gqlgenメモ

-- +migrate Up
CREATE TABLE sale (
  id BIGINT PRIMARY KEY
  , created_at BIGINT NOT NULL DEFAULT 0
);

COMMENT ON TABLE sale IS '受注データ';
COMMENT ON COLUMN sale.created_at IS '作成日時(UNIXTIME)かつ受注日時';

CREATE TABLE detail (
  id BIGINT PRIMARY KEY
  , sale_id BIGINT  NOT NULL DEFAULT 0
  , name    TEXT    NOT NULL DEFAULT ''
  , price   INTEGER NOT NULL DEFAULT 0
  , FOREIGN KEY (sale_id) REFERENCES sale (id)
);

COMMENT ON TABLE  detail         IS '詳細データ';
COMMENT ON COLUMN detail.sale_id IS '親ID';
COMMENT ON COLUMN detail.name    IS '商品名';
COMMENT ON COLUMN detail.price   IS '価格';

-- +migrate Down
DROP TABLE sale;
DROP TABLE product;

xo pgsql://postgres@127.0.0.1:5432/hogedb?sslmode=disable -o ./model --template-path .xo_templates

type PageInfo {
  endCursor: Int # 現在ページの最終データのIDをもたせる
  hasNextPage: Boolean # 次のページがあるかどうか？
}

type Detail {
  id: Int!
  saleId: Int!
  name: String!
  price: Int!
  productId: Int!
}

type Sale {
  id: Int!
  createdAt: Int!
  details: [Detail!]!
}

type Sales {
  totalCount: Int! # 全部で何件あるのか？
  edges: [Sale!]!
  pageInfo: PageInfo
}

type Query {
  sales(
    first: Int
    after: Int
    start: Int
    finish: Int
    keyword: String
    orderBy: String
  ): Sales!
}

query {
  sales {
    edges {
      id
      details {
        id
        name
      }
    }
  }
}

go run scripts/gqlgen.go init

panic("not implemented")

go get github.com/vektah/dataloaden
dataloaden -keys int -slice github.com/miiton/hogehoge/model.Detail

package hogehoge

import (
	"context"
	"log"
	"net/http"
	"time"

	"github.com/jmoiron/sqlx"
	"github.com/miiton/hogehoge/model"
	"golang.org/x/xerrors"
)

type ctxKeyType struct{ name string }

var ctxKey = ctxKeyType{"detailLoader"}

func DataloaderMiddleware(db *sqlx.DB, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		wait := 250 * time.Microsecond

		// detail loader - 1:N
		detailLoader := DetailSliceLoader{
			maxBatch: 100,
			wait:     wait,
			fetch: func(keys []int) ([][]model.Detail, []error) {
				// NOTE: keysに最大maxBatch分の親IDが入る（今回の場合は sale_id ）
				// NOTE: wait入れてもどこでwait入るのかいまいちわからんかった

				// NOTE: [バッチ単位の[値のスライス]]を返す
				resultSet := make([][]model.Detail, len(keys))
				errors := make([]error, len(keys))
				var details []model.Detail

				// NOTE: keys分のデータ(= maxBatch = 最大100件)を取得する
				// NOTE: ここはsqlxの力で記述を省力化!!
				query, args, err := sqlx.In("SELECT * FROM detail WHERE sale_id IN (?);", keys)
				query = db.Rebind(query)
				if err != nil {
					log.Fatalf("%+v\n", xerrors.Errorf("detailLoader: ", err))
				}

				err = db.Select(&details, query, args...)
				if err != nil {
					log.Println(query)

					// NOTE: 1クエリで発生したエラーをkeys分複製して返すようにする
					for i, _ := range keys {
						errors[i] = err
					}
				}

				// NOTE: DBから取得したデータを各親項目に分配する
				// メモリ上でやるからはやいぜ
				for i, key := range keys {
					for _, detail := range details {
						if detail.SaleID == key {
							resultSet[i] = append(resultSet[i], detail)
						}
					}
				}

				return resultSet, errors
			},
		}
		ctx := context.WithValue(r.Context(), ctxKey, &detailLoader)
		r = r.WithContext(ctx)
		next.ServeHTTP(w, r)
	})
}

func ctxLoaders(ctx context.Context) *DetailSliceLoader {
	return ctx.Value(ctxKey).(*DetailSliceLoader)
}

package main

import (
	"log"
	"net/http"
	"os"

	"github.com/99designs/gqlgen/handler"
	"github.com/miiton/hogehoge"
	"golang.org/x/xerrors"
)

const defaultPort = "8080"

func main() {
	port := os.Getenv("PORT")
	if port == "" {
		port = defaultPort
	}

	http.Handle("/", handler.Playground("GraphQL playground", "/query"))
	queryHandler := handler.GraphQL(hogehoge.NewExecutableSchema(hogehoge.Config{Resolvers: &hogehoge.Resolver{}}))

	db, err := hogehoge.ConnectDB()
	if err != nil {
		err = xerrors.Errorf("server.go main():", err)
		log.Fatalf("%+v\n", err)
	}
	//                                 ↓ここ大事！
	http.Handle("/query", hogehoge.DataloaderMiddleware(db, queryHandler))

	log.Printf("connect to http://localhost:%s/ for GraphQL playground", port)
	log.Fatal(http.ListenAndServe(":"+port, nil))
}