Cquirrel: continuous query processing over acyclic relational schemas

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.