User Defined Functions by Schema in PostgreSQL Database

select 
n.nspname as function_schema,
p.proname as function_name,
l.lanname as function_language,
case when l.lanname = 'internal' 
     then p.prosrc
     else pg_get_functiondef(p.oid)
end as definition,
pg_get_function_arguments(p.oid) as function_arguments,
t.typname as return_type

from      pg_proc      p
left join pg_namespace n on p.pronamespace = n.oid
left join pg_language  l on p.prolang      = l.oid
left join pg_type      t on t.oid          = p.prorettype 

where n.nspname not in ('pg_catalog','information_schema')

order by function_schema, function_name;