Lesson 4: Data Mutation Example
Lesson 4: Data Mutation Example
This lesson focuses on data mutation example. We will alter the code by adding Collator.Left property to the Collator entity in schema.graphql. It would require from us to regenerate associated typescript with yarn codegen and updating project.yaml and mappingHandlers.ts files as well.
Changing the Project
Note
In this lesson we will continue changing the code.
Manifest
First, let's add a new handler collatorLeft to project.yaml.
- handler: collatorLeft
kind: substrate/CallHandler
filter:
module: parachainStaking
method: leaveCandidates
Your entire Manifest file should look like this:
specVersion: 1.0.0
name: moonbeam-evm-starter
version: 0.0.1
runner:
node:
name: "@subql/node"
version: ">=0.35.0"
query:
name: "@subql/query"
version: ">=0.16.0"
description: Moonbeam / SubQuery Course — Building dApps with the help of SubQuery
repository: "https://github.com/subquery/tutorials-frontier-evm-starter"
schema:
file: ./schema.graphql
network:
chainId: "0x401a1f9dca3da46f5c4091016c8a2f26dcea05865116b286f60f668207d1474b"
endpoint: "wss://moonriver.api.onfinality.io/public-ws"
dictionary: "https://api.subquery.network/sq/subquery/moonriver-dictionary"
chaintypes:
file: ./dist/chaintypes.js
dataSources:
- kind: substrate/FrontierEvm
startBlock: 424026
processor:
file: ./node_modules/@subql/frontier-evm-processor/dist/bundle.js
options:
abi: erc20
address: "0x6bd193ee6d2104f14f94e2ca6efefae561a4334b"
assets:
erc20:
file: ./erc20.abi.json
mapping:
file: ./dist/index.js
handlers:
- handler: handleFrontierEvmEvent
kind: substrate/FrontierEvmEvent
filter:
topics:
- "Transfer(address indexed from,address indexed to,uint256 value)"
- null
- null
- null
- handler: handleFrontierEvmCall
kind: substrate/FrontierEvmCall
filter:
function: "approve(address to,uint256 value)"
- kind: substrate/Runtime
startBlock: 69218
mapping:
file: "./dist/index.js"
handlers:
- handler: collatorJoined
kind: substrate/EventHandler
filter:
module: parachainStaking
method: JoinedCollatorCandidates
- handler: collatorLeft
kind: substrate/CallHandler
filter:
module: parachainStaking
method: leaveCandidates
Note
Find more information about Polkadot specific methods in Polkadot Explorer.
Schema GraphQl
Next, we need to adjust the schema.graphql file by adding a new nonobligatory property leaveDate of type Date to the Collator entity.
Your file should look like this:
type Transaction @entity {
id: ID! # Transaction hash
value: BigInt!
to: String!
from: String!
contractAddress: String!
}
type Approval @entity {
id: ID! # Transaction hash
value: BigInt!
owner: String!
spender: String!
contractAddress: String!
}
type Collator @entity {
id: ID! # Collator address
joinedDate: Date!
leaveDate: Date
}
Mapping functions
The last thing we need to do is to add a new function collatorLeft() that corresponds with the new data handler from project.yaml file. This function needs to be responsible for handling data when collator leaves by updating the collator's property leaveDate accordingly.
// Collator Leaves
export async function collatorLeft(call: SubstrateExtrinsic): Promise<void> {
const address = call.extrinsic.signer.toString();
const collator = await Collator.get(address);
if (!collator) {
// Collator doesn't exist
} else {
collator.leaveDate = call.block.timestamp;
}
await collator.save();
}
Your entire file should look like this:
import { Approval, Collator, Transaction } from "../types";
import {
FrontierEvmEvent,
FrontierEvmCall,
} from "@subql/frontier-evm-processor";
import { BigNumber } from "ethers";
import { SubstrateEvent, SubstrateExtrinsic } from "@subql/types";
// Setup types from ABI
type TransferEventArgs = [string, string, BigNumber] & {
from: string;
to: string;
value: BigNumber;
};
type ApproveCallArgs = [string, BigNumber] & {
_spender: string;
_value: BigNumber;
};
// Create Transaction
export async function handleFrontierEvmEvent(
event: FrontierEvmEvent<TransferEventArgs>,
): Promise<void> {
const transaction = new Transaction(event.transactionHash);
transaction.value = event.args.value.toBigInt();
transaction.from = event.args.from;
transaction.to = event.args.to;
transaction.contractAddress = event.address;
await transaction.save();
}
// Create Approval
export async function handleFrontierEvmCall(
event: FrontierEvmCall<ApproveCallArgs>,
): Promise<void> {
const approval = new Approval(event.hash);
approval.owner = event.from;
approval.value = event.args._value.toBigInt();
approval.spender = event.args._spender;
approval.contractAddress = event.to;
await approval.save();
}
// Create Collator
export async function collatorJoined(event: SubstrateEvent): Promise<void> {
const address = event.extrinsic.extrinsic.signer.toString();
const collator = Collator.create({
id: address,
joinedDate: event.block.timestamp,
});
await collator.save();
}
// Collator Leaves
export async function collatorLeft(call: SubstrateExtrinsic): Promise<void> {
const address = call.extrinsic.signer.toString();
const collator = await Collator.get(address);
if (!collator) {
// Collator doesn't exist
} else {
collator.leaveDate = call.block.timestamp;
}
await collator.save();
}
Important
Remove /.data folder to reindex your data from beginning and adjust the whole database to the new Collator entity's shape. Otherwise, the indexer will start indexing data from the latest block it finished last time and your project will be missing some data of collators indexed before.
Also, remember to regerate associated typescript after any change in the schema.grapql.
Query
Open your browser and head to http://localhost:3000. Use GraphQL playground to query your data. Expand previous query by adding leaveDate property to collators:
query {
approvals (first: 5) {
nodes {
id
value
owner
spender
}
}
transactions (first: 5) {
nodes {
id
value
to: id
from: id
}
}
collators (last: 5) {
nodes {
id
joinedDate
leaveDate
}
}