问题
I am attempting to use the DataLoader feature within the graphql-java-kickstart library:
https://github.com/graphql-java-kickstart
My application is a Spring Boot application using 2.3.0.RELEASE. And I using version 7.0.1 of the graphql-spring-boot-starter library.
The library is pretty easy to use and it works when I don't use the data loader. However, I am plagued by the N+1 SQL problem and as a result need to use the data loader to help alleviate this issue. When I execute a request, I end up getting this:
Can't resolve value (/findAccountById[0]/customers) : type mismatch error, expected type LIST got class com.daluga.api.account.domain.Customer
I am sure I am missing something in the configuration but really don't know what that is.
Here is my graphql schema:
type Account {
id: ID!
accountNumber: String!
customers: [Customer]
}
type Customer {
id: ID!
fullName: String
}
I have created a CustomGraphQLContextBuilder:
@Component
public class CustomGraphQLContextBuilder implements GraphQLServletContextBuilder {
private final CustomerRepository customerRepository;
public CustomGraphQLContextBuilder(CustomerRepository customerRepository) {
this.customerRepository = customerRepository;
}
@Override
public GraphQLContext build(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) {
return DefaultGraphQLServletContext.createServletContext(buildDataLoaderRegistry(), null).with(httpServletRequest).with(httpServletResponse).build();
}
@Override
public GraphQLContext build(Session session, HandshakeRequest handshakeRequest) {
return DefaultGraphQLWebSocketContext.createWebSocketContext(buildDataLoaderRegistry(), null).with(session).with(handshakeRequest).build();
}
@Override
public GraphQLContext build() {
return new DefaultGraphQLContext(buildDataLoaderRegistry(), null);
}
private DataLoaderRegistry buildDataLoaderRegistry() {
DataLoaderRegistry dataLoaderRegistry = new DataLoaderRegistry();
dataLoaderRegistry.register("customerDataLoader",
new DataLoader<Long, Customer>(accountIds ->
CompletableFuture.supplyAsync(() ->
customerRepository.findCustomersByAccountIds(accountIds), new SyncTaskExecutor())));
return dataLoaderRegistry;
}
}
I also have create an AccountResolver:
public CompletableFuture<List<Customer>> customers(Account account, DataFetchingEnvironment dfe) {
final DataLoader<Long, List<Customer>> dataloader = ((GraphQLContext) dfe.getContext())
.getDataLoaderRegistry().get()
.getDataLoader("customerDataLoader");
return dataloader.load(account.getId());
}
And here is the Customer Repository:
public List<Customer> findCustomersByAccountIds(List<Long> accountIds) {
Instant begin = Instant.now();
MapSqlParameterSource namedParameters = new MapSqlParameterSource();
String inClause = getInClauseParamFromList(accountIds, namedParameters);
String sql = StringUtils.replace(SQL_FIND_CUSTOMERS_BY_ACCOUNT_IDS,"__ACCOUNT_IDS__", inClause);
List<Customer> customers = jdbcTemplate.query(sql, namedParameters, new CustomerRowMapper());
Instant end = Instant.now();
LOGGER.info("Total Time in Millis to Execute findCustomersByAccountIds: " + Duration.between(begin, end).toMillis());
return customers;
}
I can put a break point in the Customer Repository and see the SQL execute and it returns a List of Customer objects. You can also see that the schema wants an array of customers. If I remove the code above and put in the resolver to get the customers one by one....it works....but is really slow.
What am I missing in the configuration that would cause this?
Can't resolve value (/findAccountById[0]/customers) : type mismatch error, expected type LIST got class com.daluga.api.account.domain.Customer
Thanks for your help!
Dan
回答1:
In the CustomGraphQLContextBuilder
,
I think you should have registered the DataLoader as :
...
dataLoaderRegistry.register("customerDataLoader",
new DataLoader<Long, List<Customer>>(accountIds ->
...
because, you are expecting a list of Customers
for one account Id.
That should work I guess.
回答2:
Thanks, @Bms bharadwaj! The issue was on my side in understanding how the data is returned in the dataloader. I ended up using a MappedBatchLoader to bring the data in a map. The key in the map being the accountId.
private DataLoader<Long, List<Customer>> getCustomerDataLoader() {
MappedBatchLoader<Long, List<Customer>> customerMappedBatchLoader = accountIds -> CompletableFuture.supplyAsync(() -> {
List<Customer> customers = customerRepository.findCustomersByAccountId(accountIds);
Map<Long, List<Customer>> groupByAccountId = customers.stream().collect(Collectors.groupingBy(cust -> cust.getAccountId()));
return groupByAaccountId;
});
// }, new SyncTaskExecutor());
return DataLoader.newMappedDataLoader(customerMappedBatchLoader);
}
This seems to have done the trick because before I was issuing hundreds of SQL statement and now down to 2 (one for the driver SQL...accounts and one for the customers).
来源:https://stackoverflow.com/questions/62093189/graphql-and-data-loader-using-the-graphql-java-kickstart-library