Using pg_stat_statements in PostgreSQL

1. Introduction

The pg_stat_statements extension is a crucial tool for PostgreSQL performance optimization. It allows you to track execution statistics of all SQL statements executed by your database.

2. Installation

To use pg_stat_statements, you need to install it and enable it in your PostgreSQL configuration.

Step-by-Step Installation

Connect to your PostgreSQL database.
Run the following command to create the extension:

CREATE EXTENSION pg_stat_statements;

Modify the postgresql.conf file to include pg_stat_statements in the shared_preload_libraries setting:

shared_preload_libraries = 'pg_stat_statements'

Restart your PostgreSQL server.

3. Configuration

After installation, configure the extension to suit your needs:

Configuration Parameters

pg_stat_statements.max: The maximum number of statements tracked (default is 5000).
pg_stat_statements.track: Controls what statements are tracked (options: none, top, all). Default is all.
pg_stat_statements.track_utility: If set to on, it tracks utility commands like CREATE, ALTER, etc.

4. Usage

Once configured, you can query the statistics from the pg_stat_statements view.

SELECT * FROM pg_stat_statements ORDER BY total_time DESC;

This query retrieves all recorded statements sorted by total execution time.

5. Best Practices

To maximize the benefits of pg_stat_statements, consider the following best practices:

Regularly monitor and analyze the statistics to identify slow queries.
Adjust the pg_stat_statements.max setting based on your workload.
Use the statistics to inform indexing and query optimization strategies.

6. FAQ

What types of statements does pg_stat_statements track?

It tracks all types of SQL statements executed by the database, including SELECT, INSERT, UPDATE, DELETE, and utility commands (if configured).

Can I reset the statistics?

Yes, you can reset the statistics by executing SELECT pg_stat_statements_reset();.

Does pg_stat_statements impact performance?

While there is some overhead associated with tracking statistics, the benefits of optimizing queries often outweigh this cost.