How to build a subgraph from scratch

npm install -g @graphprotocol/graph-cli

mkdir katana-blocks
cd katana-blocks

npm init -y

npm install --save-dev @graphprotocol/graph-ts
npm install --save-dev assemblyscript

specVersion: 0.0.5
description: Blocks indexer for Katana
schema:
  file: ./schema.graphql

dataSources:
  # We declare a contract data source so we can attach a blockHandler.
  # The "Dummy" ABI is unused but required by the manifest when kind=ethereum/contract.
  - kind: ethereum/contract
    name: KatanaBlocks
    network: katana
    source:
      address: "0x0000000000000000000000000000000000000000"  # not used
      abi: Dummy
      startBlock: 1
    mapping:
      kind: ethereum/events
      apiVersion: 0.0.7
      language: wasm/assemblyscript
      entities:
        - Block
      abis:
        - name: Dummy
          file: ./abis/Dummy.json
      # This is the key: run our handler every block
      blockHandlers:
        - handler: handleBlock
      file: ./mappings/blocks.ts

type Block @entity(immutable: true) {
  id: ID!            # we will use the block number as the ID
  number: BigInt!
  timestamp: BigInt!
  hash: Bytes!
  parentHash: Bytes!
}

import { Block as BlockEntity } from "../generated/schema";
import { ethereum } from "@graphprotocol/graph-ts";

export function handleBlock(block: ethereum.Block): void {
  // Use block number as the stable ID
  let id = block.number.toString();

  let entity = new BlockEntity(id);
  entity.number = block.number;
  entity.timestamp = block.timestamp;
  entity.hash = block.hash;
  entity.parentHash = block.parentHash;
  entity.save();
}

katana-blocks/
├─ abis/
│  └─ Dummy.json          
├─ mappings/
│  └─ blocks.ts
├─ schema.graphql
└─ subgraph.yaml

graph codegen

graph build

graph deploy <graph-name> --node  https://subgraph.api.ormilabs.com/deploy --ipfs https://subgraph.api.ormilabs.com/ipfs --deploy-key <API key>

{
  blocks(first: 5) {
    id
    number
    timestamp
    parentHash
  }
}