query store in sql server

DeWiadok Team

3 min read

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02-01-2025

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SQL Server Query Store is a powerful built-in performance monitoring and tuning tool introduced in SQL Server 2016. It provides a historical record of query execution statistics, enabling DBAs and developers to identify performance bottlenecks, understand query behavior over time, and optimize database performance. This detailed guide will walk you through the key aspects of Query Store, from its setup and configuration to its advanced features and best practices.

Understanding the Benefits of SQL Server Query Store

Before diving into the specifics, let's highlight the significant advantages Query Store offers:

• Proactive Performance Monitoring: Query Store automatically collects data on query execution plans, enabling proactive identification of performance regressions before they impact users.
• Historical Analysis: It maintains a historical record of query performance, allowing you to analyze trends and pinpoint the root causes of performance issues over time. This is invaluable for identifying performance changes related to schema changes, data growth, or application updates.
• Plan Comparison: Easily compare different execution plans for the same query, helping you identify less efficient plans and make informed decisions about query optimization.
• Reduced Performance Tuning Time: By providing comprehensive data on query behavior, Query Store dramatically reduces the time and effort required for performance tuning.
• Simplified Troubleshooting: Quickly pinpoint queries causing performance problems, saving valuable troubleshooting time.
• Regression Detection: Automatically identify queries exhibiting performance degradation, alerting you to potential issues before they impact production systems.

Setting Up and Configuring SQL Server Query Store

Enabling Query Store is a straightforward process:

1. Check for Compatibility: Verify your SQL Server version supports Query Store (SQL Server 2016 and later).
2. Enable Query Store: Use the following T-SQL command:

ALTER DATABASE [YourDatabaseName] SET QUERY_STORE = ON;

Replace [YourDatabaseName] with the name of your database.

3. Configure Query Store Options (Optional): You can further customize Query Store settings using the following options:

• MAX_STORAGE_SIZE_MB: Specifies the maximum storage size in MB. Default is 1024MB. Adjust this based on your needs and available disk space.
• DATA_FLUSH_INTERVAL_SECONDS: Determines how often data is flushed to disk. Default is 900 seconds (15 minutes).
• INTERVAL_LENGTH_MINUTES: Sets the time interval for collecting query statistics. Default is 60 minutes.
• FLUSH_INTERVAL_SECONDS: The interval at which data is flushed to disk. Default is 900 seconds.
• QUERY_CAPTURE_MODE: Defines which queries are captured. Options include ALL, AUTO, and NONE.

You can modify these options using the following T-SQL command:

ALTER DATABASE [YourDatabaseName] SET QUERY_STORE (
    MAX_STORAGE_SIZE_MB = 2048,  -- Example value
    DATA_FLUSH_INTERVAL_SECONDS = 600,  -- Example value
    INTERVAL_LENGTH_MINUTES = 30 -- Example Value
);

Analyzing Query Store Data

Once Query Store is enabled and data has been collected, you can analyze the collected information using SQL Server Management Studio (SSMS) or other tools. The key areas of focus include:

• Top Resource Consuming Queries: Identify the queries consuming the most resources (CPU, I/O, duration).
• Wait Statistics: Understand the types of waits experienced by queries. This is crucial for identifying bottlenecks like I/O waits or lock contention.
• Execution Plans: Analyze different execution plans for the same query to identify inefficiencies. This often involves comparing the estimated and actual execution times.
• Query Performance Trends: Track query performance over time to detect regressions and performance degradation.

Advanced Features and Best Practices

• Automatic Tuning: SQL Server can automatically tune queries based on Query Store data. This involves automatically applying the best execution plan.
• Forced Plans: You can force a specific execution plan for a given query to address performance issues. However, this should be used cautiously.
• Cleaning Up Query Store: Regularly clean up old data to manage disk space usage. Use the ALTER DATABASE ... SET QUERY_STORE ... CLEANUP_POLICY option.

Conclusion

SQL Server Query Store is an indispensable tool for performance tuning and monitoring in modern SQL Server environments. Its ability to automatically collect, store, and analyze query execution statistics empowers DBAs and developers to proactively identify and address performance bottlenecks, significantly improving database performance and overall system reliability. By understanding its features, configuration options, and best practices, you can leverage Query Store to its fullest potential. Remember to regularly monitor your Query Store data and adjust configurations as needed to ensure optimal performance for your specific workload.