update

internal/db/db.go

@@ -43,23 +43,35 @@ func Open(driver, dsn string) (*DB, error) {
 		sqlDriverName = name
 	}
 
+	if d == "sqlite" {
+		// Set these as mattn/go-sqlite3 DSN params, not a post-open PRAGMA
+		// Exec: with more than one pooled connection, each new physical
+		// connection database/sql opens is a fresh SQLite connection that
+		// does NOT inherit a PRAGMA set on a different one (journal_mode is
+		// the one exception — it's persisted in the DB file itself).
+		// _foreign_keys and _busy_timeout must be per-connection, so they
+		// have to ride in the DSN to apply to every connection the pool
+		// ever opens, not just the first.
+		sep := "?"
+		if strings.Contains(dsn, "?") {
+			sep = "&"
+		}
+		dsn += sep + "_journal_mode=WAL&_foreign_keys=on&_busy_timeout=5000"
+	}
+
 	sqlDB, err := sql.Open(sqlDriverName, dsn)
 	if err != nil {
 		return nil, fmt.Errorf("opening database: %w", err)
 	}
 
 	if d == "sqlite" {
-		// SQLite doesn't handle concurrent writers well — serialize via single conn.
-		sqlDB.SetMaxOpenConns(1)
-		if _, err := sqlDB.Exec("PRAGMA journal_mode=WAL"); err != nil {
-			return nil, fmt.Errorf("enabling WAL mode: %w", err)
-		}
-		if _, err := sqlDB.Exec("PRAGMA foreign_keys=ON"); err != nil {
-			return nil, fmt.Errorf("enabling foreign keys: %w", err)
-		}
-		if _, err := sqlDB.Exec("PRAGMA busy_timeout=5000"); err != nil {
-			return nil, fmt.Errorf("setting busy timeout: %w", err)
-		}
+		// WAL mode already lets SQLite itself handle concurrent readers +
+		// one writer (with _busy_timeout above covering writer contention) —
+		// a small pool, not a single shared connection, so concurrent
+		// requests across SMTP/IMAP/webmail/admin/etc. aren't all serialized
+		// through one connection for no reason.
+		sqlDB.SetMaxOpenConns(4)
+		sqlDB.SetMaxIdleConns(4)
 	}
 
 	if err := sqlDB.Ping(); err != nil {