tustvold commented on code in PR #3622:
URL: https://github.com/apache/arrow-rs/pull/3622#discussion_r1090525144


##########
arrow-select/src/take.rs:
##########
@@ -810,6 +816,70 @@ where
     Ok(DictionaryArray::<T>::from(data))
 }
 
+macro_rules! primitive_run_take {
+    ($t:ty, $o:ty, $indices:ident, $value:ident) => {
+        take_primitive_run_values::<$o, $t>(
+            $indices,
+            as_primitive_array::<$t>($value.values()),
+        )
+    };
+}
+
+/// `take` implementation for run arrays
+///
+/// performs binary search on `run_ends` to get physical indices for the given 
logical indices.
+/// builds output run array by taking values in the input run array at the 
physical indices.
+/// for e.g. an input `RunArray{ run_ends = [2,4,6,8], values=[1,2,1,2] }` and 
`indices=[2,7]`
+/// would be converted to `physical_indices=[1,3]` which will be used to build
+/// output `RunArray{ run_ends=[2], values=[2] }`
+
+pub fn take_run<T, I>(
+    run_array: &RunArray<T>,
+    logical_indices: &PrimitiveArray<I>,
+) -> Result<RunArray<T>, ArrowError>
+where
+    T: RunEndIndexType,
+    T::Native: num::Num,
+    I: ArrowPrimitiveType,
+    I::Native: ToPrimitive,
+{
+    match run_array.data_type() {
+        DataType::RunEndEncoded(_, fl) => {
+            let physical_indices =
+                run_array.get_physical_indices(logical_indices.values())?;
+            downcast_primitive! {
+                fl.data_type() => (primitive_run_take, T, physical_indices, 
run_array),
+                dt => Err(ArrowError::NotYetImplemented(format!("take_run is 
not implemented for {dt:?}")))
+            }
+        }
+        dt => Err(ArrowError::InvalidArgumentError(format!(
+            "Expected DataType::RunEndEncoded found {dt:?}"
+        ))),
+    }
+}
+// Builds a `RunArray` by taking values from given array for the given indices.
+fn take_primitive_run_values<R, V>(

Review Comment:
   Yeah, this wasn't quite what I was suggesting, I'll try to find sometime to 
bash out what I mean later in the week



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