You're sort of right in that a B-tree is not a good data structure for logs given that append-only files are perfect for logs. But the point of using an RDBMS for logs is to be able to a) index the logs, b) provide a great search facility for logs. Perhaps a better design would be a virtual table plugin for SQLite3 that allows one to use log files as tables, then index and search them with SQLite3, but if one lacks the time to investigate that approach then oe can't be faulted for using SQLite3 directly.