以下是来自官方的一个user group pet 的查询demo
参考关系图
环境准备
- docker-compose mysql 环境
version: "3"
services:
mysql:
image: mysql:5.7.16
ports:
- 3306:3306
command: --character-set-server=utf8mb4 --collation-server=utf8mb4_unicode_ci
environment:
MYSQL_ROOT_PASSWORD: dalongrong
MYSQL_DATABASE: gogs
MYSQL_USER: gogs
MYSQL_PASSWORD: dalongrong
TZ: Asia/Shanghai
- golang mod 项目
go mod init github.com/rongfengliang/ent-pet-user-group
生成实体模型
- 生成schema
entc init Pet User Group
- 配置schema 字段以及边
pets
package schema
import (
"github.com/facebookincubator/ent"
"github.com/facebookincubator/ent/schema/edge"
"github.com/facebookincubator/ent/schema/field"
)
// Pet holds the schema definition for the Pet entity.
type Pet struct {
ent.Schema
}
// Fields of the Pet.
func (Pet) Fields() []ent.Field {
return []ent.Field{
field.String("name"),
}
}
// Edges of the Pet.
func (Pet) Edges() []ent.Edge {
return []ent.Edge{
edge.To("friends", Pet.Type),
edge.From("owner", User.Type).
Ref("pets").
Unique(),
}
}
user
package schema
import (
"github.com/facebookincubator/ent"
"github.com/facebookincubator/ent/schema/edge"
"github.com/facebookincubator/ent/schema/field"
)
// User holds the schema definition for the User entity.
type User struct {
ent.Schema
}
// Fields of the User.
func (User) Fields() []ent.Field {
return []ent.Field{
field.Int("age"),
field.String("name"),
}
}
// Edges of the User.
func (User) Edges() []ent.Edge {
return []ent.Edge{
edge.To("pets", Pet.Type),
edge.To("friends", User.Type),
edge.From("groups", Group.Type).
Ref("users"),
edge.From("manage", Group.Type).
Ref("admin"),
}
}
group
package schema
import (
"github.com/facebookincubator/ent"
"github.com/facebookincubator/ent/schema/edge"
"github.com/facebookincubator/ent/schema/field"
)
// Group holds the schema definition for the Group entity.
type Group struct {
ent.Schema
}
// Fields of the Group.
func (Group) Fields() []ent.Field {
return []ent.Field{
field.String("name"),
}
}
// Edges of the Group.
func (Group) Edges() []ent.Edge {
return []ent.Edge{
edge.To("users", User.Type),
edge.To("admin", User.Type).
Unique(),
}
}
生成边以及定点数据
package main
import (
"context"
"fmt"
"log"
_ "github.com/go-sql-driver/mysql"
"github.com/rongfengliang/ent-pet-user-group/ent"
)
func main() {
client, err := ent.Open("mysql", "root:dalongrong@tcp(127.0.0.1)/gogs")
if err != nil {
log.Fatalf("failed opening connection to sqlite: %v", err)
}
defer client.Close()
ctx := context.Background()
Gen(ctx, client.Debug())
}
// Gen for generate demo datas
func Gen(ctx context.Context, client *ent.Client) error {
hub, err := client.Group.
Create().
SetName("Github").
Save(ctx)
if err != nil {
return fmt.Errorf("failed creating the group: %v", err)
}
// Create the admin of the group.
// Unlike `Save`, `SaveX` panics if an error occurs.
dan := client.User.
Create().
SetAge(29).
SetName("Dan").
AddManage(hub).
SaveX(ctx)
// Create "Ariel" and its pets.
a8m := client.User.
Create().
SetAge(30).
SetName("Ariel").
AddGroups(hub).
AddFriends(dan).
SaveX(ctx)
pedro := client.Pet.
Create().
SetName("Pedro").
SetOwner(a8m).
SaveX(ctx)
xabi := client.Pet.
Create().
SetName("Xabi").
SetOwner(a8m).
SaveX(ctx)
// Create "Alex" and its pets.
alex := client.User.
Create().
SetAge(37).
SetName("Alex").
SaveX(ctx)
coco := client.Pet.
Create().
SetName("Coco").
SetOwner(alex).
AddFriends(pedro).
SaveX(ctx)
fmt.Println("Pets created:", pedro, xabi, coco)
// Output:
// Pets created: Pet(id=1, name=Pedro) Pet(id=2, name=Xabi) Pet(id=3, name=Coco)
return nil
}
一些查询
为了方便查看生成的sql 我使用了debug，同时也可以开启慢查询
set global slow_query_log=1;
set global long_query_time=0;
- 一个demo
上面的遍历从一个Group实体开始，继续到其admin（边），继续到其friends（边），获取其pets（边），获取每个宠物的
friends（边），并请求其所有者
参考图
代码：
func Traverse(ctx context.Context, client *ent.Client) error {
owner, err := client.Group. // GroupClient.
Query(). // Query builder.
Where(group.Name("Github")). // Filter only Github group (only 1).
QueryAdmin(). // Getting Dan.
QueryFriends(). // Getting Dan's friends: [Ariel].
QueryPets(). // Their pets: [Pedro, Xabi].
QueryFriends(). // Pedro's friends: [Coco], Xabi's friends: [].
QueryOwner(). // Coco's owner: Alex.
Only(ctx) // Expect only one entity to return in the query.
if err != nil {
return fmt.Errorf("failed querying the owner: %v", err)
}
fmt.Println(owner)
// Output:
// User(id=3, age=37, name=Alex)
return nil
}
效果：
2019/10/15 13:10:12 driver.Query: query=SELECT DISTINCT `users`.`id`, `users`.`age`, `users`.`name` FROM `users` JOIN (SELECT `pets`.`owner_id` FROM
`pets` JOIN (SELECT `pet_friends`.`friend_id` FROM `pet_friends` JOIN (SELECT `pets`.`id` FROM `pets` JOIN (SELECT `users`.`id` FROM `users` JOIN (
SELECT `user_friends`.`friend_id` FROM `user_friends` JOIN (SELECT `users`.`id` FROM `users` JOIN (SELECT `groups`.`admin_id` FROM `groups` WHERE `g
roups`.`name` = ?) AS `t1` ON `users`.`id` = `t1`.`admin_id`) AS `t1` ON `user_friends`.`user_id` = `t1`.`id`) AS `t1` ON `users`.`id` = `t1`.`frien
d_id`) AS `t1` ON `pets`.`owner_id` = `t1`.`id`) AS `t1` ON `pet_friends`.`pet_id` = `t1`.`id`) AS `t1` ON `pets`.`id` = `t1`.`friend_id`) AS `t1` O
N `users`.`id` = `t1`.`owner_id` LIMIT ? args=[Github 2]
User(id=3, age=37, name=Alex)
sql 查询计划
EXPLAIN SELECT
DISTINCT `users`.`id`,
`users`.`age`,
`users`.`name`
FROM
`users`
JOIN (
SELECT
`pets`.`owner_id`
FROM
`pets`
JOIN (
SELECT
`pet_friends`.`friend_id`
FROM
`pet_friends`
JOIN (
SELECT
`pets`.`id`
FROM
`pets`
JOIN (
SELECT
`users`.`id`
FROM
`users`
JOIN (
SELECT
`user_friends`.`friend_id`
FROM
`user_friends`
JOIN (
SELECT
`users`.`id`
FROM
`users`
JOIN (
SELECT
`groups`.`admin_id`
FROM
`groups`
WHERE
`groups`.`name` = 'Github'
) AS `t1` ON `users`.`id` = `t1`.`admin_id`
) AS `t1` ON `user_friends`.`user_id` = `t1`.`id`
) AS `t1` ON `users`.`id` = `t1`.`friend_id`
) AS `t1` ON `pets`.`owner_id` = `t1`.`id`
) AS `t1` ON `pet_friends`.`pet_id` = `t1`.`id`
) AS `t1` ON `pets`.`id` = `t1`.`friend_id`
) AS `t1` ON `users`.`id` = `t1`.`owner_id`
效果：
- 另外一个demo
我们要获取所有owner（edge）是friend 某个组admin（边）的宠物（实体）。
func Traverse(ctx context.Context, client *ent.Client) error {
pets, err := client.Pet.
Query().
Where(
pet.HasOwnerWith(
user.HasFriendsWith(
user.HasManage(),
),
),
).
All(ctx)
if err != nil {
return fmt.Errorf("failed querying the pets: %v", err)
}
fmt.Println(pets)
// Output:
// [Pet(id=1, name=Pedro) Pet(id=2, name=Xabi)]
return nil
}
效果
go run cmd/query2/main.go
2019/10/15 13:18:47 driver.Query: query=SELECT DISTINCT `pets`.`id`, `pets`.`name` FROM `pets` WHERE `pets`.`owner_id` IN (SELECT `id` FROM `users`
WHERE `users`.`id` IN (SELECT `user_friends`.`user_id` FROM `user_friends` JOIN `users` AS `t0` ON `user_friends`.`friend_id` = `t0`.`id` WHERE `t0`
.`id` IN (SELECT `admin_id` FROM `groups` WHERE `admin_id` IS NOT NULL))) args=[]
[Pet(id=1, name=Pedro) Pet(id=2, name=Xabi)]
查询计划
EXPLAIN SELECT
DISTINCT `pets`.`id`,
`pets`.`name`
FROM
`pets`
WHERE
`pets`.`owner_id` IN (
SELECT
`id`
FROM
`users`
WHERE
`users`.`id` IN (
SELECT
`user_friends`.`user_id`
FROM
`user_friends`
JOIN `users` AS `t0` ON `user_friends`.`friend_id` = `t0`.`id`
WHERE
`t0`.`id` IN (
SELECT
`admin_id`
FROM
`groups`
WHERE
`admin_id` IS NOT NULL
)
)
)
效果 
参考资料
https://entgo.io/docs/traversals/
https://github.com/rongfengliang/ent-pet-user-group