Merge pull request #20610 from ucasFL/fix-union-distinct-limit

fix subquery with limit

src/Interpreters/InterpreterSelectQuery.cpp

@@ -784,9 +784,22 @@ static bool hasWithTotalsInAnySubqueryInFromClause(const ASTSelectQuery & query)
     {
         if (const auto * ast_union = query_table->as<ASTSelectWithUnionQuery>())
         {
+            /// NOTE: Child of subquery can be ASTSelectWithUnionQuery or ASTSelectQuery,
+            /// and after normalization, the height of the AST tree is at most 2
             for (const auto & elem : ast_union->list_of_selects->children)
-                if (hasWithTotalsInAnySubqueryInFromClause(elem->as<ASTSelectQuery &>()))
-                    return true;
+            {
+                if (const auto * child_union = elem->as<ASTSelectWithUnionQuery>())
+                {
+                    for (const auto & child_elem : child_union->list_of_selects->children)
+                        if (hasWithTotalsInAnySubqueryInFromClause(child_elem->as<ASTSelectQuery &>()))
+                            return true;
+                }
+                else
+                {
+                    if (hasWithTotalsInAnySubqueryInFromClause(elem->as<ASTSelectQuery &>()))
+                        return true;
+                }
+            }
         }
     }
 

tests/queries/0_stateless/01720_union_distinct_with_limit.reference

+1

tests/queries/0_stateless/01720_union_distinct_with_limit.sql

+SELECT x
+FROM
+(
+    SELECT 1 AS x
+    UNION DISTINCT
+    SELECT 1
+)
+LIMIT 1;