Must journal_mode be set every time? #1444

Yes.

https://www.sqlite.org/pragma.html#pragma_journal_mode

This pragma queries or sets the journal mode for databases associated with the current database connection.

(emphasis mine)

Edit: sorry, that's not entirely true

The WAL journaling mode uses a write-ahead log instead of a rollback journal to implement transactions. The WAL journaling mode is persistent; after being set it stays in effect across multiple database connections and after closing and reopening the database. A database in WAL journaling mode can only be accessed by SQLite version 3.7.0 (2010-07-21) or later.

However, I would only trust this if you know that the database file hasn't been opened with another mode in between. So it's safe to just always set it.