Administración de PostgreSQL
EXPLAIN - tercer ejemplo

alvh=# EXPLAIN SELECT primario.primarioid FROM multi NATURAL JOIN primario ORDER BY primario.primarioid LIMIT 20;
NOTICE:  QUERY PLAN:

Limit  (cost=1301.45..1304.14 rows=20 width=8)
  ->  Merge Join  (cost=1301.45..3320.51 rows=15000
                   width=8)
        ->  Index Scan using primario_pkey on
            primario  (cost=0.00..1543.85 rows=100085
                       width=4)
        ->  Sort  (cost=1301.45..1301.45 rows=15000
                   width=4)
              ->  Seq Scan on multi
                  (cost=0.00..261.00 rows=15000
                   width=4)
EXPLAIN