Yes.. I will write an article on this but for now you control this using the following parameter:
If you decrease it, you get more reducers.
If you increase it, you get less. By default it is 1 GB.
Try starting from 256MB and see the amount of reducers created.
Link to article
In addition to what Ancil wrote you can also simply set the number of reducers as well:
The Hive guys don't like it too much because it can obviously result in bad performance if you don't know what you are doing. But in edge cases ... I use it for example to determine the number of ORC files during big loads.