Cardinality Estimation in Apache Spark 2.3 (Ron Hu & Zhenhua Wang)

431 views · Published 27 September 2018 · 30:15 · Indexed 21 September 2026

Channel: Databricks · 2018 · Science & Technology

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Ron Hu, a Principal Big Data Architect at Huawei Technologies, and Zhenhua Wang, a Research Engineer at Huawei Technologies, explain how Apache Spark 2.2 shipped with a state-of-art cost-based optimization framework that collects and leverages a variety of per-column data statistics (e.g., cardinality, number of distinct values, NULL values, max/min, avg/max length, etc.) to improve the quality of query execution plans. Skewed data distributions are often inherent in many real world applications. In order to deal with skewed distributions effectively, we added equal-height histograms to Apache Spark 2.3. Leveraging reliable statistics and histogram helps Spark make better decisions in picking the most optimal query plan for real world scenarios.


Learn more here: https://databricks.com/session/cardinality-estimation-through-histogram-in-apache-spark-2-3

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