Creating a Query

When a user requests data using tipQuery or when a reporter submits data using submitValue, they have to input both the queryId and queryData. The queryData tells reporters how to fulfill the data query, while also informing voters how to verify the data in a dispute. The queryId is defined as the keccak256 hash of the queryData field.

In order to query the Tellor oracle you'll need to first generate the queryData and its hash, the queryId.

Getting a Query ID and Query Data

Use the tools below to generate a queryId and queryData:

Get A Query ID

If the existing Query Types don't fit your needs you'll need to define a new one.

Creating a new Query Type

To create a new Query Type, or specification, for custom data you need from Tellor oracles, there's two options:

• Make an issue like this and the Tellor team will help with the next steps.

• Fork this repository and make a pull request for a new Query type in ./types using this template.

To add a new data type to Tellor, you'll just need to define a new queryType . This is how you form a question so that Tellor reporters know exactly what data is being requested. You'll need to determine three things: a unique queryType name, inputs, and outputs. So let's say you want a query for getting the price of any asset in any currency. In human-readable form, your question could look like this:

What is the price of asset in currency ?

You might formally define your query like this:

Name: SpotPrice

Inputs:

1. asset (string): Asset ID (e.g. btc)

2. currency (string): Selected currency (e.g. usd)

Outputs:

1. price (uint256)

- abi_type: ufixed256x18 (18 decimals of precision)

- packed: false

Once Tellor reporters are submitting your new queryType on chain, you can retrieve your desired data with the help of UsingTellor, which is a helper contract that provides various Tellor data getters. You'll first put your question in queryData format, which means encoding your queryType name and arguments into bytes (see below). You'll then need to get a queryId, which is the bytes32 unique identifier for each Tellor data feed. The queryId is defined as the keccak256 hash of queryData. Once you know the queryId you'll be able to retrieve your data.

In Solidity, your contract can get data like this:

contract ExampleContract is UsingTellor {

    // _tellorAddress is the address of the Tellor oracle
    constructor(address payable _tellorAddress) UsingTellor(_tellorAddress) {}

    function getSpotPrice(string memory _asset, string memory _currency) external view returns(uint256) {
      bytes memory _queryData = abi.encode("SpotPrice", abi.encode(_asset, _currency));
      bytes32 _queryId = keccak256(_queryData);
      bool _ifRetrieve, bytes memory _value, uint256 _timestampRetrieved) = getDataBefore(_queryId, block.timestamp - 2 hours);
      if (!ifRetrieve) return 0;
      return abi.decode(_value, (uint256));
    }
}

Example QueryData and QueryID

If you input btc and usd, respectively, the queryData would be:

0x00000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000000953706f745072696365000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000c0000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000003627463000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000037573640000000000000000000000000000000000000000000000000000000000

and the queryId would be

0xa6f013ee236804827b77696d350e9f0ac3e879328f2a3021d473a0b778ad78ac

Feel free to start building a query now and integrating it into your project. When you reach the later stages of building your project, add an issue to Tellor's dataSpecs repository so that data reporters know how to fulfill your query. Feel free to reach out to the Tellor team for assistance, and happy building!