Replace checked casts with as for performance (#1918)

Remove num dependency from arrow-buffer

Deprecate unnecessary methods

arrow-array/src/array/dictionary_array.rs

@@ -308,20 +308,13 @@ impl<K: ArrowPrimitiveType> DictionaryArray<K> {
 
     /// Return an iterator over the keys (indexes into the dictionary)
     pub fn keys_iter(&self) -> impl Iterator<Item = Option<usize>> + '_ {
-        self.keys
-            .iter()
-            .map(|key| key.map(|k| k.to_usize().expect("Dictionary index not usize")))
+        self.keys.iter().map(|key| key.map(|k| k.as_usize()))
     }
 
     /// Return the value of `keys` (the dictionary key) at index `i`,
     /// cast to `usize`, `None` if the value at `i` is `NULL`.
     pub fn key(&self, i: usize) -> Option<usize> {
-        self.keys.is_valid(i).then(|| {
-            self.keys
-                .value(i)
-                .to_usize()
-                .expect("Dictionary index not usize")
-        })
+        self.keys.is_valid(i).then(|| self.keys.value(i).as_usize())
     }
 
     /// Downcast this dictionary to a [`TypedDictionaryArray`]
@@ -586,7 +579,7 @@ where
 
     unsafe fn value_unchecked(&self, index: usize) -> Self::Item {
         let val = self.dictionary.keys.value_unchecked(index);
-        let value_idx = val.to_usize().unwrap();
+        let value_idx = val.as_usize();
 
         // As dictionary keys are only verified for non-null indexes
         // we must check the value is within bounds

arrow-array/src/array/list_array.rs

@@ -80,18 +80,16 @@ impl<OffsetSize: OffsetSizeTrait> GenericListArray<OffsetSize> {
     /// # Safety
     /// Caller must ensure that the index is within the array bounds
     pub unsafe fn value_unchecked(&self, i: usize) -> ArrayRef {
-        let end = *self.value_offsets().get_unchecked(i + 1);
-        let start = *self.value_offsets().get_unchecked(i);
-        self.values
-            .slice(start.to_usize().unwrap(), (end - start).to_usize().unwrap())
+        let end = self.value_offsets().get_unchecked(i + 1).as_usize();
+        let start = self.value_offsets().get_unchecked(i).as_usize();
+        self.values.slice(start, end - start)
     }
 
     /// Returns ith value of this list array.
     pub fn value(&self, i: usize) -> ArrayRef {
-        let end = self.value_offsets()[i + 1];
-        let start = self.value_offsets()[i];
-        self.values
-            .slice(start.to_usize().unwrap(), (end - start).to_usize().unwrap())
+        let end = self.value_offsets()[i + 1].as_usize();
+        let start = self.value_offsets()[i].as_usize();
+        self.values.slice(start, end - start)
     }
 
     /// Returns the offset values in the offsets buffer

arrow-array/src/builder/string_dictionary_builder.rs

@@ -293,9 +293,9 @@ fn get_bytes<'a, K: ArrowNativeType>(values: &'a StringBuilder, key: &K) -> &'a
     let offsets = values.offsets_slice();
     let values = values.values_slice();
 
-    let idx = key.to_usize().unwrap();
-    let end_offset = offsets[idx + 1].to_usize().unwrap();
-    let start_offset = offsets[idx].to_usize().unwrap();
+    let idx = key.as_usize();
+    let end_offset = offsets[idx + 1].as_usize();
+    let start_offset = offsets[idx].as_usize();
 
     &values[start_offset..end_offset]
 }

arrow-buffer/Cargo.toml

@@ -38,7 +38,6 @@ path = "src/lib.rs"
 bench = false
 
 [dependencies]
-num = { version = "0.4", default-features = false, features = ["std"] }
 half = { version = "2.0", default-features = false }
 
 [dev-dependencies]