urlencode with only built-in functions

Question

Without using plpgsql, I\'m trying to urlencode a given text within a pgsql SELECT statement.

The problem with this approach:

select regexp_replace(\         


        

Answer 1

Here's a function I wrote that handles encoding using built in functions while preserving the readability of the URL.

Regex matches to capture pairs of (optional) safe characters and (at most one) non-safe character. Nested selects allow those pairs to be encoded and re-combined returning a fully encoded string.

I've run through a test suite with all sorts of permutations (leading/trailing/only/repeated encoded characters and thus far it seems to encode correctly.

The safe special characters are _ ~ . - and /. My inclusion of "/" on that list is probably non-standard, but fits the use case I have where the input text may be a path and I want that to remain.

CREATE OR REPLACE FUNCTION oseberg.encode_uri(input text)
  RETURNS text
  LANGUAGE plpgsql
  IMMUTABLE STRICT
AS $function$
DECLARE
  parsed text;
  safePattern text;
BEGIN
  safePattern = 'a-zA-Z0-9_~/\-\.';
  IF input ~ ('[^' || safePattern || ']') THEN
    SELECT STRING_AGG(fragment, '')
    INTO parsed
    FROM (
      SELECT prefix || encoded AS fragment
      FROM (
        SELECT COALESCE(match[1], '') AS prefix,
               COALESCE('%' || encode(match[2]::bytea, 'hex'), '') AS encoded
        FROM (
          SELECT regexp_matches(
            input,
            '([' || safePattern || ']*)([^' || safePattern || '])?',
            'g') AS match
        ) matches
      ) parsed
    ) fragments;
    RETURN parsed;
  ELSE
    RETURN input;
  END IF;
END;
$function$