显示“更新”的mysql STATE，而INFO在Show Full Processlist中显示“DELETE”

Question

mysql> SHOW FULL PROCESSLIST;

--------------------------------------------------------
    | Command   |   Time    |   State       |   Info
--------------------------------------------------------
      Execute   |   24      |   updating    |   DELETE FROM table WHERE account_id=? and date=?

How come instead of using UPDATE its using DELETE?

PHP code is this:

$stmt = $mysqli->prepare("INSERT INTO table(account_id,data,date) VALUES(?,?,?) ON DUPLICATE KEY UPDATE data = VALUES(data)");
            $stmt->bind_param('iss', $account_id,$data,$date);
            $stmt->execute();
            $stmt->close();