sqlite

func DSN ¶

func DSN(path string) string

DSN returns the data source name to open the database at path with, for sqlitedriver.SqliteDB.Open. Open the database you hand to New with it:

sdb := sqlitedriver.New()
err := sdb.Open(ctx, sqlite.DSN("tether.db"))

database/sql pools connections and every pooled connection has its own settings, so the DSN is the one place that reaches all of them. Grove's driver runs PRAGMA foreign_keys=ON once at Open, on whichever connection it gets, and sets no busy timeout. DSN adds three settings, applied by modernc.org/sqlite to each connection it opens:

• busy_timeout: a write waits up to BusyTimeout for the write lock instead of failing at once with SQLITE_BUSY. Device and tenant writes arrive from connection handlers and the admin API at the same time.
• foreign_keys: on for every connection. Tether's tables declare no foreign keys, so this only matters to tables a host adds beside them.
• _txlock=immediate: transactions take the write lock at BEGIN. SQLite skips the busy timeout when a transaction that has already read tries to write, and fails at once.

path is a file name or a file: URI. Query parameters already on it are kept, and so is any of the three settings it already sets: the caller's _txlock, busy_timeout or foreign_keys wins, and DSN adds only the ones that are missing. If you open the database some other way, such as from a grove extension's config, put the same three parameters on that DSN.