fix: null in array_agg with DISTINCT and IGNORE

datafusion/optimizer/src/single_distinct_to_groupby.rs

@@ -184,7 +184,11 @@ impl OptimizerRule for SingleDistinctToGroupBy {
                             func,
                             params:
                                 AggregateFunctionParams {
-                                    mut args, distinct, ..
+                                    mut args,
+                                    distinct,
+                                    filter,
+                                    order_by,
+                                    null_treatment,
                                 },
                         }) => {
                             if distinct {
@@ -204,9 +208,9 @@ impl OptimizerRule for SingleDistinctToGroupBy {
                                     func,
                                     vec![col(SINGLE_DISTINCT_ALIAS)],
                                     false, // intentional to remove distinct here
-                                    None,
-                                    vec![],
-                                    None,
+                                    filter,
+                                    order_by,
+                                    null_treatment,
                                 )))
                                 // if the aggregate function is not distinct, we need to rewrite it like two phase aggregation
                             } else {
@@ -217,9 +221,9 @@ impl OptimizerRule for SingleDistinctToGroupBy {
                                         Arc::clone(&func),
                                         args,
                                         false,
-                                        None,
-                                        vec![],
-                                        None,
+                                        filter,
+                                        order_by,
+                                        null_treatment,
                                     ))
                                     .alias(&alias_str),
                                 );

datafusion/sqllogictest/test_files/aggregate.slt

@@ -379,6 +379,59 @@ select array_sort(c1), array_sort(c2) from (
 statement ok
 drop table array_agg_distinct_list_table;
 
+# Test array_agg with DISTINCT and IGNORE NULLS (regression test for issue #19735)
+query ?
+SELECT array_sort(ARRAY_AGG(DISTINCT x IGNORE NULLS)) as result
+FROM (VALUES (1), (2), (NULL), (2), (NULL), (1)) AS t(x);
+----
+[1, 2]
+
+# Test that non-DISTINCT aggregates also preserve IGNORE NULLS when mixed with DISTINCT
+# This tests the two-phase aggregation rewrite in SingleDistinctToGroupBy
+query I?
+SELECT
+  COUNT(DISTINCT x) as distinct_count,
+  array_sort(ARRAY_AGG(y IGNORE NULLS)) as y_agg
+FROM (VALUES
+  (1, 10),
+  (1, 20),
+  (2, 30),
+  (3, NULL),
+  (3, 40),
+  (NULL, 50)
+) AS t(x, y)
+----
+3 [10, 20, 30, 40, 50]
+
+# Test that FILTER clause is preserved in two-phase aggregation rewrite
+query II
+SELECT
+  COUNT(DISTINCT x) as distinct_count,
+  SUM(y) FILTER (WHERE y > 15) as filtered_sum
+FROM (VALUES
+  (1, 10),
+  (1, 20),
+  (2, 5),
+  (2, 30),
+  (3, 25)
+) AS t(x, y)
+----
+3 75
+
+# Test that ORDER BY is preserved in two-phase aggregation rewrite
+query I?
+SELECT
+  COUNT(DISTINCT x) as distinct_count,
+  ARRAY_AGG(y ORDER BY y DESC) as ordered_agg
+FROM (VALUES
+  (1, 10),
+  (1, 30),
+  (2, 20),
+  (2, 40)
+) AS t(x, y)
+----
+2 [40, 30, 20, 10]
+
 statement error This feature is not implemented: Calling array_agg: LIMIT not supported in function arguments: 1
 SELECT array_agg(c13 LIMIT 1) FROM aggregate_test_100