LSM 06-07: Compaction and Levels

The Discord case-study board on a message store whose trouble came from the thing this lesson builds. Part of the LSM series, Build Your Own LSM Tree.

Before you start. This series builds a small copy of a storage engine that never edits a file in place. LSM 03-04: Table Files and the Sparse Index made flushing safe and lookups cheap per file, and LSM 05: The Bloom Filter let a lookup skip files that cannot hold a key. Neither stops the number of files growing with every flush. This lesson builds the background job that merges them, then arranges the files in levels so a lookup touches about one.