Syncthing on SQLite -- help test!

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@Martchus

On Android SQLite seems to have one advantage over leveldb: When moving the Syncthing database to the SD-card one so far wasn’t able to start Syncthing because it couldn’t create the database lock file (even when staying within the private app folder within the SD-card). In both cases (SD-card and internal storage) Android uses FUSE. So I guess the problem is that the actual underlying filesystem on the SD-card (e.g. exFAT) doesn’t support locking in the way leveldb requires it. With SQLite3 this problem seems no longer apparent. (I’m only wondering whether concurrent accesses are handles as well by SQLite then.)

That’s probably caused by syncthing running SQLite in WAL mode. With WAL, SQLite synchronizes by sharing memory between processes (if needed) instead of using POSIX advisory locks (flocks) [which SQLite can also use].