Column-wise autocomplete - postgresql

Question

I have a table in a PostgreSQL database with four columns that contain increasingly more detailed information (think state->city->street->number), along with a column where everything is concatenated according to some simple formatting rules. Example:
| kommun | trakt | block | enhet | beteckning |
| Mora | Gislövs Läge | 9 | 16 | Mora Gislövs Läge 9:16 |
| Mora | Gisslaved | * | 8 | Mora Gisslaved 8 |
| Mora | Gisslaved | * | 9 | Mora Gisslaved 9 |
| Lilla Edet | Sanda | GA | 1 | Lilla Edet Sanda GA:1 |
A web service uses this table to implement a word-wise autocomplete, where the user gets input suggestions as they drill down. An input of mora gis will result in
["Mora Gislövs", "Mora Gisslaved"]
Currently, this is done by splitting the concatenated column by word in this query:
select distinct trim(substring(beteckning from '(^(\S+\s?){NUMPARTS})')) as bet
from beteckning_ac
where upper(beteckning) like upper('mora gis%')
order by bet
Where NUMPARTS is the number of words in the input - 2 in this case.
Now I want the autocomplete to be done column-wise rather than word-wise, so mora gis would now result in this instead:
["Mora Gislövs Läge", "Mora Gisslaved"]
Since the first two columns can contain an arbitrary number of words, I can no longer use the input to determine how many columns to include in the response. Is there a way to do this, or have I maybe gone about this autocomplete business all wrong?

Answer 1

CREATE OR REPLACE FUNCTION get_auto(text)
--$1 is here your input
RETURNS setof text
LANGUAGE plpgsql
AS $function$
declare
NUMPARTS int := array_length(regexp_split_to_array($1,' '), 1);
begin
return query
select
case
when (NUMPARTS = 1) then kommun
when (NUMPARTS = 2) then kommun||' '||trakt
when (NUMPARTS = 3) then kommun||' '||trakt||' '||block
when (NUMPARTS = 4) then kommun||' '||trakt||' '||block||' '||enhet
--alter if you want to
end
from
auto_complete --your tablename here
where
beteckning like $1||'%';
end;
$function$;