What is EXPLAIN ANALYZE, what is it used for, and how does it work?

EXPLAIN ANALYZE is a command in SQL (for example, in PostgreSQL) used to analyze the execution of a query. It shows how the DBMS plans and executes the query, as well as how long each operation takes.

When you run EXPLAIN ANALYZE before an SQL query, the database first executes the query and then outputs a detailed execution plan with actual time costs and the number of rows processed.

This helps to:

• Understand which indexes are used or not used.
• Identify bottlenecks in the query.
• Optimize queries to improve performance.

Example of usage:

EXPLAIN ANALYZE SELECT * FROM users WHERE age > 30;

The result will show a sequence of operations (table scan, filtering, sorting, etc.) with the time and number of rows at each step.

Thus, EXPLAIN ANALYZE is a powerful tool for diagnosing and optimizing SQL queries.