Lesson 3 of 11 · 22 min
EXPLAIN ANALYZE: what really happened
By the end of this lesson you can run EXPLAIN ANALYZE safely, read actual time, actual rows, loops and Rows Removed by Filter, and spot an estimate that is far from reality.
EXPLAIN ANALYZE plans the query, runs it, throws the result rows away and prints the plan with measurements added to every node. In PostgreSQL 18 it also reports buffers (8 kB pages found in memory, hit, or read from storage, read) by default.
This lesson, its 3 graded exercises and every other Members lesson in SQL Quest come with a Formula Quest membership that includes SQL (Single Quest with SQL selected, Quest Trio including SQL, or Quest Unlimited), or with SQL access from your organization.
Free to everyone: all of SQL Foundations and Retrieving and Filtering Data, the first lesson of every track, the playground, the dataset library and the SQL reference. See free lessons