In any database environment, identifying and eliminating blocking queries is crucial for improving performance and ensuring smooth operations. The SQL Query Store, a feature introduced in SQL Server 2016, is a powerful tool that can help in this pursuit. It allows you to capture and analyze query performance metrics, including information about blocking queries. In this blog post, we will explore how to leverage the SQL Query Store to identify and eliminate blocking queries.

Table of Contents

1. Introduction to SQL Query Store
2. Enabling and Configuring SQL Query Store
3. Identifying Blocking Queries
4. Eliminating Blocking Queries
5. Conclusion

Introduction to SQL Query Store

The SQL Query Store is a built-in feature of SQL Server that collects and retains query performance data. It tracks different aspects of query execution, such as execution plans, runtime statistics, and query resource consumption. This makes it an invaluable tool for query performance tuning and troubleshooting.

Enabling and Configuring SQL Query Store

To enable and configure the SQL Query Store, you need to make sure it is enabled for your database. This can be done using the following T-SQL command:

ALTER DATABASE [DatabaseName] SET QUERY_STORE = ON;

Once enabled, you can configure various settings for the Query Store, such as data retention period, query capture mode, and statistics collection interval. These settings can be managed through the SQL Server Management Studio (SSMS) or programmatically using T-SQL commands.

Identifying Blocking Queries

One of the key benefits of the SQL Query Store is its ability to capture information about blocking queries. By querying the Query Store views, you can identify the queries that are causing blocking and gather insights into their execution patterns.

To identify blocking queries, you can use the following query against the Query Store views:

SELECT q.query_id, q.query_text, qs.execution_count, qs.avg_duration, qs.avg_logical_io_reads
FROM sys.query_store_query AS qs
JOIN sys.query_store_query_text AS qt ON qs.query_text_id = qt.query_text_id
JOIN sys.query_store_plan AS qp ON qs.plan_id = qp.plan_id
JOIN sys.query_store_runtime_stats AS rs ON qs.query_id = rs.query_id
WHERE rs.is_blocking = 1;

This query retrieves the query ID, query text, execution count, average duration, and average logical I/O reads for all queries that are identified as blocking. By analyzing this data, you can gain insights into the problematic queries that require optimization.

Eliminating Blocking Queries

Once you have identified the blocking queries, the next step is to eliminate them. There are several techniques you can employ to address blocking issues, such as optimizing query performance, restructuring your database schema, or modifying the query execution plan.

To optimize query performance, you can consider rewriting the query, creating appropriate indexes, or using query hints to guide the query optimizer. If the blocking is caused by locks, you can analyze the locking behavior and adjust isolation levels or lock timeout settings.

Additionally, you can leverage SQL Server tools like the Query Store Execution Plan Analysis and the Database Engine Tuning Advisor to get recommendations for query and index improvements.

Conclusion

The SQL Query Store is a valuable tool for identifying and eliminating blocking queries in a SQL Server environment. By leveraging the information captured in the Query Store views, you can gain insights into query performance and take necessary actions to improve overall database performance. Regularly monitoring and optimizing query performance can significantly enhance the efficiency and stability of your database system.

#hashtags: #SQLQueryStore #BlockingQueries