Full Name search query

What I still don't understand, is why this is slower.

That sorting the rows will cost something is obvious. But why so much?
Without ORDER BY rank0... Postgres can just

• pick the first 5 rows it finds and stop fetching rows as soon as it has 5.

  Bitmap Heap Scan on entities ... rows=5 ...

• then compute ts_rank() for just 5 rows.

In the second case, Postgres has to

• fetch all (1495 according to your query plan) rows that qualify.

  Bitmap Heap Scan on entities ... rows=1495 ...

• compute ts_rank() for all of them.
• sort all of them to find the first 5 according to the calculated value.

Try ORDER BY name just to see the cost of computing to_tsquery('english', 'hockey'::text)) for the superfluous rows and how much remains for fetching more rows and sorting.

Thanks to Phil's comment the correct statement looks like this:

SET SERVEROUTPUT ON

DEF username = 'cuser2'

DECLARE

   i_matching NUMBER(1) := null;

BEGIN

   SELECT COUNT (1) INTO i_matching FROM dba_users WHERE username = UPPER('&username');

  DBMS_OUTPUT.put_line(i_matching);

   IF i_matching = 0 THEN

    EXECUTE IMMEDIATE ('create user &username IDENTIFIED BY &username');
    EXECUTE IMMEDIATE ('GRANT CONNECT,RESOURCE,UNLIMITED TABLESPACE TO &username');
    EXECUTE IMMEDIATE ('ALTER USER &username DEFAULT TABLESPACE USERS');
    EXECUTE IMMEDIATE ('ALTER USER &username TEMPORARY TABLESPACE TEMP');

   END IF;

END
;
/