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…le queries These queries used CROSS JOIN with pg_database or UNNEST to produce zero-filled result sets, causing memory pressure proportional to (lock_modes × databases) or (idle_connections × bucket_count). - pg_locks: replace VALUES CROSS JOIN pg_database with direct JOIN, only returning lock modes actually held - pg_stat_activity: remove VALUES CROSS JOIN pg_database, query pg_stat_activity directly with GROUP BY - pg_process_idle: replace UNNEST implicit cross-join with raw query and Go-side histogram bucketing; also fixes existing bug where QueryRowContext only processed a single (state, application_name) group
Replace per-database metrics (19 metrics × N databases) with a single aggregated row containing only metrics not available from other collectors: xact_commit, xact_rollback, temp_files, temp_bytes, deadlocks, blk_read_time, blk_write_time, active_time. Metrics that duplicate pg_stat_activity, pg_stat_user_tables, or pg_statio_user_tables (numbackends, blks_read, blks_hit, tup_*) are removed. The datid/datname labels are dropped. This is a breaking change for anyone querying these metrics by database name.
Benchmarks pg_locks, pg_stat_database, pg_stat_user_tables, pg_statio_user_tables, and pg_database at various scale points (100/500/1000/5000) to measure allocation growth as catalog objects increase.
Before running expensive queries, collectors now check the row count against a configurable limit. When exceeded, the collector skips metric emission and instead emits a pg_exporter_collector_rows_exceeded gauge with the actual count. Flags added: --collector.stat_user_tables.max_rows (default: 375) --collector.statio_user_tables.max_rows (default: 750) --collector.database.max_rows (default: 750) Set to 0 to disable the limit. Defaults derived from benchmark data targeting ~4MB per collector within a 32MiB memory budget.
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