Comment by Frank Heikens on What should I do so returning 200 rows is at least as fast as returning 1000 rows when performing partial match queries on an indexed column?

Could you please use explain(analyze, verbose, buffers, settings) to get the whole picture? To me, it looks like the first query plan is not the best plan. And in this case, that is slower than the index scan on a larger set. It all looks like the wrong database configuration and a rather small test set.