We will demonstrate Cquirrel, a continuous query processing engine built on top of Flink. Cquirrel assumes a relational schema where the foreign-key constraints form a directed acyclic graph, and supports any selection-projection-join-aggregation query where all join conditions are between a primary key and a foreign key. It allows arbitrary updates to any of the relations, and outputs the deltas in the query answers in real-time. It provides much better support for multi-way joins than the native join operator in Flink. Meanwhile, it offers better performance, scalability, and fault tolerance than other continuous query processing engines.

Big-data frameworks (e.g., Spark) enable computations on tremendous data records generated by third parties, causing various security and reliability problems such as information leakage and programming bugs. Existing systems for big-data security (e.g., Titian) track data transformations in a record level, so they are imprecise and too coarse-grained for these problems. For instance, when we ran Titian to drill down input records that produced a buggy output record, Titian reported 3 to 9 orders of magnitude more input records than the actual ones. Information Flow Tracking (IFT) is a conventional approach for precise information control. However, extant IFT systems are neither efficient nor complete for big-data frameworks, because theses frameworks are data-intensive, and data flowing across hosts is often ignored by IFT.