How to Improve SQL Server Performance with Query Store and Plan Forcing
Welcome to this in-depth exploration of the powerful tools designed for SQL Server optimization: Query Store and Plan Forcing. SQL Server professionals constantly look for strategies to boost the performance of their databases, especially as system complexity and data volume continue to grow. With these tools, database administrators and developers are better equipped to handle performance tuning, identify problematic queries, and stabilize plan choices. This article aims to present a comprehensive analysis of how you can use Query Store and Plan Forcing to refine SQL Server performance.
Understanding Query Store
Before delving into the specifics of performance improvement, it’s important to clarify what Query Store is. Introduced in SQL Server 2016, Query Store operates as a type of ‘flight recorder’ for SQL Server, tracking query execution statistics and query plan history. It remains a pivotal component of performance tuning capabilities, allowing the retention of vital information about query execution and effectiveness over time. By using Query Store, database administrators can converse with historical data to understand the query performance patterns, isolate performance degradation, and address it with confidence.
Enabling and Configuring Query Store
By default, the Query Store feature is disabled, and it must be enabled per database. Turning on Query Store involves configuring several options like data flush interval, statistics collection interval, maximum storage size, and data retention policy. These settings help in fitting the Query Store behavior in line with your particular maintenance preferences and performance needs.
Here’s how to enable Query Store:
USE [YourDatabaseName];
GO
ALTER DATABASE [YourDatabaseName] SET QUERY_STORE = ON;
GO
Once enabled, the Query Store begins collecting data, which can later be queried and reported.
Utilizing Query Store for Performance Analysis
Query Store allows for the analysis of query performance across different dimensions such as execution time, memory consumption, and I/O reads/writes. It presents visual tools for a quicker identification of regressed queries, enabling database professionals to pin the problematic and expensive queries effectively. Query Store also supports drill-downs into detailed query execution plans and runtime stats, providing a clearer picture of the optimization opportunities at hand.
For analyzing and improving performance, SQL users can follow these steps:
- Identify high-impact queries using Query Store reports.
- Analyze query execution plans and performance metrics.
- Compare plan performance from different time periods.
- Use the insights gathered to adjust indexing, rewrite problematic queries, or manage plan choice.
Introduction to Plan Forcing with Query Store
One of the vital features of Query Store is plan forcing. It addresses the common problem of query plan regression, where the SQL Server execution engine might choose a less optimal plan under certain conditions, such as parameter sniffing or statistical variations. This can cause a once-fast query to run slower due to change in the execution plan. Plan forcing enables administrators to ‘lock in’ a particular plan for a query. When enabled, SQL Server makes sure that, for a problem query, the identified optimal plan is used consistently, preventing unexpected regressions.
How to Use Plan Forcing with Query Store
Engaging Plan Forcing through Query Store follows a precise sequence:
- First, find the plan that performs best for your query within the Query Store UI.
- Select that plan, and you will be given the option to force it.
- Once forced, the SQL Server will use that plan each time the query is executed.
You can apply Plan Forcing manually or leverage automatic plan correction if you’re running SQL Server 2017 or later. Automatic plan correction monitors and automatically applies plan forcing if it detects a regression in query performance.
Monitoring Performance After Applying Plan Forcing
After forcing a plan, it’s necessary to monitor its impact. This involves using Query Store to track the performance of the forced query over time. Look out for metrics indicating an improvement but also remain vigilant about any unforeseen negative side effects that may require plan unforcing or a different optimization tactic.
Best Practices for Using Query Store and Plan Forcing
There are several best practices when using Query Store and Plan Forcing effectively:
- Start by solving high-impact performance issues. Focus on critical systems and foreground queries with the most noticeable impact on performance.
- Identify the root cause of performance issues—it could be indexing, statistics, or the plan itself. Avoid enforcing plans without a thorough analysis.
- Maintain a proactive monitoring approach, reviewing Query Store data regularly to identify potential performance degradation in advance.
- Balance between Query Store size/data retention and server performance. Too much data may affect performance, while too little data might render Query Store ineffective for analysis.
- Use Plan Forcing with caution. Always test the effects of plan forcing in a non-production environment first, and monitor after applying in production.
- Understand that Plan Forcing is not a silver bullet. While it can stabilize performance, it might not be the best long-term solution for all cases.
Advanced Features: Extended Events and Monitoring Tools
For a more detailed analysis, SQL Server’s Extended Events can be combined with Query Store for a granular look into server behavior. Custom events and sessions can be configured to augment the data collected through Query Store, aiding in an even deeper diagnosing of performance issues.
In addition to Query Store and native tools, third-party monitoring solutions may offer an expanded set of features and analytics to manage database performance, integrating transparently with Query Store data and Plan Forcing operations.
Conclusion
Query Store and Plan Forcing represent a paradigm shift in database performance optimization. They provide SQL Server professionals with tangible and reliable methods to boost efficiency and stability in their database systems. Careful application of the strategies discussed—by assessing, enforcing, monitoring, and potentially revising forced plans—can significantly improve your SQL Server environment’s performance. Embrace these tools, but remember: a thoughtful and informed approach is the key to achieving optimized database performance.
