Lesson 5: Explaining Reliationships in SubQuery
Lesson 5: Explaining Reliationships in SubQuery
This lesson explores entities relationships in SubQuery.
In this lesson we will create a many-to-many relationship and update Transaction entity and create Account entity. It would require regenerating associated typescript with yarn codegen and updating mappingHandlers.ts file by changing the handleFrontierEvmEvent() function.
Find out more about data reliationships in SubQuery.
Note
In this lesson we will alter the code for the last time.
Changing the Project
Schema GraphQl
To build a many-to-many relationship between Account and Transaction entity we need to update Transaction entity by adding properties related with accounts and create a brand new Account entity with specific, linking properties.
First, create a basic Account entity:
type Account @entity {
id: ID! # KeyTo establish a one-to-many reliationship link Transcation with Account by using entity's name as a property value of Transaction entity:
to: Account! # Foreign key field
from: Account! # Foreign key fieldThen, to build a many-to-many reliationship we need to create a link to Transaction entity from Account entity:
sentTransactions: [Transaction] @derivedFrom(field: "from")
receivedTransactions: [Transaction] @derivedFrom(field: "to")Note
Use @derivedFrom to create a queryable virtual field in the database. Find out more about Reverse Lookups in our documentation.
Your entire file should look like this:
type Transaction @entity {
id: ID! # Transaction hash
value: BigInt! @index
to: Account! # Foreign key field
from: Account! # Foreign key field
contractAddress: String! @index
}
type Account @entity {
id: ID! # Key
sentTransactions: [Transaction] @derivedFrom(field: "from")
receivedTransactions: [Transaction] @derivedFrom(field: "to")
}
type Approval @entity {
id: ID! # Transaction hash
value: BigInt! @index
owner: String! @index
spender: String! @index
contractAddress: String! @index
}
type Collator @entity {
id: ID! # Collator address
joinedDate: Date! @index
leaveDate: Date @index
}Mapping functions
In this file we need to change the handleFrontierEvmEvent() function that handles Transaction creation, and receives data from the chain, ensures that Account exist, and creates and saves a new Transation entity in the database.
Change your handleFrontierEvmEvent() function to achieve the following:
// Create Transaction
export async function handleFrontierEvmEvent(
event: FrontierEvmEvent<TransferEventArgs>,
): Promise<void> {
// Get data from the event
const from = event.args.from;
const to = event.args.to;
// Ensure account entities exist
const fromAccount = await Account.get(from);
if (!fromAccount) {
await new Account(from).save();
}
const toAccount = await Account.get(to);
if (!toAccount) {
await new Account(to).save();
}
// Create new transaction entity
const transaction = new Transaction(event.transactionHash);
transaction.value = event.args.value.toBigInt();
transaction.fromId = from;
transaction.toId = to;
transaction.contractAddress = event.address;
await transaction.save();
}Your entire file should look like this:
import { Account, 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> {
// Get data from the event
const from = event.args.from;
const to = event.args.to;
// Ensure account entities exist
const fromAccount = await Account.get(from);
if (!fromAccount) {
await new Account(from).save();
}
const toAccount = await Account.get(to);
if (!toAccount) {
await new Account(to).save();
}
// Create new transaction entity
const transaction = new Transaction(event.transactionHash);
transaction.value = event.args.value.toBigInt();
transaction.fromId = from;
transaction.toId = 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 accounts on the bottom:
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
}
}
accounts(first: 5) {
nodes {
id
sentTransactions {
nodes {
id
value
to: id
from: id
contractAddress
}
}
}
}
}