Interview Q&A / PostgreSQL
PostgreSQL interview questions
Indexes, EXPLAIN, transactions and isolation, JSONB and the Postgres specifics backend interviews probe.
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- What do the cost numbers in an EXPLAIN plan actually mean?
cost=A..B gives the estimated startup cost (before the first row) and total cost, in arbitrary planner units based on page fetches and CPU work. They are for comparing plans, not seconds or milliseconds.
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