From: | Marti Raudsepp <marti(at)juffo(dot)org> |
---|---|
To: | Edson Carlos Ericksson Richter <richter(at)simkorp(dot)com(dot)br> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Does postgresql 9.0.4 use index on PREFIX%SUFFIX queries? |
Date: | 2011-09-27 00:26:07 |
Message-ID: | CABRT9RDxHKCxrq8wboHnikpF-CGgkteJWdw3Q2_kXFEdP4prTw@mail.gmail.com |
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Lists: | pgsql-general |
On Tue, Sep 27, 2011 at 01:43, Edson Carlos Ericksson Richter
<richter(at)simkorp(dot)com(dot)br> wrote:
>> create index on foobar (txt text_pattern_ops); create index on foobar
>> (reverse(txt) text_pattern_ops);
>
> I got the following error:
>
> ERROR: function reverse(text) does not exist
> Hint: No function matches the given name and argument types. You might need to add explicit type casts.
Ah, the reverse() function is not included with PostgreSQL 9.0 yet.
This is what I use:
CREATE FUNCTION reverse(input text) RETURNS text
LANGUAGE plpgsql IMMUTABLE STRICT AS $$
DECLARE
result text = '';
i int;
BEGIN
FOR i IN 1..length(input) BY 2 LOOP
result = substr(input,i+1,1) || substr(input,i,1) || result;
END LOOP;
RETURN result;
END$$;
Regards,
Marti
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