Component, Plugin, and Loadable Function Statements table also lists loadable functions installed automatically by server components or plugins. This difference makes  user_defined_functions  preferable to mysql.func  for checking which loadable functions are installed. During the normal startup sequence, the server loads functions registered in the  mysql.func  table. If the server is started with the  --skip-grant-tables  option, functions registered in the table are not loaded and are unavailable. To upgrade the shared library associated with a loadable function, issue a  DROP FUNCTION  statement, upgrade the shared library, and then issue a  CREATE FUNCTION  statement. If you upgrade the shared library first and then use  DROP FUNCTION , the server may unexpectedly shut down. This statement drops the loadable function named  function_name . ( DROP FUNCTION  is also used to drop stored functions; see Section 13.1.29, “DROP PROCEDURE and DROP FUNCTION Statements” .) DROP FUNCTION  is the complement of  CREATE FUNCTION . It requires the  DELETE  privilege for the mysql  system schema because it removes the row from the  mysql.func  system table that registers the function. DROP FUNCTION  also removes the function from the Performance Schema  user_defined_functions table that provides runtime information about installed loadable functions. See Section 27.12.21.8, “The user_defined_functions Table” . During the normal startup sequence, the server loads functions registered in the  mysql.func  table. Because  DROP FUNCTION  removes the  mysql.func  row for the dropped function, the server does not load the function during subsequent restarts. DROP FUNCTION  cannot be used to drop a loadable function that is installed automatically by components or plugins rather than by using  CREATE FUNCTION . Such a function is also dropped automatically, when the component or plugin that installed it is uninstalled. To upgrade the shared library associated with a loadable function, issue a  DROP FUNCTION  statement, upgrade the shared library, and then issue a  CREATE FUNCTION  statement. If you upgrade the shared library first and then use  DROP FUNCTION , the server may unexpectedly shut down. This statement installs one or more components, which become active immediately. A component provides services that are available to the server and other components; see Section 5.5, “MySQL Components” . INSTALL COMPONENT  requires the  INSERT  privilege for the  mysql.component  system table because it adds a row to that table to register the component. Example: 2901 13.7.4.3 INSTALL COMPONENT Statement Note Note 13.7.4.2 DROP FUNCTION Statement for Loadable Functions DROP FUNCTION [IF EXISTS]  function_name INSTALL COMPONENT  component_name  [,  component_name  ] ...