fix(rust, python): use row-encoded for struct::is_sorted (#10129)

polars/polars-ops/src/series/ops/various.rs

@@ -1,5 +1,7 @@
 #[cfg(feature = "hash")]
 use polars_core::export::ahash;
+#[cfg(feature = "dtype-struct")]
+use polars_core::prelude::sort::arg_sort_multiple::_get_rows_encoded_ca;
 use polars_core::prelude::*;
 use polars_core::series::IsSorted;
 
@@ -42,6 +44,14 @@ pub trait SeriesMethods: SeriesSealed {
     fn is_sorted(&self, options: SortOptions) -> PolarsResult<bool> {
         let s = self.as_series();
 
+        // for struct types we row-encode and recurse
+        #[cfg(feature = "dtype-struct")]
+        if matches!(s.dtype(), DataType::Struct(_)) {
+            let encoded =
+                _get_rows_encoded_ca("", &[s.clone()], &[options.descending], options.nulls_last)?;
+            return encoded.into_series().is_sorted(options);
+        }
+
         // fast paths
         if (options.descending
             && options.nulls_last
@@ -70,27 +80,12 @@ pub trait SeriesMethods: SeriesSealed {
         // Compare adjacent elements with no-copy slices that don't include any nulls
         let offset = !options.nulls_last as i64 * nc as i64;
         let (s1, s2) = (s.slice(offset, slen), s.slice(offset + 1, slen));
-        let cmp_op = match options.descending {
-            true => Series::gt_eq,
-            false => Series::lt_eq,
+        let cmp_op = if options.descending {
+            Series::gt_eq
+        } else {
+            Series::lt_eq
         };
-        match s.dtype() {
-            // For structs compare per-field. We don't have to check any types or field names though
-            // since we're just comparing two offset slices of the same Series. The loop is to both
-            // short-circuit on false and propagate errors. Maybe there's a way with iterators?
-            #[cfg(feature = "dtype-struct")]
-            DataType::Struct(_) => {
-                let mut struct_cmp = true;
-                for (l, r) in s1.struct_()?.fields().iter().zip(s2.struct_()?.fields()) {
-                    struct_cmp &= cmp_op(l, r)?.all();
-                    if !struct_cmp {
-                        break;
-                    }
-                }
-                Ok(struct_cmp)
-            }
-            _ => Ok(cmp_op(&s1, &s2)?.all()),
-        }
+        Ok(cmp_op(&s1, &s2)?.all())
     }
 }