Mastering Apache Pulsar

Chapter 10. Pulsar SQL

At this point, we know we can interact with Pulsar in the following ways:

• Pulsar CLI

• Pulsar Admin API

• Pulsar clients

• Pulsar Functions

• Pulsar IO

Another way we can interact with Pulsar topics is through Structured Query Language (SQL). With Pulsar SQL, we can treat topics as tables and query them with SQL. However, before diving into how querying topics with SQL is possible, we should ask why do this at all? After all, using another tool or another language has some disadvantages that we should consider as well. Among these disadvantages are:

• Increased complexity from managing more semantics

• Cost considerations

• Cognitive overhead from managing new tools

We know Apache Pulsar is a storage system for event streams. With that lens, we can see the necessity and utility of alternative data interaction mechanisms. For example, with Pulsar Functions, we get a simple API that allows us to manipulate messages one at a time. With Pulsar IO, we get a repeatable mechanism for moving data to and from Pulsar topics. What advantage does querying a topic with SQL bring to the table?

SQL is the most ubiquitous programming language. Analytics engineers, designers, programmers, data scientists, and executives can all utilize it. In addition, popular databases like PostgreSQL, MySQL, Oracle, and Redshift all use a dialect of SQL to query data. Pulsar topics contain event data and are often the ingress point for an application. Enabling more people to access ...