Check here for Presto details and documentation; for another perspective, see Facebook open sources its SQL-on-Hadoop engine, and the web rejoices (Gigaom)
"In Fall 2012, a small team in the Facebook Data Infrastructure group set out to solve this problem for our warehouse users. We evaluated a few external projects, but they were either too nascent or did not meet our requirements for flexibility and scale. So we decided to build Presto, a new interactive query system that could operate fast at petabyte scale.Presto: Interacting with petabytes of data at Facebook
In this post, we will briefly describe the architecture of Presto, its current status, and future roadmap.
Presto is a distributed SQL query engine optimized for ad-hoc analysis at interactive speed. It supports standard ANSI SQL, including complex queries, aggregations, joins, and window functions."