Reading query plans

Run it correctly

EXPLAIN (ANALYZE, BUFFERS, SETTINGS, FORMAT TEXT) SELECT ...;

• ANALYZE executes the query. For UPDATE or DELETE, wrap it in a transaction and roll back.
• BUFFERS is the commonly omitted flag that matters most: it shows how much data was actually touched.
• SETTINGS shows non-default planner parameters, which explains environment differences.

BEGIN;
EXPLAIN (ANALYZE, BUFFERS) UPDATE ...;
ROLLBACK;

Start with estimate versus actual