Tag: Statistics
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Enhancing Apache Spark and Parquet Efficiency: A Deep Dive into Column Indexes and Bloom Filters
Enhancing Apache Spark and Parquet Efficiency: A Deep Dive into Column Indexes and Bloom Filters In the ever-evolving landscape of big data, Apache Spark and Apache Parquet continue to introduce game-changing features. Their latest updates have brought forward significant enhancements, including column indexes, bloom filters. This blog post delves into these new features, exploring their
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Optimizer Statistics Gathering – pending and history
Optimizer Statistics Gathering – pending and history How do you manage when you need to gather statistics on some tables in a critical environment? Some queries are too long because of stale statistics. But other queries on the same tables are ok. You cannot leave the inital problem without fixing it. Adding hints or SQL
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Scaling up Cardinality Estimates in 12.1.0.2
Scaling up Cardinality Estimates in 12.1.0.2 Topic: Counting the number of distinct values (NDV) for a table column has important applications in the database domain, ranging from query optimization to optimizing reports for large data warehouses. However the legacy SQL method of using SELECT COUNT (DISTINCT <COL>) can be very slow. This is a well