_binaryview_dyn(array: &dyn Array) -> PolarsResult<Box<dyn Array>> {
     let array = array.as_any().downcast_ref().unwrap();
-    Ok(Box::new(boolean_to_binary::<O>(array)))
+    Ok(boolean_to_binaryview(array).boxed())
 }

crates/polars-arrow/src/compute/cast/mod.rs

@@ -462,8 +462,8 @@ pub fn cast(
             Int64 => boolean_to_primitive_dyn::<i64>(array),
             Float32 => boolean_to_primitive_dyn::<f32>(array),
             Float64 => boolean_to_primitive_dyn::<f64>(array),
-            LargeUtf8 => boolean_to_utf8_dyn::<i64>(array),
-            LargeBinary => boolean_to_binary_dyn::<i64>(array),
+            Utf8View => boolean_to_utf8view_dyn(array),
+            BinaryView => boolean_to_binaryview_dyn(array),
             _ => polars_bail!(InvalidOperation:
                 "casting from {from_type:?} to {to_type:?} not supported",
             ),

crates/polars-core/src/chunked_array/cast.rs

@@ -360,24 +360,9 @@ impl ChunkCast for BinaryOffsetChunked {
     }
 }
 
-fn boolean_to_string(ca: &BooleanChunked) -> StringChunked {
-    ca.into_iter()
-        .map(|opt_b| match opt_b {
-            Some(true) => Some("true"),
-            Some(false) => Some("false"),
-            None => None,
-        })
-        .collect()
-}
-
 impl ChunkCast for BooleanChunked {
     fn cast(&self, data_type: &DataType) -> PolarsResult<Series> {
         match data_type {
-            DataType::String => {
-                let mut ca = boolean_to_string(self);
-                ca.rename(self.name());
-                Ok(ca.into_series())
-            },
             #[cfg(feature = "dtype-struct")]
             DataType::Struct(fields) => cast_single_to_struct(self.name(), &self.chunks, fields),
             _ => cast_impl(self.name(), &self.chunks, data_type),