Trace performance issues in PostgreSQL using the pg_stat_statements

👉 The pg_stat_statements view is a PostgreSQL extension that provides information about the execution statistics of all SQL statements that have been executed by the PostgreSQL server. 

👉 You can use the pg_stat_statements view to trace performance issues by identifying the queries that are taking a long time to execute and then analyzing the execution plan for those queries. 

Here are some of the different ways to use the pg_stat_statements view to trace performance issues:

🔯 Identify the slow queries. You can use the total_time column to identify the queries that are taking a long time to execute. The queries with the highest total_time values are the ones that are most likely to be causing performance problems.

SELECT * FROM pg_stat_statements

ORDER BY total_time DESC

🔯 Identify the queries that are frequently executed. You can use the calls column to identify the queries that are frequently executed. The queries with the highest calls values are the ones that are most likely to be causing performance problems, even if they do not take a long time to execute individually.

SELECT * FROM pg_stat_statements

ORDER BY calls DESC;

🔯 Identify the queries that are using a lot of resources. You can use the rows and memory columns to identify the queries that are using a lot of resources. The queries with the highest rows values are the ones that are processing the most data. The queries with the highest memory values are the ones that are using the most memory.

SELECT * FROM pg_stat_statements

ORDER BY rows DESC;

🔯 Identify the queries that are changing their query plan frequently. You can use the plan_changes column to identify the queries that are changing their query plan frequently. The queries with the highest plan_changes values are the ones that are the most difficult for PostgreSQL to optimize.

SELECT * FROM pg_stat_statements

ORDER BY plan_changes DESC;

Once you have identified the queries that are causing performance problems, you can use the information in the pg_stat_statements view to analyze the execution plan for those queries. This can help you to understand why the queries are slow and how you can improve their performance.