COURSE 19 OF 22
Distributed Processing with PySpark
Read execution plans, understand shuffles, and investigate skew before tuning.
Background reading
Introduction to Distributed Processing with PySpark
A delivery aggregation runs on a cluster, but one task takes much longer than the rest. Adding workers does not necessarily help: the slow task may still hold most of the data.
Spark divides work across partitions. A shuffle moves records between executors so matching keys can be processed together. Understanding where records move is the starting point for explaining cost.
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