Statistics Archives - Page 5 Of 7 -

Understanding Teradata Load Isolation

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

Isolation Levels and their Impact on Performance & Concurrency Isolation is a crucial factor in determining the visibility of transaction integrity to database users. This property guarantees that concurrently executed transactions produce identical results to those executed sequentially. Nonetheless, relinquishing this requirement can enhance transaction concurrency, improving performance. However, this also implies accepting inconsistent outcomes. …

Building a Teradata Data Warehouse: Considerations for ETL Process, SQL Queries, and Physical Data Model

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

This post aims to compile all crucial aspects to be considered while constructing a Teradata Data Warehouse, including the ETL process and SQL queries. This list is just the beginning, and I anticipate receiving valuable feedback from my readers to expand it in the future. Initially, I have provided a few concepts, but I intend …

Optimizing Teradata Joins: Handling Skewed Workloads with Partial Redistribution and Partial Duplication

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

How does Teradata handle Skew in Joins? The imbalanced workload is a primary issue that must be addressed in performance optimization. Efficient optimization is crucial for join steps due to the possibility of Teradata transferring significant data volumes between AMPs. The optimizer can perform joins separately for primary index values that are skewed and those …

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. …

Teradata Table Design Checklist: Primary Index, Character Set, and Data Type Considerations

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

Teradata Table Design Checklist As creating tables is a frequent task, I deemed it necessary to provide a checklist. 1. Primary Index Or NOPI Table? The Primary Index serves multiple purposes, primarily functioning as the primary access path to the data and being optimized for an even distribution of rows. However, designing a table without …

Achieve Incredible Teradata Join Performance

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

Executive summaryGUEST POST BY ARTEMIY KOZYR Today I shed some light on how Data Warehousing lies at the core of Retail Banking operations. We will see the actual case of vital marketing process malfunction and dive deep under the surface level to comprehend data alchemy technical issues. You will learn how to approach such issues, …

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 …

Optimizing Teradata Requests with Group-AMP Operations for Improved Performance

03/08/202604/28/2023 by Roland Wenzlofsky

All-AMP and single-AMP operations are well-understood. All-AMP retrieval typically involves full table scans, including NUSI sub-table scans. On the other hand, single-AMP retrieval typically involves indexed access, such as UPI and NUPI. Group-AMP operations optimize requests by minimizing the number of active AMPs. These operations fall between single-AMP and all-AMP operations. The Optimizer employs group-AMP …

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 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.