Streaming SQL Foundations: Why I ❤ Streams+Tables

What does it mean to execute robust streaming queries in SQL? What is the relationship of streaming queries to classic relational queries? Are streams and tables the same thing conceptually, or different? And how does all of this relate to the programmatic frameworks like we’re all familiar with? This talk will address all of those questions in two parts.

First, we’ll explore the relationship between the Beam Model (as described in The Dataflow Model paper and the Streaming 101 and Streaming 102 blog posts) and stream & table theory (as popularized by Martin Kleppmann and Jay Kreps, amongst others, but essentially originating out of the database world). It turns out that stream & table theory does an illuminating job of describing the low-level concepts that underlie the Beam Model.

Second, we’ll apply our clear understanding of that relationship towards explaining what is required to provide robust stream processing support in SQL. We’ll discuss concrete efforts that have been made in this area by the Apache Beam, Calcite, and Flink communities, compare to other offerings such as Apache Kafka’s KSQL and Apache Spark’s Structured streaming, and talk about new ideas yet to come. In the end, you can expect to have a much better understanding of the key concepts underpinning data processing, regardless of whether that data processing batch or streaming, SQL or programmatic, as well as a concrete notion of what robust stream processing in SQL looks like.