Learning term
Database index — PostgreSQL
Database index accelerates matching search and sort operations at the cost of storage and writes. This card shows its role in “PostgreSQL” and a safe diagnostic path.
Orientation
Database index accelerates matching search and sort operations at the cost of storage and writes. At this level, separate purpose, input, and visible result. Place Database index within PostgreSQL before changing settings or files.
Practical use
Use EXPLAIN when a common query remains slow despite an index. Start in a sandbox with neutral examples. Record the expected state, make one controlled change, and compare status output, application behavior, and logs.
Technical understanding
Database index accelerates matching search and sort operations at the cost of storage and writes. Technically, Database index connects through interfaces, configuration, state, or dependencies. Trace data from input to output and check versions, permissions, networking, storage, and resources separately.
Operations and debugging
Use EXPLAIN when a common query remains slow despite an index. In production-like operations, use measurable signals, least privilege, reproducible configuration, and a documented rollback. Preserve evidence, isolate the cause, and verify the correction with the same test.
Exercise
Try it safely
Use EXPLAIN when a common query remains slow despite an index. Open an isolated test environment and run “psql --version && printf "%s\n" "SELECT 1;"”. Write down the expected output first, do not alter production data, and record one safe next diagnostic step.
psql --version && printf "%s\n" "SELECT 1;"Quick check
Can you explain the purpose, observable state, and most common failure source of Database index — PostgreSQL in one sentence each? Which evidence would you preserve before changing anything, and which repeated test would prove that the correction actually worked?