strip_md.sql

-- strip_md(text) - strips markdown from text
-- (c) 2014 Felix Buenemann https://github.com/felixbuenemann
-- License: Public Domain
CREATE OR REPLACE FUNCTION strip_md(input text) RETURNS text AS $$
BEGIN
  -- strip html tags
  input := regexp_replace(input, '<[^>]+>', '', 'g');
  -- strip list leaders and blockquotes
  input := regexp_replace(input, '^([\s]*)([\*\-\+]|\d\.|>)\s+', '\1', 'ng');
  -- strip setext header underlines
  input := regexp_replace(input, '^[=\-]{2,}\s*$', '', 'ng');
  -- strip atx header hash chars
  input := regexp_replace(input, '^#{1,6}\s*', '', 'ng');
  -- strip embeds (images)
  input := regexp_replace(input, '\!\[([^\[]+)\](\[\]|\([^\)]+\))', '', 'g');
  -- strip links, keep body
  input := regexp_replace(input, '\[([^\[]+)\](\[\]|\([^\)]+\))', '\1', 'g');
  -- strip link definitions
  input := regexp_replace(input, '\[([^\[]+)\]:\([^\)]+\)', '\1', 'g');
  -- strip strong
  input := regexp_replace(input, '(\*\*)(\S.*?\S)\1', '\2', 'g');
  input := regexp_replace(input, '(__)(\S.*?\S)\1', '\2', 'g');
  -- strip emphasis
  input := regexp_replace(input, '(\*)(\S.*?\S)\1', '\2', 'g');
  input := regexp_replace(input, '(_)(\S.*?\S)\1', '\2', 'g');
  -- strip strikethrough
  input := regexp_replace(input, '(~~)(\S.*?\S)\1', '\2', 'g');
  -- strip quotes
  input := regexp_replace(input, ':"(.*?)":', '\1', 'g');
  -- strip inline code
  input := regexp_replace(input, '`(.*?)`', '\1', 'g');
  -- strip fenced code blocks
  input = regexp_replace(input, '(`{3,})(.*?)\1', '\2', 'g');
  -- strip horizontal rules
  input := regexp_replace(input, '^((- ?){3,}|(\* ?){3,})\s*$', '', 'ng');
  -- remove windows style returns
  input := regexp_replace(input, '\r', '', 'g');
  -- consolidate newlines
  input := regexp_replace(input, '\n{2,}', E'\n\n', 'g');

  RETURN input;
END;
$$ LANGUAGE plpgsql IMMUTABLE;

This currently removes the url from links. It can easily be changed by modifying the regex on line 17.