Postgresql DROP TABLE doesn't work

What is the output of

SELECT *
  FROM pg_locks l
  JOIN pg_class t ON l.relation = t.oid AND t.relkind = 'r'
 WHERE t.relname = 'Bill';

It might be that there're other sessions using your table in parallel and you cannot obtain Access Exclusive lock to drop it.

Just do

SELECT pid, relname
FROM pg_locks l
JOIN pg_class t ON l.relation = t.oid AND t.relkind = 'r'
WHERE t.relname = 'Bill';

And then kill every pid by

kill 1234

Where 1234 is your actual pid from query results.

You can pipe it all together like this (so you don't have to copy-paste every pid manually):

psql -c "SELECT pid FROM pg_locks l 
    JOIN pg_class t ON l.relation = t.oid AND t.relkind = 'r' 
    WHERE t.relname = 'Bill';" | tail -n +3 | head -n -2 | xargs kill

So I was hitting my head against the wall for some hours trying to solve the same issue, and here is the solution that worked for me:

Check if PostgreSQL has a pending prepared transaction that's never been committed or rolled back:

SELECT database, gid FROM pg_prepared_xacts;

If you get a result, then for each transaction gid you must execute a ROLLBACK from the database having the problem:

ROLLBACK PREPARED 'the_gid';

For further information, click here.