add batchDelegate package

Add key option within type merging config to enable batch loading for lists.

This minimal version of batching uses cached dataLoaders to create a separate batch for each list rather than for every similar query within the resolution tree.

This is because a new dataloader is created for every new info.fieldNodes object, which is memoized upstream by graphql-js within resolution of a given list to allow the loader to be used for items of that list.

A future version could provide an option to batch by similar target fieldName/selectionSet, but this version may hit the sweet spot in terms of code complexity and batching behavior.

see:
#1710

packages/batchDelegate/package.json

@@ -0,0 +1,34 @@
+{
+ "name": "@graphql-tools/batchDelegate",
+ "version": "6.0.12",
+ "description": "A set of utils for faster development of GraphQL tools",
+ "repository": "git@github.com:ardatan/graphql-tools.git",
+ "license": "MIT",
+ "sideEffects": false,
+ "main": "dist/index.cjs.js",
+ "module": "dist/index.esm.js",
+ "typings": "dist/index.d.ts",
+ "typescript": {
+ "definition": "dist/index.d.ts"
+ },
+ "peerDependencies": {
+ "graphql": "^14.0.0 || ^15.0.0"
+ },
+ "buildOptions": {
+ "input": "./src/index.ts"
+ },
+ "dependencies": {
+ "@graphql-tools/delegate": "6.0.12",
+ "dataloader": "2.0.0",
+ "tslib": "~2.0.0"
+ },
+ "devDependencies": {
+ "@graphql-tools/schema": "6.0.12",
+ "@graphql-tools/stitch": "6.0.12",
+ "@graphql-tools/utils": "6.0.12"
+ },
+ "publishConfig": {
+ "access": "public",
+ "directory": "dist"
+ }
+}

packages/batchDelegate/src/createBatchDelegateFn.ts

@@ -0,0 +1,51 @@
+import { FieldNode, getNamedType, GraphQLOutputType, GraphQLList } from 'graphql';
+
+import DataLoader from 'dataloader';
+
+import { delegateToSchema } from '@graphql-tools/delegate';
+
+import { BatchDelegateOptionsFn, BatchDelegateFn, BatchDelegateOptions } from './types';
+
+export function createBatchDelegateFn<K = any, V = any, C = K>(
+ argFn: (args: ReadonlyArray<K>) => Record<string, any>,
+ batchDelegateOptionsFn: BatchDelegateOptionsFn,
+ dataLoaderOptions?: DataLoader.Options<K, V, C>
+): BatchDelegateFn<K> {
+ let cache: WeakMap<ReadonlyArray<FieldNode>, DataLoader<K, V, C>>;
+
+ function createBatchFn(options: BatchDelegateOptions) {
+ return async (keys: ReadonlyArray<K>) => {
+ const results = await delegateToSchema({
+ returnType: new GraphQLList(getNamedType(options.info.returnType) as GraphQLOutputType),
+ args: argFn(keys),
+ ...batchDelegateOptionsFn(options),
+ });
+ return Array.isArray(results) ? results : keys.map(() => results);
+ };
+ }
+
+ function getLoader(options: BatchDelegateOptions) {
+ if (!cache) {
+ cache = new WeakMap();
+ const batchFn = createBatchFn(options);
+ const newValue = new DataLoader<K, V, C>(keys => batchFn(keys), dataLoaderOptions);
+ cache.set(options.info.fieldNodes, newValue);
+ return newValue;
+ }
+
+ const cachedValue = cache.get(options.info.fieldNodes);
+ if (cachedValue === undefined) {
+ const batchFn = createBatchFn(options);
+ const newValue = new DataLoader<K, V, C>(keys => batchFn(keys), dataLoaderOptions);
+ cache.set(options.info.fieldNodes, newValue);
+ return newValue;
+ }
+
+ return cachedValue;
+ }
+
+ return options => {
+ const loader = getLoader(options);
+ return loader.load(options.key);
+ };
+}

packages/batchDelegate/src/index.ts

@@ -0,0 +1,3 @@
+export { createBatchDelegateFn } from './createBatchDelegateFn';
+
+export * from './types';

packages/batchDelegate/src/types.ts

@@ -0,0 +1,14 @@
+import { IDelegateToSchemaOptions } from '@graphql-tools/delegate';
+
+export type BatchDelegateFn<TContext = Record<string, any>, K = any> = (
+ batchDelegateOptions: BatchDelegateOptions<TContext, K>
+) => any;
+
+export type BatchDelegateOptionsFn<TContext = Record<string, any>, K = any> = (
+ batchDelegateOptions: BatchDelegateOptions<TContext, K>
+) => IDelegateToSchemaOptions<TContext>;
+
+export interface BatchDelegateOptions<TContext = Record<string, any>, K = any>
+ extends Omit<IDelegateToSchemaOptions<TContext>, 'args'> {
+ key: K;
+}

packages/stitch/tests/typeMerging.example.test.ts → packages/batchDelegate/tests/typeMerging.example.test.ts

@@ -1,16 +1,16 @@
-// Conversion of Apollo Federation demo from https://github.com/apollographql/federation-demo.
-// See: https://github.com/ardatan/graphql-tools/issues/1697
+// Conversion of Apollo Federation demo
+// Compare: https://github.com/apollographql/federation-demo
+// See also:
+// https://github.com/ardatan/graphql-tools/issues/1697
+// https://github.com/ardatan/graphql-tools/issues/1710
 
 import { graphql } from 'graphql';
 
 import { makeExecutableSchema } from '@graphql-tools/schema';
-
 import { ExecutionResult } from '@graphql-tools/utils';
-
-import { stitchSchemas } from '../src/stitchSchemas';
+import { stitchSchemas } from '@graphql-tools/stitch';
 
 describe('merging using type merging', () => {
-
  const users = [
  {
  id: '1',
@@ -31,6 +31,7 @@ describe('merging using type merging', () => {
  type Query {
  me: User
  _userById(id: ID!): User
+ _usersById(ids: [ID!]!): [User]
  }
  type User {
  id: ID!
@@ -42,6 +43,7 @@ describe('merging using type merging', () => {
  Query: {
  me: () => users[0],
  _userById: (_root, { id }) => users.find(user => user.id === id),
+ _usersById: (_root, { ids }) => ids.map((id: any) => users.find(user => user.id === id)),
  },
  },
  });
@@ -111,6 +113,7 @@ describe('merging using type merging', () => {
  type Query {
  topProducts(first: Int = 5): [Product]
  _productByUpc(upc: String!): Product
+ _productsByUpc(upcs: [String!]!): [Product]
  }
  type Product {
  upc: String!
@@ -123,6 +126,7 @@ describe('merging using type merging', () => {
  Query: {
  topProducts: (_root, args) => products.slice(0, args.first),
  _productByUpc: (_root, { upc }) => products.find(product => product.upc === upc),
+ _productsByUpc: (_root, { upcs }) => upcs.map((upc: any) => products.find(product => product.upc === upc)),
  }
  },
  });
@@ -179,8 +183,10 @@ describe('merging using type merging', () => {
  }
  type Query {
  _userById(id: ID!): User
+ _usersById(ids: [ID!]!): [User]
  _reviewById(id: ID!): Review
  _productByUpc(upc: String!): Product
+ _productsByUpc(upcs: [String!]!): [Product]
  }
  `,
  resolvers: {
@@ -201,7 +207,9 @@ describe('merging using type merging', () => {
  Query: {
  _reviewById: (_root, { id }) => reviews.find(review => review.id === id),
  _userById: (_root, { id }) => ({ id }),
+ _usersById: (_root, { ids }) => ids.map((id: string) => ({ id })),
  _productByUpc: (_, { upc }) => ({ upc }),
+ _productsByUpc: (_, { upcs }) => upcs.map((upc: string) => ({ upc })),
  },
  }
  });
@@ -212,8 +220,8 @@ describe('merging using type merging', () => {
  schema: accountsSchema,
  merge: {
  User: {
- fieldName: '_userById',
  selectionSet: '{ id }',
+ fieldName: '_userById',
  args: ({ id }) => ({ id })
  }
  }
@@ -222,8 +230,8 @@ describe('merging using type merging', () => {
  schema: inventorySchema,
  merge: {
  Product: {
- fieldName: '_productByUpc',
  selectionSet: '{ upc weight price }',
+ fieldName: '_productByUpc',
  args: ({ upc, weight, price }) => ({ upc, weight, price }),
  }
  }
@@ -232,8 +240,8 @@ describe('merging using type merging', () => {
  schema: productsSchema,
  merge: {
  Product: {
- fieldName: '_productByUpc',
  selectionSet: '{ upc }',
+ fieldName: '_productByUpc',
  args: ({ upc }) => ({ upc }),
  }
  }
@@ -242,13 +250,14 @@ describe('merging using type merging', () => {
  schema: reviewsSchema,
  merge: {
  User: {
- fieldName: '_userById',
  selectionSet: '{ id }',
- args: ({ id }) => ({ id }),
+ fieldName: '_usersById',
+ args: (ids) => ({ ids }),
+ key: ({ id }) => id,
  },
  Product: {
- fieldName: '_productByUpc',
  selectionSet: '{ upc }',
+ fieldName: '_productByUpc',
  args: ({ upc }) => ({ upc }),
  },
  }

packages/delegate/src/types.ts

@@ -135,7 +135,8 @@ export interface SubschemaConfig {
 export interface MergedTypeConfig {
  selectionSet?: string;
  fieldName?: string;
- args?: (originalResult: any) => Record<string, any>;
+ args?: (source: any) => Record<string, any>;
+ key?: (originalResult: any) => any;
  resolve?: MergedTypeResolver;
 }
 

packages/stitch/src/stitchingInfo.ts

@@ -21,6 +21,7 @@ import {
 } from '@graphql-tools/utils';
 
 import { delegateToSchema, isSubschemaConfig, SubschemaConfig } from '@graphql-tools/delegate';
+import { createBatchDelegateFn } from '@graphql-tools/batchDelegate';
 
 import { MergeTypeCandidate, MergedTypeInfo, StitchingInfo, MergeTypeFilter } from './types';
 
@@ -103,18 +104,42 @@ function createMergedTypes(
  }
 
  if (!mergedTypeConfig.resolve) {
- mergedTypeConfig.resolve = (originalResult, context, info, subschema, selectionSet) =>
- delegateToSchema({
- schema: subschema,
- operation: 'query',
- fieldName: mergedTypeConfig.fieldName,
- returnType: getNamedType(info.returnType) as GraphQLOutputType,
- args: mergedTypeConfig.args(originalResult),
- selectionSet,
- context,
- info,
- skipTypeMerging: true,
- });
+ if (mergedTypeConfig.key != null) {
+ const batchDelegateToSubschema = createBatchDelegateFn(
+ mergedTypeConfig.args,
+ ({ schema, selectionSet, context, info }) => ({
+ schema,
+ operation: 'query',
+ fieldName: mergedTypeConfig.fieldName,
+ selectionSet,
+ context,
+ info,
+ skipTypeMerging: true,
+ })
+ );
+
+ mergedTypeConfig.resolve = (originalResult, context, info, subschema, selectionSet) =>
+ batchDelegateToSubschema({
+ key: mergedTypeConfig.key(originalResult),
+ schema: subschema,
+ context,
+ info,
+ selectionSet,
+ });
+ } else {
+ mergedTypeConfig.resolve = (originalResult, context, info, subschema, selectionSet) =>
+ delegateToSchema({
+ schema: subschema,
+ operation: 'query',
+ fieldName: mergedTypeConfig.fieldName,
+ returnType: getNamedType(info.returnType) as GraphQLOutputType,
+ args: mergedTypeConfig.args(originalResult),
+ selectionSet,
+ context,
+ info,
+ skipTypeMerging: true,
+ });
+ }
  }
 
  subschemas.push(subschemaConfig);