How to get distinct array elements with postgres?

Question

I have an array with duplicate values in postgres. For example:

SELECT cardinality(string_to_array('1,2,3,4,4', ',')::int[]) as foo
=> "foo"=>"5"

I would like to get unique elements, for example:

SELECT cardinality(uniq(string_to_array('1,2,3,4,4', ',')::int[])) as foo
=> -- No function matches the given name and argument types. You might need to add explicit type casts.

Can I get unique elements of an array in postgres without using UNNEST ?

Answer 1

I prefer this syntax (about 5% faster)

create or replace function public.array_unique(arr anyarray)
returns anyarray as $body$
    select array( select distinct unnest($1) )
$body$ language 'sql';

using:

select array_unique(ARRAY['1','2','3','4','4']);