{"id":"btree-durability-protects-data-not-structure","text":"The B-tree's durability model protects user data but not structural integrity: mutations pay double fsync for data pages (WAL entry + data write) while structural metadata is never fsynced, AND structural integrity silently erodes during normal operation (leaked pages, ever-growing height, dangling parent pointers after free_page) with no defensive checks in the I/O layer to detect or prevent degradation.","truth_value":"OUT","source":"","source_url":"","source_hash":"","justifications":[{"type":"SL","antecedents":["btree-structural-integrity-silently-erodes","btree-mutation-fsync-is-asymmetric"],"outlist":[],"label":"Fsync asymmetry protects the values but not the tree shape, while the tree shape degrades monotonically — durability effort is precisely misallocated"}],"dependents":["full-stack-restart-fragility"],"metadata":{"last_reviewed":"2026-05-30T09:01:17","review_result":"pass"},"created_at":"","updated_at":"","reviewed_at":"","verified_at":"","retracted_at":"","explanation":{"steps":[{"node":"btree-durability-protects-data-not-structure","truth_value":"OUT","reason":"SL justification invalid","failed_antecedents":["btree-structural-integrity-silently-erodes","btree-mutation-fsync-is-asymmetric"],"label":"Fsync asymmetry protects the values but not the tree shape, while the tree shape degrades monotonically — durability effort is precisely misallocated"}]}}