We have already:

static void
pk_transaction_db_init (PkTransactionDb *tdb)
{
	gboolean create_file;
	const gchar *statement;
	gint rc;

	g_return_if_fail (tdb != NULL);
	g_return_if_fail (PK_IS_TRANSACTION_DB (tdb));

	tdb->priv = PK_TRANSACTION_DB_GET_PRIVATE (tdb);

	/* if the database file was not installed (or was nuked) recreate it */
	create_file = g_file_test (PK_TRANSACTION_DB_FILE, G_FILE_TEST_EXISTS);

	pk_debug ("trying to open database '%s'", PK_TRANSACTION_DB_FILE);
	rc = sqlite3_open (PK_TRANSACTION_DB_FILE, &tdb->priv->db);
	if (rc) {
		pk_warning ("Can't open database: %s\n", sqlite3_errmsg (tdb->priv->db));
		sqlite3_close (tdb->priv->db);
		return;
	} else {
		if (create_file == FALSE) {
			statement = "CREATE TABLE transactions ("
				    "transaction_id TEXT primary key,"
				    "timespec TEXT,"
				    "duration INTEGER,"
				    "succeeded INTEGER DEFAULT 0,"
				    "role TEXT,"
				    "data TEXT,"
				    "description TEXT);";
			sqlite3_exec (tdb->priv->db, statement, NULL, NULL, NULL);
		}
	}

	/* we might be running an old database, recreate */
	pk_transaction_db_create_table_last_action (tdb);
}

So I think all we need to do is error out on the pk_warning ("Can't open database... string? What do you think?

Erroring out is probably the best solution.

It seems as if the rest of the code cannot handle a non-existing database. I get random crashes when ending packagekitd with Ctrl-C.

Yup, I've added a load of checks in 02c8fd68a96cf5f5aece013afee94ecbb1e5752c

Does the daemon now do what you expect?

Looks good now.