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PostgreSQL Performance & Query Optimization · Lesson

Reading EXPLAIN and EXPLAIN ANALYZE Output

Decode PostgreSQL query plans with EXPLAIN to see how the planner executes a query and where the time really goes.

Why Read Query Plans

Before tuning a slow query, see what PostgreSQL actually does. EXPLAIN shows the planner's chosen execution plan as a tree of nodes.

EXPLAIN vs EXPLAIN ANALYZE

EXPLAIN shows estimates only; EXPLAIN ANALYZE actually runs the query and reports real timings and row counts — far more useful for diagnosis.

EXPLAIN ANALYZE
SELECT * FROM orders WHERE customer_id = 42;

All lessons in this course

  1. Understanding Database Performance Basics
  2. PostgreSQL Architecture Overview
  3. Basic Query Execution Workflow
  4. Reading EXPLAIN and EXPLAIN ANALYZE Output
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