在postgres函数中使用if

Question

这是用于注册的函数，但是当使用此函数时，输入的数据不会进入数据库，如果输入的新数据无法输入查询插入，则查询将一直只读，直到“用户名已存在”

    DECLARE
  headers JSONB;
  body JSONB;

  var_username VARCHAR;
  var_password VARCHAR;
  var_full_name VARCHAR;
  var_email VARCHAR;
  var_company VARCHAR;

  var_id BIGINT;
BEGIN
  headers = request->'headers';
  body = request->'body';

  var_username = body->>'username';
  var_password = body->>'password'; 
  var_full_name = body->>'full_name';
  var_email = body->>'email';
  var_company = body->>'company';

    IF EXISTS(SELECT id FROM sso.users WHERE username = var_username) THEN
    RETURN jsonb_build_object(
        'success' , false,
        'message', 'Username already exists'
    );
  END IF;

  INSERT INTO sso.users(username, email, password, full_name, company) 
  VALUES (var_username, var_email, var_password, var_full_name, var_company) 
  RETURNING id INTO var_id;


  RETURN(
    'success', true,
    'token', var_id::varchar
  );
END;