Pynject is a tool to automatize data dumping AFTER you found some SQL injection with a visible UNION, for instance with tools like sqlibf.
Once you have the union injection, just give it to Pynject and it will fetch any data you want from the db, in a multithreaded fashion, so it's incredibly FAST compared to other tools!!!
For more info, see:
(gdb) disass m(y_br)ain