{"id":"lsm-compaction-is-full-merge","text":"`compact()` merges all SSTables into a single new SSTable (size-tiered, single-level), not incremental or leveled — simpler but with higher space amplification.","truth_value":"IN","source":"entries/2026/05/28/log-structured-merge-tree-lsm.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{"example":"def compact(self):\n    entries = {}\n    for sst in self._sstables:\n        for key, value in sst.scan():\n            entries[key] = value  # newer overwrites older\n    # write single new SSTable from merged entries"},"explanation":{"steps":[{"node":"lsm-compaction-is-full-merge","truth_value":"IN","reason":"premise"}]}}