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Re: reverse strpos?

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On Mon, Nov 12, 2007 at 05:19:25PM +0100, A. Kretschmer wrote:
> am  Mon, dem 12.11.2007, um 10:54:53 -0500 mailte Gauthier, Dave folgendes:
> > Is there a function that?ll return the position of the last
> > occurance of a char in a string? 
> > 
> > For Example, in the string ?abc/def/ghi? I want the position of
> > the 2^nd ?/?.
> 
> write a function to revert the string and use strpos().
> 
> create or replace function rev(varchar) returns varchar as $$
> declare
>         _temp varchar;
>         _count int;
> begin
>         _temp := '';
>         for _count in reverse length($1)..1 loop
>                 _temp := _temp || substring($1 from _count for 1);
>         end loop;
>         return _temp;
> end;
> $$ language plpgsql immutable;
> 
> 
> Andreas

PL/Perl might be easier:

CREATE OR REPLACE FUNCTION rev(TEXT)
RETURNS TEXT
IMMUTABLE
LANGUAGE plperl
AS $$
return reverse($_[0]);
$$;

You could also write wrappers around perl functions if you're taking
that route.

If you want to guarantee the thing runs on any modern Postgres
instance--one where you don't control the environment at all--you
could do:

CREATE OR REPLACE FUNCTION rev(TEXT)
RETURNS TEXT
IMMUTABLE
LANGUAGE SQL
AS $$
SELECT array_to_string(
    ARRAY(
        SELECT substr($1,i,1)
        FROM generate_series(length($1),1,-1) AS i
    ),
    ''
);
$$;

Cheers,
David.
-- 
David Fetter <david@xxxxxxxxxx> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david.fetter@xxxxxxxxx

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