seniorT-SQL

What is execution plan skew in parallel queries?

Updated May 17, 2026

Short answer

Plan skew occurs when work is unevenly distributed across parallel threads.

Deep explanation

In parallel execution, rows are distributed across worker threads. If distribution is uneven due to poor partitioning or skewed data, some threads finish early while others lag, causing CXPACKET or CXCONSUMER waits.

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