Executing show variable in prepare mode returns an error result

[keeplearning20221]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

String sql_show = "show variables like 'tidb_snapshot';";
PreparedStatement pstmt_show = conn.prepareStatement(sql_show);
ResultSet res = pstmt_show.executeQuery();
if (res.next()) {
String id = res.getString("Value") ;
System.out.println("Snapshot:" + id);

                    }

2. What did you expect to see? (Required)

Snapshot:434736612009312258 or Snapshot:

3. What did you see instead (Required)

Snapshot:OFF

4. What is your TiDB version? (Required)

Release Version: v6.1.0