[GitHub] [arrow-rs] tustvold commented on a diff in pull request #3185: Simplify dyn comparator and make NaN ordering consistent (#1941)

[GitBox <gi...@apache.org>]

tustvold commented on code in PR #3185:
URL: https://github.com/apache/arrow-rs/pull/3185#discussion_r1031761178


##########
arrow/src/array/ord.rs:
##########
@@ -20,140 +20,43 @@
 use std::cmp::Ordering;
 
 use crate::array::*;
-use crate::datatypes::TimeUnit;
 use crate::datatypes::*;
 use crate::error::{ArrowError, Result};
 
-use num::Float;
+use arrow_array::{downcast_integer, downcast_primitive};
 
-/// Compare the values at two arbitrary indices in two arrays.
-pub type DynComparator = Box<dyn Fn(usize, usize) -> Ordering + Send + Sync>;
-
-/// compares two floats, placing NaNs at last
-fn cmp_nans_last<T: Float>(a: &T, b: &T) -> Ordering {
-    match (a.is_nan(), b.is_nan()) {
-        (true, true) => Ordering::Equal,
-        (true, false) => Ordering::Greater,
-        (false, true) => Ordering::Less,
-        _ => a.partial_cmp(b).unwrap(),
-    }
+macro_rules! primitive_helper {
+    ($t:ty, $left:ident, $right:ident) => {{
+        let left = PrimitiveArray::<$t>::from($left.data().clone());
+        let right = PrimitiveArray::<$t>::from($right.data().clone());
+        Box::new(move |i, j| left.value(i).compare(right.value(j)))
+    }};
 }
 
-fn compare_primitives<T: ArrowPrimitiveType>(
-    left: &dyn Array,
-    right: &dyn Array,
-) -> DynComparator
-where
-    T::Native: Ord,
-{
-    let left: PrimitiveArray<T> = PrimitiveArray::from(left.data().clone());
-    let right: PrimitiveArray<T> = PrimitiveArray::from(right.data().clone());
-    Box::new(move |i, j| left.value(i).cmp(&right.value(j)))
+macro_rules! array_helper {
+    ($t:ty, $left:ident, $right:ident) => {{
+        let left = <$t>::from($left.data().clone());
+        let right = <$t>::from($right.data().clone());
+        Box::new(move |i, j| left.value(i).cmp(&right.value(j)))
+    }};
 }
 
-fn compare_boolean(left: &dyn Array, right: &dyn Array) -> DynComparator {
-    let left: BooleanArray = BooleanArray::from(left.data().clone());
-    let right: BooleanArray = BooleanArray::from(right.data().clone());
-
-    Box::new(move |i, j| left.value(i).cmp(&right.value(j)))
+macro_rules! dictionary_helper {
+    ($t:ty, $build_compare:ident, $left:ident, $right:ident) => {{
+        let left = DictionaryArray::<$t>::from($left.data().clone());
+        let right = DictionaryArray::<$t>::from($right.data().clone());
+        let compare = $build_compare(left.values().as_ref(), right.values().as_ref())?;
+
+        Box::new(move |i, j| {
+            let left_v = left.keys().value(i);
+            let right_v = right.keys().value(j);
+            compare(left_v as _, right_v as _)

Review Comment:
   This does add an additional dynamic dispatch to dictionary comparisons, I think this is worth the tradeoff of saving significant amounts of compilation time and codegen. Ultimately if people want efficient dynamic comparisons, they should use the row format



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