EXPLAIN ANALYZE Cost Optimizer Lab

Interactive evaluation of Seq Scan, Index Scan, Index-Only Scan, and Bitmap Index Scan execution plans.

PostgreSQL Cost-Based Optimizer (CBO)

EXPLAIN (ANALYZE, BUFFERS) Plan Inspector

Cost Estimation & Execution Latency

psql explain output100,000 Rows Table

Index Scan using idx_orders_user_id on orders (cost=0.42..8.45 rows=2 width=32)
  Index Cond: (user_id = 942)
  Buffers: shared hit=3 (B-Tree) read=1 (Heap)
Planning Time: 0.110 ms
Execution Time: 0.082 ms

Optimizer Decision Analysis:

B-Tree Index Scan + Table Heap Fetch

Traverses the 3-level B-Tree index in 0.05ms, then fetches the exact 2 matching rows from the heap data page.

CBO Cost Formula:

Cost = (pages * seq_page_cost) + (tuples * cpu_tuple_cost)