I am currently working on implementing DataLoader with Mongoose for the following use case:
export const PurchaseOrderType = new GraphQLObjectType({
name: "PurchaseOrder",
description: "PurchaseOrder",
interfaces: () => [NodeInterface],
isTypeOf: value => value instanceof PurchaseOrderModel,
fields: () => ({
id: {
type: new GraphQLNonNull(GraphQLID),
resolve: obj => dbIdToNodeId(obj._id, "PurchaseOrder")
},
name: {
type: new GraphQLNonNull(GraphQLString)
},
customer: {
type: CustomerType,
resolve: (source, args, context) => {
return context.customerLoader.load(source.customer_id);
}
}
})
});
export default () => {
return graphqlHTTP((req, res, graphQLParams) => {
return {
schema: schema,
graphiql: true,
pretty: true,
context: {
customerLoader: customerGetByIdsLoader()
},
formatError: error => ({
message: error.message,
locations: error.locations,
stack: error.stack,
path: error.path
})
};
});
};
export const customerGetByIdsLoader = () =>
new DataLoader(ids => {
return customerGetByIds(ids);
});
export const customerGetByIds = async ids => {
let result = await Customer.find({ _id: { $in: ids }, deletedAt: null }).exec();
let rows = ids.map(id => {
let found = result.find(item => {
return item.id.equals(id);
});
return found ? found : null; << === found always undefined
});
return rows;
};
During the implementation, I encountered the following challenges while loading multiple PurchaseOrders:
One specific customer_id is being repetitively called in the ids parameter of the DataLoader. For instance, the id
5cee853eae92f6021f297f45is being requested across various loader calls, implying a possible cache malfunction.The variable 'found' remains false consistently when processing the read results, despite correctly comparing the ids.