---
title: Developer FAQ
sidebarTitle: FAQ
---

This page summarizes some of the most common questions for developers building on The Graph.

## Subgraph Related

### 1. What is a Subgraph?

A Subgraph is a custom API built on blockchain data. Subgraphs are queried using the GraphQL query language and are deployed to a Graph Node using The Graph CLI. Once deployed and published to The Graph's decentralized network, Indexers process Subgraphs and make them available for Subgraph consumers to query.

### 2. What is the first step to create a Subgraph?

To successfully create a Subgraph, you will need to install The Graph CLI. Review the [Quick Start](/subgraphs/quick-start/) to get started. For detailed information, see [Creating a Subgraph](/developing/creating-a-subgraph/).

### 3. Can I still create a Subgraph if my smart contracts don't have events?

It is highly recommended that you structure your smart contracts to have events associated with data you are interested in querying. Event handlers in the Subgraph are triggered by contract events and are the fastest way to retrieve useful data.

If the contracts you work with do not contain events, your Subgraph can use call and block handlers to trigger indexing. However, this is not recommended, as performance will be significantly slower.

### 4. Can I change the GitHub account associated with my Subgraph?

No. Once a Subgraph is created, the associated GitHub account cannot be changed. Please make sure to carefully consider this before creating your Subgraph.

### 5. How do I update a Subgraph on mainnet?

You can deploy a new version of your Subgraph to Subgraph Studio using the CLI. This action maintains your Subgraph private, but once you’re happy with it, you can publish to Graph Explorer. This will create a new version of your Subgraph that Curators can start signaling on.

### 6. Is it possible to duplicate a Subgraph to another account or endpoint without redeploying?

You have to redeploy the Subgraph, but if the Subgraph ID (IPFS hash) doesn't change, it won't have to sync from the beginning.

### 7. How do I call a contract function or access a public state variable from my Subgraph mappings?

Take a look at `Access to smart contract` state inside the section [AssemblyScript API](/subgraphs/developing/creating/graph-ts/api/#access-to-smart-contract-state).

### 8. Can I import `ethers.js` or other JS libraries into my Subgraph mappings?

Not currently, as mappings are written in AssemblyScript.

One possible alternative solution to this is to store raw data in entities and perform logic that requires JS libraries on the client.

### 9. When listening to multiple contracts, is it possible to select the contract order to listen to events?

Within a Subgraph, the events are always processed in the order they appear in the blocks, regardless of whether that is across multiple contracts or not.

### 10. How are templates different from data sources?

Templates allow you to create data sources quickly, while your Subgraph is indexing. Your contract might spawn new contracts as people interact with it. Since you know the shape of those contracts (ABI, events, etc.) upfront, you can define how you want to index them in a template. When they are spawned, your Subgraph will create a dynamic data source by supplying the contract address.

Check out the "Instantiating a data source template" section on: [Data Source Templates](/developing/creating-a-subgraph/#data-source-templates).

### 11. Is it possible to set up a Subgraph using `graph init` from `graph-cli` with two contracts? Or should I manually add another dataSource in `subgraph.yaml` after running `graph init`?

Yes. On `graph init` command itself you can add multiple dataSources by entering contracts one after the other.

You can also use `graph add` command to add a new dataSource.

### 12. In what order are the event, block, and call handlers triggered for a data source?

Event and call handlers are first ordered by transaction index within the block. Event and call handlers within the same transaction are ordered using a convention: event handlers first then call handlers, each type respecting the order they are defined in the manifest. Block handlers are run after event and call handlers, in the order they are defined in the manifest. Also these ordering rules are subject to change.

When new dynamic data source are created, the handlers defined for dynamic data sources will only start processing after all existing data source handlers are processed, and will repeat in the same sequence whenever triggered.

### 13. How do I make sure I'm using the latest version of graph-node for my local deployments?

You can run the following command:

```sh
docker pull graphprotocol/graph-node:latest
```

> Note: docker / docker-compose will always use whatever graph-node version was pulled the first time you ran it, so make sure you're up to date with the latest version of graph-node.

### 14. What is the recommended way to build "autogenerated" ids for an entity when handling events?

If only one entity is created during the event and if there's nothing better available, then the transaction hash + log index would be unique. You can obfuscate these by converting that to Bytes and then piping it through `crypto.keccak256` but this won't make it more unique.

### 15. Can I delete my Subgraph?

Yes, you can [delete](/subgraphs/developing/managing/deleting-a-subgraph/) and [transfer](/subgraphs/developing/managing/transferring-a-subgraph/) your Subgraph.

## Network Related

### 16. What networks are supported by The Graph?

You can find the list of the supported networks [here](/supported-networks/).

### 17. Is it possible to differentiate between networks (mainnet, Sepolia, local) within event handlers?

Yes. You can do this by importing `graph-ts` as per the example below:

```javascript
import { dataSource } from '@graphprotocol/graph-ts'

dataSource.network()
dataSource.address()
```

### 18. Do you support block and call handlers on Sepolia?

Yes. Sepolia supports block handlers, call handlers and event handlers. It should be noted that event handlers are far more performant than the other two handlers, and they are supported on every EVM-compatible network.

## Indexing & Querying Related

### 19. Is it possible to specify what block to start indexing on?

Yes. `dataSources.source.startBlock` in the `subgraph.yaml` file specifies the number of the block that the dataSource starts indexing from. In most cases, we suggest using the block where the contract was created: [Start blocks](/developing/creating-a-subgraph/#start-blocks)

### 20. What are some tips to increase the performance of indexing? My Subgraph is taking a very long time to sync

Yes, you should take a look at the optional start block feature to start indexing from the block where the contract was deployed: [Start blocks](/developing/creating-a-subgraph/#start-blocks)

### 21. Is there a way to query the Subgraph directly to determine the latest block number it has indexed?

Yes! Try the following command, substituting "organization/subgraphName" with the organization under it is published and the name of your subgraph:

```sh
curl -X POST -d '{ "query": "{indexingStatusForCurrentVersion(subgraphName: \"organization/subgraphName\") { chains { latestBlock { hash number }}}}"}' https://api.thegraph.com/index-node/graphql
```

### 22. Is there a limit to how many objects The Graph can return per query?

By default, query responses are limited to 100 items per collection. If you want to receive more, you can go up to 1000 items per collection and beyond that, you can paginate with:

```graphql
someCollection(first: 1000, skip: <number>) { ... }
```

### 23. If my dapp frontend uses The Graph for querying, do I need to write my API key into the frontend directly? What if we pay query fees for users – will malicious users cause our query fees to be very high?

Currently, the recommended approach for a dapp is to add the key to the frontend and expose it to end users. That said, you can limit that key to a hostname, like _yourdapp.io_ and Subgraph. The gateway is currently being run by Edge & Node. Part of the responsibility of a gateway is to monitor for abusive behavior and block traffic from malicious clients.

## Miscellaneous

### 24. Is it possible to use Apollo Federation on top of graph-node?

Federation is not supported yet. At the moment, you can use schema stitching, either on the client or via a proxy service.

### 25. I want to contribute or add a GitHub issue. Where can I find the open source repositories?

- [graph-node](https://github.com/graphprotocol/graph-node)
- [graph-tooling](https://github.com/graphprotocol/graph-tooling)
- [graph-docs](https://github.com/graphprotocol/docs)
- [graph-client](https://github.com/graphprotocol/graph-client)
