Subgraph Composition Example

This example demonstrates how to use one subgraph as a data source for another, leveraging the Sushiswap v3 subgraph on the Base chain. The setup involves two subgraphs:

1. Source Subgraph: Tracks event data as entities.
2. Dependent Subgraph: Uses the source subgraph as a data source.

These subgraphs are located in the source and dependent directories, respectively.

The source subgraph is a basic event-tracking subgraph that records events emitted by relevant contracts. The dependent subgraph references the source subgraph as a data source, using the entities from the source as triggers. While the source subgraph is a standard subgraph, the dependent subgraph utilizes the subgraph composition feature.

Source Subgraph

The source subgraph tracks events from the Sushiswap v3 subgraph on the Base chain. This subgraph’s configuration file is located in the source/subgraph.yaml.

Dependent Subgraph

The dependent subgraph, located in the dependent/subgraph.yaml, specifies the source subgraph as a data source. This subgraph uses entities from the source as triggers, defining specific actions in response to entity changes.

To set the source subgraph as a data source in the dependent subgraph, include the following in subgraph.yaml:

specVersion: 1.3.0
schema:
  file: ./schema.graphql
dataSources:
  - kind: subgraph
    name: Factory
    network: scroll
    source:
      address: 'QmdXu8byAFCGSDWsB5gMQjWr6GUvEVB7S1hemfxNuomerz'
      startBlock: 82522

Here, source.address refers to the Deployment ID of the source subgraph, and startBlock specifies the block from which indexing should begin.

Defining Handlers

Below is an example of defining handlers in the dependent subgraph:

export function handleInitialize(trigger: EntityTrigger<Initialize>): void {
  if (trigger.operation === EntityOp.Create) {
    let entity = trigger.data;
    let poolAddressParam = Address.fromBytes(entity.poolAddress);

    // Update pool sqrt price and tick
    let pool = Pool.load(poolAddressParam.toHexString()) as Pool;
    pool.sqrtPrice = entity.sqrtPriceX96;
    pool.tick = BigInt.fromI32(entity.tick);
    pool.save();

    // Update token prices
    let token0 = Token.load(pool.token0) as Token;
    let token1 = Token.load(pool.token1) as Token;

    // Update ETH price in USD
    let bundle = Bundle.load('1') as Bundle;
    bundle.ethPriceUSD = getEthPriceInUSD();
    bundle.save();

    updatePoolDayData(entity);
    updatePoolHourData(entity);

    // Update derived ETH price for tokens
    token0.derivedETH = findEthPerToken(token0);
    token1.derivedETH = findEthPerToken(token1);
    token0.save();
    token1.save();
  }
}

In this example, the handleInitialize function is triggered when a new Initialize entity is created in the source subgraph, passed as EntityTrigger<Initialize>. The handler updates the pool and token entities based on data from the new Initialize entity.

EntityTrigger has three fields:

1. operation: Specifies the operation type, which can be Create, Modify, or Remove.
2. type: Indicates the entity type.
3. data: Contains the entity data.

Developers can then determine specific actions for the entity data based on the operation type.