Скачать или смотреть A Little About: Old vs New Cardinality Estimators In SQL Server

In this video, I delve into a specific example to explain why I generally prefer the legacy cardinality estimator over the new one in SQL Server. Using a query that involves finding missing IDs in an identity column, I demonstrate how the execution plans and performance can differ significantly between the two estimators. By comparing the results of running the same query with both the default and legacy cardinality estimators, I highlight why tuning queries using the legacy estimator can sometimes yield more efficient plans, even if there isn't a drastic difference in performance. This example serves as a practical guide for when to test out the legacy cardinality estimator during your query optimization process.

CHAPTERS

00:00:00 - Introduction
00:00:29 - Office Hours Question
00:01:29 - Channel Membership and Support
00:03:55 - Query Example Setup
00:04:10 - Table and Database Details
00:04:43 - Missing ID Explanation
00:07:31 - Execution Plans Comparison
00:08:41 - Single Threaded Plan

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