Skip to content

series

Reading Execution Plans

Three parts on turning a plan from a wall of text into a diagnosis — which EXPLAIN variant answers which question, the order to read a plan tree in, and the one comparison that localizes most problems.

1 part · 4 min total

PostgreSQL

The examples use PostgreSQL 18, but the reading order and the estimate-versus-actual comparison transfer to any cost-based optimizer. Read the parts in order: each one assumes the previous.

In this series

  1. Part 1: EXPLAIN, ANALYZE, BUFFERS: Three Different QuestionsWhich variant you ran decides whether the numbers in front of you are the planner's estimate or a measurement, and whether the pages came from cache. · 4 min

Start typing to search the archive.