Statistics Archives - Page 2 Of 3 -

Improving Query Performance with Teradata Statistics Extrapolation and Object Use Counts (OUC)

04/11/202604/28/2023 by Roland Wenzlofsky

Teradata introduced several new features, including one that caught our attention: object use counts (OUC). This feature optimizes the calculation of extrapolated statistics, improving query performance significantly. Before version 13.10, changes made by DML statements were not logged, and the optimizer relied solely on dynamic amp sampling, leading to incorrect estimates for skewed tables. Additionally, …

Teradata Sample Statistics: When, How, and Why to Use Them

04/11/202604/28/2023 by Roland Wenzlofsky

Introduction to Teradata Sample Statistics Discover the optimal utilization of Teradata Sample Statistics, including when, how, and why to implement them. Sample statistics require columns with a high degree of diversity in values. A UPI satisfies this criterion, and only columns with numerous unique values should be considered for collecting sample statistics for the NUPI. …

How to Optimize Teradata Statistics and Avoid Heuristics: A Case Study

04/11/202604/28/2023 by Roland Wenzlofsky

The Optimizer typically excels in utilizing statistics, yet examining the execution plan and cardinality estimations can sometimes be beneficial. Since Teradata 14.10, I have habitually included the SHOW STATISTICS statement in my considerations. The resulting metrics can aid in identifying statistical issues. Teradata Statistics – Avoid the Heuristics This case study demonstrates how the Optimizer …

How to Improve Cardinality Estimations in Teradata: The Optimizer’s Toolkit

04/11/202604/28/2023 by Roland Wenzlofsky

Learn about Teradata Heuristics and Optimizer’s approach to estimating cardinality for non-indexed columns in this article. Discover how skew improves estimations and why heuristics should be avoided.

Teradata Statistics: Understanding and Using Collected Metrics for Optimal Query Performance

04/11/202604/28/2023 by Roland Wenzlofsky

Discover the importance of Teradata statistics in optimizing query execution plans. Learn how to collect statistics and when to use them for best results.

Teradata Statistics Extrapolation: What it is and How it Works

04/11/202604/27/2023 by Roland Wenzlofsky

Learn about Teradata Statistics Extrapolation, a technique that allows for reasonable estimations when querying historical data with stale statistics.

A Comprehensive Guide to Teradata Statistics: Common Misconceptions, Best Practices, and Real Reasons Behind Performance Degradation

04/11/202604/27/2023 by Roland Wenzlofsky

Learn the truth about Teradata statistics and their impact on system performance. Address common misconceptions, follow best practices, and optimize your system for peak performance.

Teradata Heuristics for Nonindexed Columns

04/11/202604/23/2023 by Roland Wenzlofsky

Learn about heuristics in Teradata optimizer and how they estimate the number of selected data rows for nonindexed columns in WHERE condition predicates. This post analyzes several queries and their estimates based on heuristics and provides insights on how to replace heuristic estimations with more accurate ones.

How to Use Biased Value Histograms for Accurate Statistics Estimation on Teradata SQL

04/11/202604/23/2023 by Roland Wenzlofsky

Learn how biased value histograms store exact cardinalities and provide up-to-date statistics for queries, and witness how the Optimizer estimates the number of rows for a given query.

Improvements in Tailoring Statistics Collection with Teradata 14.00: Using Sample, MaxValueLength, and MaxIntervals Options

04/11/202604/23/2023 by Roland Wenzlofsky

Learn about the latest improvements in Teradata 14.00 that allow you to customize the collection of statistics to better suit your needs. These improvements include the option to set different sample sizes, consider more bytes for histogram creation, and choose the number of intervals for building statistics histograms. Read on to discover how these changes can benefit your optimization efforts.