Vertica provides ALTER statements for each type of user-defined extension. Each ALTER statement modifies the metadata of a user-defined function in the Vertica catalog:

ALTER statement Extension
ALTER FUNCTION (Scalar) User-defined scalar functions (UDSFs)
ALTER AGGREGATE FUNCTION User-defined aggregate functions (UDAFs)
ALTER ANALYTIC FUNCTION User-defined analytic functions (UDAnF)
ALTER TRANSFORM FUNCTION User-defined transform functions (UDTFs)
ALTER statements for user-defined load:
ALTER SOURCE Load source functions
ALTER FILTER Load filter functions
ALTER PARSER Load parser functions

Vertica also provides ALTER FUNCTION (SQL), which modifies the metadata of a user-defined SQL function.