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Coordinator DB
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Inspect query measurements ​

Measurements describe a concrete execution, not an abstract SQL spelling. Keep its SQL, parameters, data and query ID together when investigating a request.

Find the execution ​

Read the query ID from an HTTP response header or query history. Use system.query_log for finished requests and system.processes for active requests.

Compare elapsed time with read_rows, read_bytes, written_rows and written_bytes. Terminal memory_usage and peak_memory_usage both report the query's peak accounted memory, rather than a post-completion live allocation.

Inspect the plan ​

EXPLAIN QUERY PLAN shows access choices without executing the statement. EXPLAIN ANALYZE executes once and includes runtime measurements:

text
EXPLAIN ANALYZE
SELECT generate_series
FROM generate_series(1, 3);

Analyzed output replaces the underlying result rows. EXPLAIN ANALYZE also applies DML changes once; use a transaction and rollback when those changes should not remain.

Compare runs ​

Durations vary between executions. Keep result limits and data fixed, verify that both queries perform the intended work, and inspect the plan alongside timings.

See EXPLAIN and query history.