Issue Summary

Problem:
When executing a MERGE statement with an async function in the "NOT MATCHED" clause, the query fails with an index out of bounds error.

Steps to Reproduce:

1. Create sequence:

CREATE SEQUENCE test_seq;

2. Create target and source tables:

   CREATE TABLE target_table (id int default nextval(test_seq), name varchar(50), value int);
   CREATE TABLE source_table (id INT, name VARCHAR(50), value INT);

3. Insert data into the source table:

   INSERT INTO source_table (name, value) VALUES ('Item1', 100);

4. Execute the MERGE statement:

   MERGE INTO target_table AS target 
   USING source_table AS source 
   ON target.id = source.id 
   WHEN MATCHED THEN 
      UPDATE SET target.name = source.name, target.value = source.value 
   WHEN NOT MATCHED THEN 
      INSERT (name, value) VALUES (source.name, source.value);

Observed Error:

APIError: QueryFailed: [1104] index out of bounds: the len is 2 but the index is 18446744073709551610

Expected Behavior:
The MERGE statement should execute successfully, inserting or updating records as specified.

Root Cause:
The databend does not properly support async functions (e.g., sequence nextval()) in the NOT MATCHED clause of MERGE.