How to Build and Deploy a Subgraph with The Graph Protocol

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The Graph is a tool that helps apps quickly access blockchain data. It uses a technology called GraphQL to pull data efficiently. Developers use it during blockchain app development to build faster and more reliable blockchain apps. It organizes blockchain data into something called subgraphs, making it easier to handle. This tool supports several blockchains, enhancing its usefulness for developers.

Advantages

• Speed: It speeds up how quickly apps can access blockchain data.
• Efficiency: It makes data retrieval more efficient using GraphQL.
• Simplicity: Organizes data into subgraphs, which are easier for developers to manage.
• Flexibility: Supports multiple blockchains, giving developers more options.
• Reliability: Enhances the stability and reliability of decentralized applications.

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Steps to create and deploy subgraph

Install Graph CLI:

Command:

yarn global add @graphprotocol/graph-cli` or `npm install -g @graphprotocol/graph-cli`

This installs the necessary tools to create and manage subgraphs.

Initialize Your Subgraph:

Command: 

`graph init --from-example <GITHUB_USER>/<SUBGRAPH_NAME>`

This sets up a new subgraph directory with starter files based on a template.

Define subgraph.yaml:

 Example

  yaml
  specVersion: 0.0.2
  description: "Example subgraph"
  repository: "https://github.com/example/repo"
  dataSources:
    - kind: ethereum/contract
      name: ContractName
      source:
        address: "0x..."
        abi: ContractABI
      mapping:
        kind: ethereum/events
        apiVersion: 0.0.4
        language: wasm/assemblyscript
        entities:
          - EntityName
        abis:
          - name: ContractABI
            file: ./abis/ContractABI.json
        eventHandlers:
          - event: Transfer(address,address,uint256)
            handler: handleTransfer
        file: ./src/mapping.ts
 

 This file configures your subgraph, defining which blockchain events it listens to and how they map to the data entities.

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Create the GraphQL Schema:

 File: schema.graphql

Example content:

  ```graphql
  type Transfer @entity {
    id: ID!
    from: Bytes!
    to: Bytes!
    value: BigInt!
  }
  ```

This defines the data structures that your subgraph will store and make queryable.

Write AssemblyScript Mappings:

File: `src/mapping.ts`

Example function:

  ```typescript
  import { BigInt } from "@graphprotocol/graph-ts"
  import { Transfer } from "../generated/Contract/Contract"

  export function handleTransfer(event: Transfer): void {
    let transfer = new Transfer(event.params.from, event.params.to, event.params.value)
    transfer.save()
  }
  ```

This script processes incoming blockchain events and translates them into entities defined in the GraphQL schema.

Deploy Your Subgraph:

Command:

`graph deploy --product hosted-service <GITHUB_USER>/<SUBGRAPH_NAME>`

This uploads your subgraph to The Graph's hosted service, making it available for queries.

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Conclusion

In conclusion, The Graph Protocol is a powerful tool for developers looking to build and deploy efficient, reliable, and scalable blockchain applications. By using GraphQL to quickly access and manage blockchain data, and organizing it into subgraphs, developers can significantly enhance the performance and stability of their decentralized applications. With support for multiple blockchains, The Graph provides flexibility and a robust solution for a variety of use cases. Following the steps outlined"”installing the Graph CLI, initializing your subgraph, defining the subgraph.yaml, creating a GraphQL schema, writing AssemblyScript mappings, and deploying your subgraph"”will enable you to leverage the full potential of The Graph Protocol, streamlining your development process and improving your application's overall functionality. Connect with our skilled blockchain developers for a quick consultation regarding your blockchain or crypto project.