Read the Execution Plan to See Which Access Path You Got, and Time It to See Which Step Cost You
This is the sub-domain's instrument, and it rests on the index and planner nodes because a plan is unreadable without knowing what a sorted structure and a row estimate are. Every diagnostic node after it — join method, the guilty statement, pagination cost — is an application of it, and it is what turns the curation's promise of explaining a slow request 'with numbers, not hope' into an actual procedure the learner performs.
Questions this Concept answers
What does running a statement with timings add that the plan alone cannot give you?
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jeremy
Video
Using EXPLAIN ANALYZE in PostgreSQL to See When an Index Replaces a Sequential Scan
`EXPLAIN` reports the execution plan a database's planner intends to use for a statement without running it, while `EXPLAIN ANALYZE` executes the statement and reports the plan actually taken togethe…