2

I have a function that, according to the Unique ID of the car, gives me all its characteristics:

function getCarArray(uint _carId) 
        public 
        view 
        returns (uint[12] memory) 
    {
        CarData memory car = cars[_carId];

        uint[12] memory carInfo;

        carInfo[0] = car.statusEnd;
        carInfo[1] = car.number;
        carInfo[2] = car.load;
        carInfo[3] = car.capacity;
        carInfo[4] = car.region;
        carInfo[5] = car.status;
        carInfo[6] = car.abrasion;
        carInfo[7] = car.repairs;
        carInfo[8] = uint(car.currentOwner);
        carInfo[9] = uint(car.movingTo);
        carInfo[10] = car.resourceType;
        carInfo[11] = car.resourceAmount;

        return carInfo;
    }

When I call this method on the front end, in order to display all the cars and their characteristics, I have a very long time to process this whole. Suppose I have 1000 cars. I go through all the auto cycle

for(i=0;i<1000;i++){
     contractAddress.getCarArray(i)….
}

And then I get 1000 calls to the node, which results in a long time loading all the information.

That's the question - Is there any mechanism that will reduce the time to get all the available cars and information about them? Or on the front end side or on the Solidity side?

1

You could have a getCarsArray that returns an array of length 12*cars.length and populates all the cars' data in it. Also, if you use the v2 abi encoder, you can just return an array of structs I believe, which will be much cleaner to work with.

This will make it so you only have to wait for the response of 1 eth_call.

  • Thank you. They say that it is not necessary to use experimental features (Abi Encoder V2) on live deployments. ethereum.stackexchange.com/a/64566/44887 And you can read more explain how "returns an array of length 12*cars.length and populates all the cars' data in it"? Don't understand how to implement it – I. Simonov Feb 20 at 15:27
  • It's not recommended, no, but the ABIEncoderV2 has been usable and stable (also supported in the latest versions of web3.js) for over 6 months. We've been using it in production at totle.com. After further thought, I realized that you also can't return a dynamic array without the ABIEncoderV2, which would be required to return all cars, assuming the number of cars changes . You can instead do pagination to return the cars in large chunks (say 10 or 100) to cut down on eth_calls. – flygoing Feb 20 at 15:33
  • I understand what you're talking about! But I don't understand how can I modify your code to return information about 10 cars in 1 function call getCarsArray – I. Simonov Feb 20 at 15:45
1

Solved my problem with this code

function getCarsInfo()
    public view
    returns (uint[] memory)
{   
    uint i;
    uint j = 0;
    uint carCount = 10; 
    uint[] memory carIdArray = new uint[](carCount);
    for (i = 0; i < carCount; i++){
        carIdArray[j] = i;
        j++;
    }

    uint lengthArray = carCount*12;
    uint[] memory allCarInfoBigArray = new uint[](lengthArray);
    i=0;
    for (j = 0; j < carIdArray.length; j++) {
        CarData memory car = cars[carIdArray[j]];

        allCarInfoBigArray[i] = car.statusEnd;
        allCarInfoBigArray[i+1] = car.number;
        allCarInfoBigArray[i+2] = car.load;
        allCarInfoBigArray[i+3] = car.capacity;
        allCarInfoBigArray[i+4] = car.region;
        allCarInfoBigArray[i+5] = car.status;
        allCarInfoBigArray[i+6] = car.abrasion;
        allCarInfoBigArray[i+7] = car.repairs;
        allCarInfoBigArray[i+8] = uint(car.currentOwner);
        allCarInfoBigArray[i+9] = uint(car.movingTo);
        allCarInfoBigArray[i+10] = car.resourceType;
        allCarInfoBigArray[i+11] = car.resourceAmount;
        i = i + 12;
    }
    return allCarInfoBigArray;
}

At the output I get an array in which all the parameters of each car are written in order

    allCarInfoBigArray = [
        1550702844,0,0,20,1,0,0,0,address,0,0,0,
        1550702849,1,0,20,1,0,0,0,address,0,0,0,
        1550702851,2,0,20,1,0,0,0,address,0,0,0
        1550702855,3,0,20,1,0,0,0,address,0,0,0
        1550702860,4,0,20,1,0,0,0,address,0,0,0
        1550702865,5,0,20,1,0,0,0,address,0,0,0
        1550702870,6,0,20,1,0,0,0,address,0,0,0
        1550702875,7,0,20,1,0,0,0,address,0,0,0
        1550702880,8,0,20,1,0,0,0,address,0,0,0
        1550702885,9,0,20,1,0,0,0,address,0,0,0]
0

The fastest way to do this would be to create your own block explorer that stores relevant data in a DB. Your front end would read the data from.the DB (as opposed to the blockchain).

To do this, you would create a worker that watches for changes on your contract. It would store the relevant changes in your off-chain database, and index relevant items. The front end can read the values from the database much quicker than from.the distributed network.

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