Subgraph Development Guide

Blockchain Events → Subgraph Indexer → GraphQL API
(Swap, Transfer,    (Processes,        (Fast queries,
 Mint, Burn)         aggregates)        relationships)

┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│  1. Schema       │    │  2. Mappings     │    │  3. Manifest     │
│  (GraphQL types) │    │  (Event handlers)│    │  (subgraph.yaml) │
│                  │    │                  │    │                  │
│  type Token {    │    │  handleSwap(e) { │    │  dataSources:    │
│    id: ID!       │    │    // process    │    │    - name: Pool  │
│    symbol: String│    │    // and save   │    │      source:     │
│    volume: BigInt│    │  }              │    │        abi: Pool  │
│  }              │    │                  │    │        address:   │
└─────────────────┘    └─────────────────┘    └─────────────────┘

type Token @entity {
  id: ID!                       # Contract address
  symbol: String!
  name: String!
  decimals: Int!
  totalSupply: BigInt!
  transferCount: BigInt!
  holderCount: BigInt!
}

type Transfer @entity {
  id: ID!                       # tx hash + log index
  token: Token!
  from: Bytes!
  to: Bytes!
  value: BigDecimal!
  timestamp: BigInt!
  blockNumber: BigInt!
}

type Account @entity {
  id: ID!                       # Wallet address
  balances: [AccountBalance!]! @derivedFrom(field: "account")
}

type AccountBalance @entity {
  id: ID!                       # account-token
  account: Account!
  token: Token!
  balance: BigDecimal!
}

specVersion: 0.0.5
schema:
  file: ./schema.graphql

dataSources:
  - kind: ethereum
    name: USDC
    network: arbitrum-one
    source:
      address: "0xaf88d065e77c8cC2239327C5EDb3A432268e5831"
      abi: ERC20
      startBlock: 100000000
    mapping:
      kind: ethereum/events
      apiVersion: 0.0.7
      language: wasm/assemblyscript
      entities:
        - Token
        - Transfer
        - Account
      abis:
        - name: ERC20
          file: ./abis/ERC20.json
      eventHandlers:
        - event: Transfer(indexed address,indexed address,uint256)
          handler: handleTransfer
      file: ./src/mapping.ts

import { Transfer as TransferEvent } from "../generated/USDC/ERC20"
import { Token, Transfer, Account, AccountBalance } from "../generated/schema"
import { BigInt, BigDecimal } from "@graphprotocol/graph-ts"

export function handleTransfer(event: TransferEvent): void {
  // Load or create token
  let token = Token.load(event.address.toHexString())
  if (token == null) {
    token = new Token(event.address.toHexString())
    token.symbol = "USDC"
    token.name = "USD Coin"
    token.decimals = 6
    token.totalSupply = BigInt.fromI32(0)
    token.transferCount = BigInt.fromI32(0)
    token.holderCount = BigInt.fromI32(0)
  }
  token.transferCount = token.transferCount.plus(BigInt.fromI32(1))
  token.save()

  // Create transfer entity
  let transfer = new Transfer(
    event.transaction.hash.toHexString() + "-" + event.logIndex.toString()
  )
  transfer.token = token.id
  transfer.from = event.params.from
  transfer.to = event.params.to
  transfer.value = event.params.value.toBigDecimal().div(
    BigDecimal.fromString("1000000") // 6 decimals
  )
  transfer.timestamp = event.block.timestamp
  transfer.blockNumber = event.block.number
  transfer.save()
}

{
  tokens(first: 10, orderBy: transferCount, orderDirection: desc) {
    id
    symbol
    transferCount
  }
}

{
  transfers(
    first: 20
    orderBy: timestamp
    orderDirection: desc
    where: { value_gt: "100000" }
  ) {
    from
    to
    value
    timestamp
    token { symbol }
  }
}

{
  account(id: "0x1234...") {
    balances {
      token { symbol }
      balance
    }
  }
}

# Install CLI
npm install -g @graphprotocol/graph-cli

# Initialize
graph init --studio my-subgraph

# Authenticate
graph auth --studio YOUR_DEPLOY_KEY

# Build + Deploy
graph codegen
graph build
graph deploy --studio my-subgraph

# Docker Compose
docker-compose up graph-node postgres ipfs

# Deploy to local
graph create --node http://localhost:8020/ my-subgraph
graph deploy --node http://localhost:8020/ my-subgraph