Cheapest way to access and modify a struct - solidity

Question

I am using solidity 0.8.10.
In my contract I have a state variable struct:
struct Product {
uint id_prod;
address payable producer_addr;
address payable owner_addr;
bool onSale;
}
and a state variable array of products:
Product[] public ProductList;
and a function that allows to modify the attributes of the product. Nothing really complex.
Considering the cost in deploying and using the contract, I think there are two ways of changing the attributes of the product.
Solution 1, by using a storage variable:
Product storage _product = ProductList[_id_product];
_product.owner_addr = payable(msg.sender);
_product.onSale = false;
Solution 2, without a storage variable:
ProductList[_id_product].owner_addr = payable(msg.sender);
ProductList[_id_product].onSale = false;
Which solution is the cheapest, cleanest, most advisable?

Answer 1

First, the numbers:
I deployed a similar contract to yours and called each function. Although implementations can vary,
The transaction costs were:
Solution 1: 28785 gas
Solution 2: 28985 gas
And, deployment costs were:
Solution 1: 275180
Solution 2: 281006
Solution 2 uses 2 sload and 2 sstore operations. It loads from storage each time you want to access the data, and writes to storage each time you assign new value.
Solution 1 uses a storage pointer. So we sload only once and than use the reference.
You can see from the transaction cost differences, that the difference is 200 gas and a single sload operation uses 200 gas as well.
So, both in terms of readability(imho), transaction cost and deployment cost; solution 1 was more efficient. And the more fields you use, the more efficient the solution 1 will become.