In SQL Server, the Query Store is a powerful feature that helps database administrators and developers analyze the performance of queries and track query execution statistics over time. It provides valuable insights into query plans, resource consumption, and troubleshooting query performance issues.
What is the Query Store?
The Query Store is a performance monitoring and troubleshooting tool available in SQL Server 2016 and later versions. It collects and stores execution plans, runtime statistics, and other relevant information for each query executed on a database.
By capturing this information, the Query Store enables you to compare query performance metrics over different time intervals, identify query plan regressions, and make informed decisions to improve query performance.
Enabling and Configuring the Query Store
To enable the Query Store on a database, you can execute the following T-SQL statement:
ALTER DATABASE YourDatabase SET QUERY_STORE = ON;
By default, the Query Store captures query execution statistics and query plans for a retention period of 30 days. You can modify these settings to suit your specific requirements.
For example, to change the retention period to 7 days, you can execute the following statement:
ALTER DATABASE YourDatabase SET QUERY_STORE (OPERATION_MODE = READ_WRITE, CLEANUP_POLICY = (STALE_QUERY_THRESHOLD_DAYS = 7));
Analyzing Query Performance
Once the Query Store is enabled and configured, you can start utilizing its features to analyze query performance. Here are some common scenarios where the Query Store can be beneficial:
1. Identifying Query Plan Changes
The Query Store tracks changes in query plans over time. By comparing different versions of a query plan, you can easily identify plan changes that might have impacted performance. This helps in identifying plan regressions and taking corrective actions.
2. Troubleshooting Query Performance Problems
When facing performance issues with specific queries, the Query Store allows you to compare the execution plans, query statistics, and resource usage across different time intervals. This enables you to identify patterns, bottlenecks, and potential root causes of performance problems.
3. Assessing Query Performance Impact
The Query Store provides statistics on query duration, CPU usage, I/O consumption, and more. By analyzing this data, you can determine the performance impact of individual queries, identify resource-intensive queries, and optimize them for better performance.
Query Store Views and Functions
The Query Store provides a set of system views and functions that allow you to access the captured query data. Some important views and functions include:
- sys.query_store_query: Contains information about executed queries and their properties.
- sys.query_store_query_text: Stores the SQL text of executed queries.
- sys.query_store_plan: Stores the query plans associated with executed queries.
- sys.query_store_runtime_stats: Provides runtime statistics of executed queries.
These views can be queried to retrieve information about query performance, plan evolution, and execution statistics. By utilizing these views and functions effectively, you can unlock the full potential of the Query Store for query optimization and performance tuning.
Conclusion
The Query Store is a valuable tool for analyzing execution plans and query statistics in SQL Server. By enabling and configuring the Query Store and leveraging its features, database administrators and developers can gain detailed insights into query performance and make informed decisions to optimize and troubleshoot their databases.
With its ability to track query plan changes, troubleshoot performance problems, and assess the impact of queries, the Query Store is an essential tool in the SQL Server toolbox. Start utilizing the Query Store today and take your query performance analysis to the next level.