How to replace multiple special characters in Postgres 9.5

Question

I have a table containing a list of name which might contain special character:

id   name
1    Johän
2    Jürgen
3    Janna
4    Üdyr
...

Is there a function that replaces each character for another specific one? (Not necessarily an unaccented one). Something like this:

SELECT id, function('ä,ü',name,'ae,ue');
Result:

    id   name
    1    Johaen
    2    Juergen
    3    Janna
    4    UEdyr
    ...

Answer 1

No, there are no this function. Probably is not to hard to write optimized C extension what does it. But C language is not necessary always. You can try SQL or PLpgSQL function:

CREATE OR REPLACE FUNCTION xx(text, text[], text[])
RETURNS text AS $$
   SELECT string_agg(coalesce($3[array_position($2, c)],c),'')
      FROM regexp_split_to_table($1,'') g(c)
$$ LANGUAGE sql;

postgres=# select xx('Jürgen', ARRAY['ä','ü'], ARRAY['ae','ue']);
┌─────────┐
│   xx    │
╞═════════╡
│ Juergen │
└─────────┘
(1 row)

On my comp it does 6000 transformation under 200ms (but I have developer build of PostgreSQL - it is slower).