fix: preserve approximate percentile arguments with inline ORDER BY

datafusion/sql/src/expr/function.rs

@@ -728,32 +728,16 @@ impl<S: ContextProvider> SqlToRel<'_, S> {
                 // accept a WITHIN GROUP clause.
                 let supports_within_group = fm.supports_within_group_clause();
 
-                // Built-in ordered-set aggregates must also support WITHIN GROUP
-                let is_builtin_ordered_set = matches!(
-                    name.as_str(),
-                    "percentile_cont"
-                        | "quantile_cont"
-                        | "approx_percentile_cont"
-                        | "approx_percentile_cont_with_weight"
-                );
-
-                let supports_within_group =
-                    supports_within_group || is_builtin_ordered_set;
-
                 let mut within_group = within_group;
                 let mut order_by = order_by;
 
-                if supports_within_group
+                let is_inline_order_by = supports_within_group
                     && within_group.is_empty()
-                    && !order_by.is_empty()
-                {
+                    && !order_by.is_empty();
+
+                if is_inline_order_by {
                     // Inline ORDER BY syntax:
                     // quantile_cont(value, percentile ORDER BY value)
-                    if args.len() >= 2 {
-                        args.remove(0);
-                        arg_names.remove(0);
-                    }
-
                     within_group = order_by;
                     order_by = vec![];
                 }
@@ -781,6 +765,15 @@ impl<S: ContextProvider> SqlToRel<'_, S> {
                             );
                         }
 
+                        // Remove the ordered value only when it is explicitly repeated.
+                        // This ensures these are equivalent:
+                        //   approx_percentile_cont(c3, 0.95, 200 ORDER BY c3)
+                        //   approx_percentile_cont(0.95, 200 ORDER BY c3)
+                        if is_inline_order_by && args.first() == Some(&sorts[0].expr) {
+                            args.remove(0);
+                            arg_names.remove(0);
+                        }
+
                         // Prepend ordered value expression to args
                         let value_expr = sorts[0].expr.clone();
                         arg_names = std::iter::once(None).chain(arg_names).collect();

datafusion/sqllogictest/test_files/aggregate.slt

@@ -2733,6 +2733,26 @@ c 122
 d 123.15
 e 110.266666666667
 
+# inline ORDER BY preserves percentile and centroids arguments
+query TR
+SELECT c1, approx_percentile_cont(0.95, 200 ORDER BY c3) AS c3_p95 FROM aggregate_test_100 GROUP BY c1 ORDER BY c1
+----
+a 73.55
+b 68
+c 122.5
+d 124.2
+e 115.6
+
+# inline ORDER BY preserves the weight argument
+query TR
+SELECT c1, approx_percentile_cont_with_weight(1, 0.95 ORDER BY c3) AS c3_p95 FROM aggregate_test_100 GROUP BY c1 ORDER BY c1
+----
+a 73.55
+b 68
+c 122.5
+d 124.2
+e 115.6
+
 # csv_query_sum_crossjoin
 query TTI
 SELECT a.c1, b.c1, SUM(a.c2) FROM aggregate_test_100 as a CROSS JOIN aggregate_test_100 as b GROUP BY a.c1, b.c1 ORDER BY a.c1, b.c1