forked from 99designs/gqlgen
/
dataloaders.go
119 lines (98 loc) · 3.32 KB
/
dataloaders.go
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//go:generate gorunpkg github.com/vektah/dataloaden -keys int github.com/99designs/gqlgen/example/dataloader.Address
//go:generate gorunpkg github.com/vektah/dataloaden -keys int -slice github.com/99designs/gqlgen/example/dataloader.Order
//go:generate gorunpkg github.com/vektah/dataloaden -keys int -slice github.com/99designs/gqlgen/example/dataloader.Item
package dataloader
import (
"context"
"fmt"
"math/rand"
"net/http"
"strconv"
"strings"
"time"
)
type ctxKeyType struct{ name string }
var ctxKey = ctxKeyType{"userCtx"}
type loaders struct {
addressByID *AddressLoader
ordersByCustomer *OrderSliceLoader
itemsByOrder *ItemSliceLoader
}
func LoaderMiddleware(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
ldrs := loaders{}
// set this to zero what happens without dataloading
wait := 250 * time.Microsecond
// simple 1:1 loader, fetch an address by its primary key
ldrs.addressByID = &AddressLoader{
wait: wait,
maxBatch: 100,
fetch: func(keys []int) ([]*Address, []error) {
var keySql []string
for _, key := range keys {
keySql = append(keySql, strconv.Itoa(key))
}
fmt.Printf("SELECT * FROM address WHERE id IN (%s)\n", strings.Join(keySql, ","))
time.Sleep(5 * time.Millisecond)
addresses := make([]*Address, len(keys))
errors := make([]error, len(keys))
for i, key := range keys {
addresses[i] = &Address{Street: "home street", Country: "hometon " + strconv.Itoa(key)}
}
return addresses, errors
},
}
// 1:M loader
ldrs.ordersByCustomer = &OrderSliceLoader{
wait: wait,
maxBatch: 100,
fetch: func(keys []int) ([][]Order, []error) {
var keySql []string
for _, key := range keys {
keySql = append(keySql, strconv.Itoa(key))
}
fmt.Printf("SELECT * FROM orders WHERE customer_id IN (%s)\n", strings.Join(keySql, ","))
time.Sleep(5 * time.Millisecond)
orders := make([][]Order, len(keys))
errors := make([]error, len(keys))
for i, key := range keys {
id := 10 + rand.Int()%3
orders[i] = []Order{
{ID: id, Amount: rand.Float64(), Date: time.Now().Add(-time.Duration(key) * time.Hour)},
{ID: id + 1, Amount: rand.Float64(), Date: time.Now().Add(-time.Duration(key) * time.Hour)},
}
// if you had another customer loader you would prime its cache here
// by calling `ldrs.ordersByID.Prime(id, orders[i])`
}
return orders, errors
},
}
// M:M loader
ldrs.itemsByOrder = &ItemSliceLoader{
wait: wait,
maxBatch: 100,
fetch: func(keys []int) ([][]Item, []error) {
var keySql []string
for _, key := range keys {
keySql = append(keySql, strconv.Itoa(key))
}
fmt.Printf("SELECT * FROM items JOIN item_order WHERE item_order.order_id IN (%s)\n", strings.Join(keySql, ","))
time.Sleep(5 * time.Millisecond)
items := make([][]Item, len(keys))
errors := make([]error, len(keys))
for i := range keys {
items[i] = []Item{
{Name: "item " + strconv.Itoa(rand.Int()%20+20)},
{Name: "item " + strconv.Itoa(rand.Int()%20+20)},
}
}
return items, errors
},
}
dlCtx := context.WithValue(r.Context(), ctxKey, ldrs)
next.ServeHTTP(w, r.WithContext(dlCtx))
})
}
func ctxLoaders(ctx context.Context) loaders {
return ctx.Value(ctxKey).(loaders)
}