fix: filter push down union in r cte

src/query/sql/src/planner/optimizer/rule/rewrite/rule_push_down_filter_union.rs

@@ -72,6 +72,11 @@ impl Rule for RulePushDownFilterUnion {
         let filter: Filter = s_expr.plan().clone().try_into()?;
         let union_s_expr = s_expr.child(0)?;
         let union: UnionAll = union_s_expr.plan().clone().try_into()?;
+        if !union.cte_scan_names.is_empty() {
+            // If the union has cte scan names, it's not allowed to push down filter.
+            state.add_result(s_expr.clone());
+            return Ok(());
+        }
 
         // Create a filter which matches union's right child.
         let index_pairs: HashMap<IndexType, IndexType> = union

tests/sqllogictests/suites/query/cte/r_cte_union_all.test

@@ -76,3 +76,43 @@ SELECT * FROM t;
 7
 8
 9
+
+# bug: https://github.com/databendlabs/databend/issues/17027
+statement ok
+CREATE or replace TABLE parent_child
+(
+  parent VARCHAR(30),
+  child VARCHAR(30)
+);
+
+statement ok
+INSERT INTO parent_child
+VALUES ('Org','Org'),('Org','Global'),('Global','North'),
+('Global','South'),('Global','East'),('Global','West'),
+('Global','Org detail'),('North','North East'),('North','North West');
+
+query I
+WITH RECURSIVE tree_values
+    (parent, child)
+AS (
+    SELECT parent, child
+    FROM parent_child
+    WHERE parent = child
+    UNION ALL
+    SELECT c.parent, c.child
+    FROM parent_child c
+    INNER JOIN tree_values p
+    ON p.child = c.parent
+    WHERE c.parent != c.child
+)
+select parent, child from tree_values
+where parent = 'Global';
+----
+Global East
+Global North
+Global Org detail
+Global South
+Global West
+
+statement ok
+drop table parent_child;