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Indexer /
Designing a Schema /
Types

Icon LinkTypes

Icon LinkObjects

Object types are the most commonly used type in indexer GraphQL schema. Each object type marked with an @entity directive will be converted into a SQL table. 

type Account @entity {
    id: ID!
    address: Address!
    balance: U64!
}

This Account object type from the GraphQL schema, might be used in an indexer module like so: 

extern crate alloc;
use fuel_indexer_utils::prelude::*;
 
#[indexer(manifest = "indexer.manifest.yaml")]
mod indexer_mod {
    fn handle_event(event: Event) {
        let address = Address::default();
        let balance = 0;
        let account = Account::new(address, balance);
        account.save();
    }
}

Icon LinkEnums

Enum types are simply implemented as String types. 

enum SignatureLabel {
    Multi
    Single
}

Enum types in relation to Fuel indexer's implementation are just String types used primarily to label object types. There is no other way that enum types should be used at this time. This SignatureLabel object type from the GraphQL schema, might be used in an indexer module like so: 

extern crate alloc;
use fuel_indexer_utils::prelude::*;
 
#[indexer(manifest = "indexer.manifest.yaml")]
mod indexer_mod {
    fn handle_event(event: Event) {
        let label = SignatureLabel::Multi;
        assert_eq!(label.to_string(), "SignatureLabel::Multi".to_string());
    }
}

Icon LinkUnions

Union types are unique in that any type marked as a union will be converted into an Object type, who's fields are the unique set of fields over all members of the union. 

enum TransactionLabel {
    Create
    Script
    Mint
}
 
type CreateTransaction @entity {
    id: ID!
    bytecode_length: U64!
    contract_id: ContractId!
    label: TransactionLabel!
}
 
type ScriptTransaction @entity {
    id: ID!
    maturity: U64!
    label: TransactionLabel!
}
 
type MintTransaction @entity {
    id: ID!
    metadata: Json
    label: TransactionLabel!
}
 
union Transaction = CreateTransaction | ScriptTransaction | MintTransaction

The Transaction union type above, will internally produce the following object type: 

type Transaction @entity {
    id: ID!
    bytecode_length: U64!
    contract_id: ContractId!
    label: TransactionLabel!
    maturity: U64!
    metadata: Json
}

IMPORTANT: Note the order of the fields in the derived Transaction object type: the fields are ordered according to the unique set of fields from each of the union's members.

The id, bytecode_length, contract_id, and label fields come first, from the CreateTransaction object type. Next comes the maturity field from the ScriptTransaction object - because the ScriptTransaction's id and label fiels are already a part of the derived Transaction object, courtesy of the CreateTransaction object type. Finally, comes the metadata field, as part of the MintTransaction object type. This Transaction union type from the GraphQL schema, might be used in an indexer module like so: 

extern crate alloc;
use fuel_indexer_utils::prelude::*;
 
#[indexer(manifest = "indexer.manifest.yaml")]
mod indexer_mod {
    fn handle_event(event: Event) {
        let bytecode_length = 1024;
        let contract_id = ContractId::default();
        let label = TransactionLabel::Create;
        let maturity = 10000000;
        let metadata = None;
        let transaction = Transaction::new(bytecode_length, contract_id, label, maturity, metadata);
        transaction.save();
    }
}