planner: fix pointer dereference

node/engine/planner/logical/planner.go

@@ -1573,6 +1573,10 @@ func (s *scopeContext) exprWithAggRewrite(node parse.Expression, currentRel *Rel
 			// might be in the outer relation, correlated
 			field, err = s.OuterRelation.Search(node.Table, node.Column)
 			if errors.Is(err, ErrColumnNotFound) {
+				if s.preGroupRelation == nil {
+					return nil, nil, false, fmt.Errorf(`%w: unknown column reference "%s"`, ErrColumnNotFound, node.String())
+				}
+
 				// if not found, see if it is in the relation but not grouped
 				field, err2 := s.preGroupRelation.Search(node.Table, node.Column)
 				// if the column exist in the outer relation, then it might be part of an expression
@@ -1942,7 +1946,7 @@ func (s *scopeContext) exprWithAggRewrite(node parse.Expression, currentRel *Rel
 			}
 		}
 
-		return subqExpr, rel.Fields[0], shouldRewrite, nil
+		return cast(subqExpr, rel.Fields[0])
 	}
 }
 

node/engine/planner/logical/planner_test.go

@@ -616,6 +616,27 @@ func Test_Planner(t *testing.T) {
 				"    └─Filter: r.n < 10\n" +
 				"      └─Scan Table: r [cte]\n",
 		},
+		{
+			// this caused a nil pointer dereference.
+			// It is an illegal query, but it should not crash the planner.
+			name: "inserting a cte",
+			sql: `with a as (select 1)
+			INSERT INTO users VALUES ('123e4567-e89b-12d3-a456-426614174000'::uuid, 'satoshi', a)`,
+			err: logical.ErrColumnNotFound,
+		},
+		{
+			// this is a regression test for a previous uncaught type case
+			name: "subquery type cast",
+			sql:  `select * from users where age = (select sum(age) from users)::int8`,
+			wt: "Return: id [uuid], name [text], age [int8]\n" +
+				"└─Project: users.id; users.name; users.age\n" +
+				"  └─Filter: users.age = [subquery (scalar) (subplan_id=0) (uncorrelated)]::int8\n" +
+				"    └─Scan Table: users [physical]\n" +
+				"Subplan [subquery] [id=0]\n" +
+				"└─Project: {#ref(A)}\n" +
+				"  └─Aggregate: {#ref(A) = sum(users.age)}\n" +
+				"    └─Scan Table: users [physical]\n",
+		},
 	}
 
 	for _, test := range tests {