It's the last part of the series about the Adaptive Query Execution in Apache Spark SQL. So far you learned about the physical plan optimizations. But they're not alone and you will see that in this blog post.
So far you learned about skew optimization and coalesce shuffle partition optimizations made by the Adaptive Query Execution engine. But they're not the single ones and the next one you will discover is also related to the shuffle.
Apart from big and complex changes in the Adaptive Query Execution like skews or partitions coalescing, there are also some others, less complex. Although their smaller complexity, it doesn't mean they are not important. Especially when one of these changes offers a reuse of the subqueries.
Shuffle partitions coalesce is not the single optimization introduced with the Adaptive Query Execution. Another one, addressing maybe one of the most disliked issues in data processing, is joins skew optimization that you will discover in this blog post.
In my previous blog post you could learn about the Adaptive Query Execution improvement added to Apache Spark 3.0. At that moment, you learned only about the general execution flow for the adaptive queries. Today it's time to see one of possible optimizations that can happen at this moment, the shuffle partition coalesce.
A query adapting to the data characteristics discovered one-by-one at runtime? Yes, in Apache Spark 3.0 it's possible thanks to the Adaptive Query Execution!
