Autovacuum

autovacuum

• What it does: Controls whether the automatic vacuum and analyze daemon is enabled for the PostgreSQL instance.
• Why it matters: Autovacuum is essential for database maintenance as it automatically removes dead tuples (deleted or updated rows) and updates table statistics. Disabling it leads to table bloat, degraded query performance, and eventually risks transaction ID wraparound which can cause database downtime and data loss.
• Ideal value & Best Practice: on (enabled). This should never be disabled in production environments. For temporary maintenance operations, consider using transaction-specific settings rather than disabling globally.

autovacuum_analyze_scale_factor

• What it does: Determines the fraction of tuples (rows) that must be inserted, updated, or deleted before ANALYZE operations are triggered on a table.
• Why it matters: Controls how frequently table statistics are updated for the query planner. Outdated statistics can lead to poor query plans and degraded performance. This parameter works in conjunction with autovacuum_analyze_threshold.
• Ideal value & Best Practice: Default 0.1 (10%). For large tables (millions of rows), consider lowering this to 0.01-0.05% to ensure more frequent statistics updates. For small, frequently updated tables, you may need even lower values.

autovacuum_analyze_threshold

• What it does: Sets the minimum number of tuple changes (inserts, updates, deletes) required before triggering an ANALYZE operation, regardless of the scale factor.
• Why it matters: Ensures that small tables receive regular statistics updates even if they don't meet the percentage-based threshold. This prevents the query planner from using stale statistics for small but frequently modified tables.
• Ideal value & Best Practice: Default 50. For very large tables, increase this value to 100-500 to avoid excessive analyze operations. For critical small tables, you might lower it to ensure maximum plan accuracy.

autovacuum_freeze_max_age

• What it does: Specifies the maximum transaction age (in terms of transaction IDs) before autovacuum forces a vacuum operation to prevent transaction ID wraparound.
• Why it matters: This is a critical safety parameter that prevents catastrophic database failure. PostgreSQL uses a 32-bit transaction ID counter that can wrap around, potentially causing data loss if not managed properly. This parameter ensures vacuum occurs before wraparound becomes imminent.
• Ideal value & Best Practice: Default 200000000 (200 million). Do not increase this value beyond the default. Monitor wraparound warnings and ensure autovacuum can keep up with your workload to avoid emergency vacuums.

autovacuum_max_workers

• What it does: Controls the maximum number of autovacuum worker processes that can run simultaneously across the entire database cluster.
• Why it matters: Determines how many tables can be vacuumed or analyzed concurrently. Too few workers may cause vacuum to fall behind, while too many can consume excessive system resources and impact production workload performance.
• Ideal value & Best Practice: Default 3. For larger databases (100+ GB), increase to 5-8 workers. Monitor system resources and adjust accordingly. The optimal value depends on your CPU cores, I/O capacity, and workload characteristics.

autovacuum_multixact_freeze_max_age

• What it does: Sets the maximum multixact age before autovacuum forces a vacuum to prevent multixact ID wraparound.
• Why it matters: Prevents corruption of shared row locks that use multixact (multiple transaction) identifiers. Similar to transaction ID wraparound, multixact wraparound can cause database instability if not properly managed.
• Ideal value & Best Practice: Default 400000000 (400 million). Like autovacuum_freeze_max_age, this should not be increased. Ensure your autovacuum configuration can handle the workload to prevent emergency operations.

autovacuum_naptime

• What it does: Specifies the delay between autovacuum rounds, controlling how frequently the autovacuum launcher process checks for tables that need vacuuming.
• Why it matters: Affects how quickly autovacuum responds to table maintenance needs. Shorter naps make autovacuum more responsive but increase overhead, while longer naps reduce overhead but may allow bloat to accumulate longer.
• Ideal value & Best Practice: Default 1min. For busy databases with frequent updates, consider reducing to 30s. For quieter systems, increasing to 2-5min can reduce overhead. Monitor table bloat to find the right balance.

autovacuum_vacuum_cost_delay

• What it does: Introduces a delay in autovacuum operations when they reach the cost limit, helping to balance vacuum I/O with regular database workload.
• Why it matters: Prevents autovacuum from consuming excessive I/O resources and impacting production queries. This is part of PostgreSQL's cost-based vacuum delay feature that helps maintain system responsiveness during maintenance operations.
• Ideal value & Best Practice: Default 20ms. For systems with fast storage (SSD/NVMe), consider reducing to 10ms or even 5ms to allow more aggressive vacuuming. For slower systems or those with heavy read workloads, you might increase to 50ms.

autovacuum_vacuum_cost_limit

• What it does: Sets the maximum cost accumulated before an autovacuum worker sleeps for the duration specified by autovacuum_vacuum_cost_delay.
• Why it matters: Works with the cost delay to throttle autovacuum I/O impact. Higher values allow more work between delays, making vacuum faster but potentially impacting other operations.
• Ideal value & Best Practice: Default -1 (inherits from vacuum_cost_limit, which defaults to 200). For systems with dedicated maintenance windows, consider increasing to 1000-2000 for faster vacuum completion. For systems needing minimal impact, keep at default or lower.

autovacuum_vacuum_insert_scale_factor

• What it does: Specifies the fraction of tuples that must be inserted before triggering a vacuum operation, specifically for insert-only workloads.
• Why it matters: Helps manage table bloat in append-heavy tables (e.g., logging tables, time-series data) where traditional update/delete-based vacuum triggers may not activate frequently enough.
• Ideal value & Best Practice: Default 0.2 (20%). For heavily inserted tables, consider lowering to 0.05-0.1. For tables with mixed workloads, you might need to balance this with the standard scale factor settings.

autovacuum_vacuum_insert_threshold

• What it does: Sets the minimum number of inserts required to trigger a vacuum operation, regardless of the insert scale factor.
• Why it matters: Ensures that small insert-heavy tables receive regular vacuum attention even if they don't meet the percentage-based threshold. This helps prevent bloat in tables that are frequently written to but have relatively few rows.
• Ideal value & Best Practice: Default 1000. For very large tables, you might increase this to 5000-10000. For critical small tables with high insert rates, consider lowering to 500.

autovacuum_vacuum_scale_factor

• What it does: Determines the fraction of tuples that must be updated or deleted before triggering a vacuum operation.
• Why it matters: Controls how frequently vacuum operations occur for update/delete-heavy tables. Proper setting prevents excessive table bloat while avoiding unnecessary vacuum overhead.
• Ideal value & Best Practice: Default 0.2 (20%). For large tables, reduce to 0.05-0.1. For small tables, you might need even lower values. Consider table-specific settings for critical tables.

autovacuum_vacuum_threshold

• What it does: Sets the minimum number of updated or deleted tuples required to trigger a vacuum operation, regardless of the scale factor.
• Why it matters: Ensures that small tables with frequent update/delete activity receive regular vacuum attention. This prevents bloat in tables that may not meet the percentage threshold but still accumulate dead tuples rapidly.
• Ideal value & Best Practice: Default 50. For larger tables, increase to 100-500. For small but frequently updated tables, you might lower this to ensure timely vacuuming.

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