{
  "schema": "pg36-ch28-maintenance-contract-v1",
  "hypothesis": "A snapshot older than the churn prevents ordinary VACUUM from removing every obsolete tuple; after the exact blocker is released, ordinary VACUUM can make that space reusable without requiring a heap rewrite.",
  "observation_order": [
    "baseline",
    "old-snapshot-acquired",
    "churn-complete",
    "vacuum-with-old-snapshot",
    "old-snapshot-released",
    "vacuum-freeze-complete",
    "amcheck-complete",
    "reindex-concurrently-complete",
    "partition-archive-round-trip-complete",
    "exact-cleanup-complete"
  ],
  "allowed_mutations": [
    "create marker-bound disposable login role",
    "create marker-bound disposable database",
    "install supplied extensions inside disposable database",
    "create and mutate chapter-owned fixture relations",
    "disable autovacuum only on the disposable churn table for determinism",
    "set vacuum cost controls only in the manual VACUUM session",
    "terminate exactly one marker-bound old-snapshot session",
    "run VACUUM, VACUUM FREEZE, amcheck, and REINDEX INDEX CONCURRENTLY on fixture objects",
    "detach, export, restore-check, and drop one fixture partition",
    "ordinary-drop the exact marker-bound database and role"
  ],
  "forbidden_mutations": [
    "ALTER SYSTEM",
    "edit Pigsty inventory",
    "edit Patroni dynamic configuration",
    "reload or restart PostgreSQL",
    "disable cluster-wide autovacuum",
    "VACUUM FULL",
    "DROP DATABASE FORCE",
    "terminate an unrelated session",
    "drop a partition before archive round-trip validation",
    "touch production data or traffic"
  ],
  "evidence": {
    "raw_private": true,
    "public_summary_allowlist": true,
    "source_hash_binding": true,
    "remote_temp_cleanup": true,
    "fixture_cleanup": true
  }
}