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Data & Analytics · Advanced

Data Skew

An uneven distribution of data across partitions, so a few tasks process far more data and slow the whole job.

Definition

Skew shows up as a few long-running tasks in a stage. Remedies include AQE skew-join handling, salting hot keys, broadcast joins and better partition keys.

Exam tip

One task running far longer than the others in a stage = skew.

Related terms