Read the basic signals in an EXPLAIN plan so you can choose the right next optimization move.
An EXPLAIN plan is a workload map. Read the work first. Start with node types, not folklore Sequential scans, index scans, joins, sorts, and aggregates each tell you what kind of effort the engine is about to spend. That is more actionable than vague rules like “seq scan bad” or “index scan good.” Then read the estimates Start-up cost, total cost, rows, and width describe what the planner believes. Wrong row beliefs are especially dangerous because they influence everything above them in the tree. Finally ask what optimization lever matches the evidence A giant sort may call for a better…
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