Index for speeding up sorting by boolean, timestamp
Try creating the following index, running ANALYZE cms_news, and posting the EXPLAIN ANALYZE plan again

CREATE INDEX cms_news_flash_ts_idx ON cms_news ( flash desc, timestamp desc );


Tip: You can post your EXPLAIN ANALYZE plans to http://explain.depesz.com/ and post the link back here. I've found it to be a pretty helpful tool over the years.