Hi,
here is a function which is about 8 x faster than the one described in the PostgreSQL SQL Tricks
( http://postgres.cz/wiki/PostgreSQL_SQL_Tricks#Function_for_decoding_of_url_code )
The idea is to handle each encoded/not_encoded parts in bulk rather than spliting on each character.
urldecode_arr:
Seq Scan on lt_referrer (actual time=1.966..17623.979 rows=65717 loops=1)
urldecode:
Seq Scan on lt_referrer (actual time=4.846..144445.292 rows=65717 loops=1)
regards,
Marc Mamin
CREATE OR REPLACE FUNCTION urldecode_arr(url text)
RETURNS text AS
$BODY$
DECLARE ret text;
BEGIN
BEGIN
WITH STR AS (
SELECT
-- array with all non encoded parts, prepend with '' when the string start is encoded
case when $1 ~ '^%[0-9a-fA-F][0-9a-fA-F]'
then array['']
end
|| regexp_split_to_array ($1,'(%[0-9a-fA-F][0-9a-fA-F])+', 'i') plain,
-- array with all encoded parts
array(select (regexp_matches ($1,'((?:%[0-9a-fA-F][0-9a-fA-F])+)', 'gi'))[1]) encoded
)
SELECT string_agg(plain[i] || coalesce( convert_from(decode(replace(encoded[i], '%',''), 'hex'), 'utf8'),''),'')
FROM STR,
(SELECT generate_series(1, array_upper(encoded,1)+2) i FROM STR)blah
INTO ret;
EXCEPTION WHEN OTHERS THEN
raise notice 'failed: %',url;
return $1;
END;
RETURN coalesce(ret,$1); -- when the string has no encoding;
END;
$BODY$
LANGUAGE plpgsql IMMUTABLE STRICT
