migrations: durable aggressive autovacuum for telemetry tables

server/migrations/0013_telemetry_autovacuum.sql

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+-- Aggressive per-table autovacuum for the high-churn telemetry tables. The 7-day
+-- retention prune deletes rows fine, but at Postgres' default 20% vacuum scale
+-- factor autovacuum effectively never fired on logs, metric_series_rollups, and
+-- spans — their steady insert+delete churn never crossed the 20%-of-table
+-- threshold before the table itself had grown, so dead tuples were never
+-- reclaimed and the DB ballooned to 77 GB of bloat. Lowering the scale factor to
+-- 2% (and matching the insert-triggered vacuum) makes autovacuum run often enough
+-- to keep up with the prune's delete churn, and the raised cost limit lets each
+-- run actually make progress instead of throttling to a crawl. These were applied
+-- live via ALTER TABLE; this migration makes that tuning durable across a DB
+-- recreate.
+ALTER TABLE logs SET (
+    autovacuum_vacuum_scale_factor = 0.02,
+    autovacuum_vacuum_cost_limit = 2000,
+    autovacuum_vacuum_insert_scale_factor = 0.02
+);
+
+ALTER TABLE metric_series_rollups SET (
+    autovacuum_vacuum_scale_factor = 0.02,
+    autovacuum_vacuum_cost_limit = 2000,
+    autovacuum_vacuum_insert_scale_factor = 0.02
+);
+
+ALTER TABLE spans SET (
+    autovacuum_vacuum_scale_factor = 0.02,
+    autovacuum_vacuum_cost_limit = 2000,
+    autovacuum_vacuum_insert_scale_factor = 0.02
+);