In SQL Server, the Query Store feature is a powerful tool that allows you to capture and analyze query performance information. It records query execution plans, runtime statistics, and other query-related information, giving you insights into query performance over time. However, effectively interpreting and analyzing the data in the Query Store can be a daunting task. In this blog post, we will explore some tips and techniques to help you make the most out of the SQL Query Store.
Table of Contents
- Enabling Query Store
- Understanding Query Store data
- Analyzing Query Store data
- Identifying performance bottlenecks
- Query tuning with Query Store
- Conclusion
Enabling Query Store
Before diving into data analysis, it’s important to enable the Query Store feature on your SQL Server database. To enable Query Store, you can use the following T-SQL command:
ALTER DATABASE YourDatabase SET QUERY_STORE = ON;
Once enabled, Query Store starts capturing query performance information and storing it in the database.
Understanding Query Store data
Query Store stores information in various tables that you can query and analyze. The main tables include sys.query_store_query, sys.query_store_query_text, and sys.query_store_plan, among others. These tables provide valuable information such as query text, execution plans, runtime statistics, and average resource consumption.
To effectively interpret the data, you need to be familiar with the schema of these tables and understand the relationship between them. Microsoft provides detailed documentation on the structure of Query Store tables, which can help you navigate and analyze the data effectively.
Analyzing Query Store data
To analyze Query Store data, you can use T-SQL queries to extract the relevant information from the Query Store tables. For example, you can retrieve the top 10 most expensive queries based on average CPU time using the following query:
SELECT TOP 10 *
FROM sys.query_store_query
ORDER BY average_cpu_time DESC;
You can also compare query performance metrics over time by querying the runtime statistics tables, such as sys.query_store_runtime_stats_interval or sys.query_store_runtime_stats_interval_internal. These tables provide detailed information on query execution duration, CPU usage, and IO usage.
Another useful analysis technique is to compare execution plans of a specific query between different time intervals. By querying the sys.query_store_plan table and examining the plan XML, you can identify any changes in the execution plan that may be impacting query performance.
Identifying performance bottlenecks
When analyzing Query Store data, it’s essential to identify performance bottlenecks. Look for queries with high average duration, CPU time, or IO usage. These queries may indicate potential performance issues that need to be addressed.
Additionally, pay attention to queries with frequently changing execution plans. Query Store can capture plan regressions, which occur when the execution plan for a query suddenly becomes less optimal. Identifying and addressing plan regressions can significantly improve query performance.
Query tuning with Query Store
One of the major benefits of Query Store is its ability to facilitate query tuning. By leveraging the historical query performance data captured in the Query Store, you can identify poorly performing queries and explore different execution plans.
Using tools like SQL Server Management Studio (SSMS) or third-party query tuning tools, you can force a specific execution plan for a query, monitor its performance, and compare it with the previous plan. This iterative process of identifying, tuning, and comparing different execution plans can help optimize query performance.
Conclusion
The SQL Query Store is a valuable feature for capturing and analyzing query performance information in SQL Server. By enabling Query Store, understanding the schema of the Query Store tables, and analyzing the captured data, you can effectively identify performance bottlenecks and optimize query execution. With its query tuning capabilities, Query Store enables you to fine-tune query performance by exploring different execution plans. Utilizing these techniques will help you make well-informed decisions to improve the overall performance of your SQL Server database.
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