Method movePrevious

fdbserver/KeyValueStoreSQLite.actor.cpp:760–764

		valid = !empty;
	}
	void movePrevious() {
		int empty = 1;
		db.checkError("BtreePrevious", sqlite3BtreePrevious(cursor, &empty));
		valid = !empty;
	}
	int size() {
		int64_t size;
		db.checkError("BtreeKeySize", sqlite3BtreeKeySize(cursor, (i64*)&size));