Welcome to this deep dive into the architecture and internals of the SQL Query Store. In this blog post, we will uncover how the SQL Query Store works under the hood and explore its key components and features.

Table of Contents

1. Introduction
2. Architecture
3. Key Components
4. Working Mechanism
5. Features
6. Conclusion

Introduction

The SQL Query Store is a powerful feature introduced in SQL Server 2016 and later versions. It is designed to capture a history of executed queries along with their corresponding execution plans and performance metrics. This allows database administrators and developers to closely monitor and analyze the performance of queries over time.

Architecture

The architecture of the SQL Query Store consists of two main components: the Query Store repository and the Query Store views.

Query Store Repository

The Query Store repository is a system database known as query_store. It stores the captured query information in a structured manner, including query text, execution plans, runtime statistics, and other related metadata. The data is organized into time-based partitions, allowing for efficient querying and analysis.

Query Store Views

SQL Server provides a set of system views, such as sys.query_store_query_text, sys.query_store_plan, and sys.query_store_runtime_stats, which allow users to access and retrieve the captured query data from the Query Store repository. These views provide a simplified interface to perform detailed analysis on query performance.

Key Components

The SQL Query Store consists of several key components:

1. Query Text: The actual text of the executed query.
2. Execution Plans: The generated execution plans for each query.
3. Runtime Statistics: The performance metrics associated with query execution, including CPU time, logical reads, and duration.
4. Query Parameters: The parameter values used in query execution.
5. Plan Forcing: The ability to force a specific execution plan for a given query.
6. Historical Data: A history of executed queries and their associated statistics.

Working Mechanism

The SQL Query Store captures query information using an automated data collection process. Whenever a query is executed, the relevant data is collected and stored in the Query Store repository. This process is transparent and does not require any manual intervention.

Once the data is stored, it can be accessed using the Query Store views, allowing users to analyze query performance, identify performance regressions, and troubleshoot query-related issues.

Features

The SQL Query Store comes with a range of powerful features:

1. Query Performance Analysis: Users can analyze query performance over time, identify top resource-consuming queries, and track performance trends.
2. Plan Comparison: The Query Store allows for easy comparison of different execution plans for the same query, enabling users to identify plan changes and their impact on performance.
3. Plan Forcing: Users can force a specific execution plan for a query, helping to stabilize query performance in case of plan regressions.
4. Automatic Tuning: The Query Store can provide recommendations for plan forcing or plan regression fixes based on historical query performance data.

Conclusion

In this deep dive, we explored the architecture and internals of the SQL Query Store. We learned about its key components, working mechanism, and powerful features that enable detailed analysis and monitoring of query performance.

The SQL Query Store is a valuable tool for database administrators and developers to gain insights into query execution and optimize application performance. Whether you are troubleshooting performance issues or proactively monitoring query performance, the SQL Query Store can be a great asset in your SQL Server environment.

Try leveraging the SQL Query Store in your next project and unlock its potential to improve query performance and optimize resource utilization.

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