Fix several CTE related issues

Materialized CTEs did not work properly with INSERT statements

TransformRecursiveCTE was too restrictive

Materialized CTEs were sometimes inlined and thereby duplicated

Fix PIVOT statements after materialized CTE fixes

src/parser/transform/helpers/transform_cte.cpp

@@ -100,9 +100,7 @@ unique_ptr<SelectStatement> Transformer::TransformRecursiveCTE(duckdb_libpgquery
 
 	unique_ptr<SelectStatement> select;
 	switch (stmt.op) {
-	case duckdb_libpgquery::PG_SETOP_UNION:
-	case duckdb_libpgquery::PG_SETOP_EXCEPT:
-	case duckdb_libpgquery::PG_SETOP_INTERSECT: {
+	case duckdb_libpgquery::PG_SETOP_UNION: {
 		select = make_uniq<SelectStatement>();
 		select->node = make_uniq_base<QueryNode, RecursiveCTENode>();
 		auto &result = select->node->Cast<RecursiveCTENode>();
@@ -111,11 +109,10 @@ unique_ptr<SelectStatement> Transformer::TransformRecursiveCTE(duckdb_libpgquery
 		result.left = TransformSelectNode(*PGPointerCast<duckdb_libpgquery::PGSelectStmt>(stmt.larg));
 		result.right = TransformSelectNode(*PGPointerCast<duckdb_libpgquery::PGSelectStmt>(stmt.rarg));
 		result.aliases = info.aliases;
-		if (stmt.op != duckdb_libpgquery::PG_SETOP_UNION) {
-			throw ParserException("Unsupported setop type for recursive CTE: only UNION or UNION ALL are supported");
-		}
 		break;
 	}
+	case duckdb_libpgquery::PG_SETOP_EXCEPT:
+	case duckdb_libpgquery::PG_SETOP_INTERSECT:
 	default:
 		// This CTE is not recursive. Fallback to regular query transformation.
 		return TransformSelect(*PGPointerCast<duckdb_libpgquery::PGSelectStmt>(cte.ctequery));

src/parser/transform/statement/transform_insert.cpp

@@ -42,7 +42,6 @@ unique_ptr<InsertStatement> Transformer::TransformInsert(duckdb_libpgquery::PGIn
 	}
 	if (stmt.selectStmt) {
 		result->select_statement = TransformSelect(stmt.selectStmt, false);
-		result->select_statement->node = TransformMaterializedCTE(std::move(result->select_statement->node));
 	} else {
 		result->default_values = true;
 	}

src/parser/transform/statement/transform_pivot_stmt.cpp

@@ -94,7 +94,7 @@ unique_ptr<SQLStatement> Transformer::GenerateCreateEnumStmt(unique_ptr<CreatePi
 	}
 
 	auto select = make_uniq<SelectStatement>();
-	select->node = std::move(subselect);
+	select->node = TransformMaterializedCTE(std::move(subselect));
 	info->query = std::move(select);
 	info->type = LogicalType::INVALID;
 

src/planner/binder.cpp

@@ -146,7 +146,7 @@ BoundStatement Binder::Bind(SQLStatement &statement) {
 	case StatementType::SELECT_STATEMENT:
 		return Bind(statement.Cast<SelectStatement>());
 	case StatementType::INSERT_STATEMENT:
-		return Bind(statement.Cast<InsertStatement>());
+		return BindWithCTE(statement.Cast<InsertStatement>());
 	case StatementType::COPY_STATEMENT:
 		return Bind(statement.Cast<CopyStatement>(), CopyToType::COPY_TO_FILE);
 	case StatementType::DELETE_STATEMENT:

src/planner/binder/tableref/bind_basetableref.cpp

@@ -129,6 +129,15 @@ unique_ptr<BoundTableRef> Binder::Bind(BaseTableRef &ref) {
 					// retry with next candidate CTE
 					continue;
 				}
+
+				// If we have found a materialized CTE, but no corresponding CTE binding,
+				// something is wrong.
+				if (cte.materialized == CTEMaterialize::CTE_MATERIALIZE_ALWAYS) {
+					throw BinderException(
+					    "There is a WITH item named \"%s\", but it cannot be references from this part of the query.",
+					    ref.table_name);
+				}
+
 				// Move CTE to subquery and bind recursively
 				SubqueryRef subquery(unique_ptr_cast<SQLStatement, SelectStatement>(cte.query->Copy()));
 				subquery.alias = ref.alias.empty() ? ref.table_name : ref.alias;

test/sql/cte/materialized/test_cte_materialized.test

@@ -48,11 +48,9 @@ with cte1 as MATERIALIZED (select 42), cte1 as MATERIALIZED (select 42) select *
 ----
 
 # reference to CTE before its actually defined
-query I
+statement error
 with cte3 as MATERIALIZED (select ref2.j as i from cte1 as ref2), cte1 as MATERIALIZED (Select i as j from a), cte2 as MATERIALIZED (select ref.j+1 as k from cte1 as ref) select * from cte2 union all select * FROM cte3;
 ----
-43
-42
 
 # multiple uses of same CTE
 query II

test/sql/cte/materialized/test_materialized_cte.test

@@ -75,3 +75,12 @@ WITH t(x) AS MATERIALIZED (SELECT 1),
 ----
 2
 1
+
+statement error
+WITH t0(x) AS MATERIALIZED (
+  SELECT x FROM t1
+), t1(x) AS MATERIALIZED (
+  SELECT 1
+)
+SELECT * FROM t0;
+----

test/sql/cte/test_cte.test

@@ -130,3 +130,44 @@ from cte
 where alias2 > 0;
 ----
 1	1
+
+# recursive CTE and a non-recursive CTE with except
+query I
+WITH RECURSIVE t AS (
+  SELECT 1 AS a
+    UNION ALL
+  SELECT a+1
+  FROM t
+  WHERE a < 10
+), s AS (
+  (VALUES (5), (6), (7), (8), (9), (10), (11), (12), (13), (42))
+  EXCEPT
+  TABLE t
+)
+SELECT * FROM s AS _(x) ORDER BY x;
+----
+11
+12
+13
+42
+
+# recursive CTE with except in recursive part (but not as a recursive anchor)
+query I
+WITH RECURSIVE t AS (
+  select 1 as a
+  union all
+  (select a+1
+  from t
+  where a < 10
+  	except
+  SELECT 4)
+), s AS (
+  (values (5), (6), (7))
+  except
+  table t
+)
+SELECT * FROM s AS _(x) ORDER BY x;
+----
+5
+6
+7