前几天看到消息Facebook孵化的ORM ent转为正式项目，出去好奇，简单体验了一下，使用上自己感觉比GORM好用，于是打算把官方的文档进行整理，也算是学习一下如何使用。
安装
ent orm 需要使用entc命令进行自动代码生成，所以需要先安装entc:
go get github.com/facebook/ent/cmd/entc
关于这个系列的所有代码笔记都会放到
github.com/peanut-cc/ent_orm_notes
快速使用
创建schema
正常情况下应该是在自己的项目根目录执行下面的命令，我这里是因为后续会有多个例子，为了让每个例子的内容独立，所以这里会在子目录下执行该命令
entc init User
这个命令执行后生成如下目录结构：
└── quick_user_example
└── ent
├── generate.go
└── schema
└── user.go
而schema目录下的user.go的内容也非常简单：
package schema
import "github.com/facebook/ent"
// User holds the schema definition for the User entity.
type User struct {
ent.Schema
}
// Fields of the User.
func (User) Fields() []ent.Field {
return nil
}
// Edges of the User.
func (User) Edges() []ent.Edge {
return nil
}
给schema添加字段
给schema添加字段非常简单，只需要在生成ent/schema/user.go的Fields方法中添加即可，修改之后的代码如下：
package schema
import (
"github.com/facebook/ent"
"github.com/facebook/ent/schema/field"
)
// User holds the schema definition for the User entity.
type User struct {
ent.Schema
}
// Fields of the User.
// 用于给 user 表定义字段
func (User) Fields() []ent.Field {
return []ent.Field{
field.Int("age").
Positive(),
field.String("name").Default("unknown"),
}
}
// Edges of the User.
func (User) Edges() []ent.Edge {
return nil
}
执行go generate ./ent 自动生成代码，执行命令后的目录结构为：
└── quick_user_example
└── ent
├── client.go
├── config.go
├── context.go
├── ent.go
├── enttest
│ └── enttest.go
├── generate.go
├── hook
│ └── hook.go
├── migrate
│ ├── migrate.go
│ └── schema.go
├── mutation.go
├── predicate
│ └── predicate.go
├── privacy
│ └── privacy.go
├── runtime
│ └── runtime.go
├── runtime.go
├── schema
│ └── user.go
├── tx.go
├── user
│ ├── user.go
│ └── where.go
├── user_create.go
├── user_delete.go
├── user.go
├── user_query.go
└── user_update.go
创建表到数据库
创建表并进行简单的添加数据，和查询数据：
package main
import (
"context"
"fmt"
"log"
_ "github.com/go-sql-driver/mysql"
"github.com/peanut-pg/ent_orm_notes/quick_user_example/ent"
"github.com/peanut-pg/ent_orm_notes/quick_user_example/ent/user"
)
func main() {
client, err := ent.Open("mysql", "root:123456@tcp(192.168.1.104:3306)/ent_orm?parseTime=True")
if err != nil {
log.Fatal(err)
}
defer client.Close()
ctx := context.Background()
// run the auto migration tool
if err := client.Schema.Create(ctx); err != nil {
log.Fatalf("failed creating schema resources:%v", err)
}
CreateUser(ctx, client)
peanut, err := QueryUser(ctx, client)
if err != nil {
log.Fatalln(err)
}
log.Fatalf("query user name is:%v, aget is %v", peanut.Name, peanut.Age)
}
// CreateUser 创建用户 name=peanut, age=18
func CreateUser(ctx context.Context, client *ent.Client) (*ent.User, error) {
u, err := client.User.
Create().
SetAge(18).
SetName("peanut").
Save(ctx)
if err != nil {
return nil, fmt.Errorf("failed creating user: %v", err)
}
log.Println("user was created: ", u)
return u, nil
}
// QueryUser 查询用户 where name=peanut
func QueryUser(ctx context.Context, client *ent.Client) (*ent.User, error) {
u, err := client.User.
Query().
Where(user.NameEQ("peanut")).
// `Only` fails if no user found,
// or more than 1 user returned.
Only(ctx)
if err != nil {
return nil, fmt.Errorf("failed querying user: %v", err)
}
log.Println("user returned: ", u)
return u, nil
}
创建表关系
还是用同样的方法创建Car和Group 的schema
entc init Car Group
分别给ent/schema目录下的car.go和group.go添加对应的字段信息
car.go文件：
package schema
import (
"github.com/facebook/ent"
"github.com/facebook/ent/schema/field"
)
// Car holds the schema definition for the Car entity.
type Car struct {
ent.Schema
}
// Fields of the Car.
func (Car) Fields() []ent.Field {
return []ent.Field{
field.String("model"),
field.Time("registered_at"),
}
}
// Edges of the Car.
func (Car) Edges() []ent.Edge {
return nil
}
group.go文件：
package schema
import (
"regexp"
"github.com/facebook/ent"
"github.com/facebook/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").
// regexp validation for group name.
Match(regexp.MustCompile("[a-zA-Z_]+$")),
}
}
// Edges of the Group.
func (Group) Edges() []ent.Edge {
return nil
}
在ent orm 中给表之间建立关系是通过Edges方法实现的，我们更改ent/schema/user.go中的Edges方法：
package schema
import (
"github.com/facebook/ent"
"github.com/facebook/ent/schema/edge"
"github.com/facebook/ent/schema/field"
)
// User holds the schema definition for the User entity.
type User struct {
ent.Schema
}
// Fields of the User.
// 用于给 user 表定义字段
func (User) Fields() []ent.Field {
return []ent.Field{
field.Int("age").
Positive(),
field.String("name").Default("unknown"),
}
}
// Edges of the User.
// 和Cars表建立关系
func (User) Edges() []ent.Edge {
return []ent.Edge{
edge.To("cars", Car.Type),
}
}
执行go generate ./ent 自动生成代码,然后重新生成一下表结构
然后在数据中执行show create table ent_orm.cars 查看表的详细结构语句：
CREATE TABLE `cars` (
`id` bigint(20) NOT NULL AUTO_INCREMENT,
`model` varchar(255) COLLATE utf8mb4_bin NOT NULL,
`registered_at` timestamp NULL DEFAULT NULL,
`user_cars` bigint(20) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `cars_users_cars` (`user_cars`),
CONSTRAINT `cars_users_cars` FOREIGN KEY (`user_cars`) REFERENCES `users` (`id`) ON DELETE SET NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
可以看出，通过在印记功能建立的外键关系
外键的数据添加
// CreateCars 创建 Tesla 和Ford 汽车，加该汽车属于user: peanut_pg
func CreateCars(ctx context.Context, client *ent.Client) (*ent.User, error) {
// creating new car with model "Tesla".
tesla, err := client.Car.
Create().
SetModel("Tesla").
SetRegisteredAt(time.Now()).
Save(ctx)
if err != nil {
return nil, fmt.Errorf("failed creating car: %v", err)
}
// creating new car with model "Ford".
ford, err := client.Car.
Create().
SetModel("Ford").
SetRegisteredAt(time.Now()).
Save(ctx)
if err != nil {
return nil, fmt.Errorf("failed creating car: %v", err)
}
log.Println("car was created: ", ford)
// create a new user, and add it the 2 cars.
peanut_pg, err := client.User.
Create().
SetAge(18).
SetName("peanut_pg").
// AddCars 将车属于user peanut_pg
AddCars(tesla, ford).
Save(ctx)
if err != nil {
return nil, fmt.Errorf("failed creating user: %v", err)
}
log.Println("user was created: ", peanut_pg)
return peanut_pg, nil
}
外键的查询
代码内容如下：
package main
import (
"context"
"fmt"
"log"
"time"
_ "github.com/go-sql-driver/mysql"
"github.com/peanut-pg/ent_orm_notes/quick_user_example/ent"
"github.com/peanut-pg/ent_orm_notes/quick_user_example/ent/car"
"github.com/peanut-pg/ent_orm_notes/quick_user_example/ent/user"
)
func main() {
client, err := ent.Open("mysql", "root:123456@tcp(192.168.1.104:3306)/ent_orm?parseTime=True")
if err != nil {
log.Fatal(err)
}
defer client.Close()
ctx := context.Background()
// run the auto migration tool
if err := client.Schema.Create(ctx); err != nil {
log.Fatalf("failed creating schema resources:%v", err)
}
peanut_pg, err := QueryUserByName(ctx, client, "peanut_pg")
if err != nil {
log.Fatalln(err)
}
QueryCars(ctx, peanut_pg)
}
// QueryUserByName 通过name 查询
func QueryUserByName(ctx context.Context, client *ent.Client, name string) (*ent.User, error) {
u, err := client.User.
Query().
Where(user.NameEQ(name)).
// `Only` fails if no user found,
// or more than 1 user returned.
Only(ctx)
if err != nil {
return nil, fmt.Errorf("failed querying user: %v", err)
}
log.Println("user returned: ", u)
return u, nil
}
// QueryCars 查询用户peanut_pg是否有Ford 这个车
func QueryCars(ctx context.Context, peanut_pg *ent.User) error {
cars, err := peanut_pg.QueryCars().All(ctx)
if err != nil {
return fmt.Errorf("failed querying user cars: %v", err)
}
log.Println("returned cars:", cars)
// what about filtering specific cars.
ford, err := peanut_pg.QueryCars().
Where(car.ModelEQ("Ford")).
Only(ctx)
if err != nil {
return fmt.Errorf("failed querying user cars: %v", err)
}
log.Println(ford)
return nil
}
反向查询
在平常的查询中我们还会经常用到一些反向查询，如我们想要查询这个车所属的用户是谁，这个时候需要修改
ent/schema/car.go 中的Edges方法：
package schema
import (
"github.com/facebook/ent"
"github.com/facebook/ent/schema/edge"
"github.com/facebook/ent/schema/field"
)
// Car holds the schema definition for the Car entity.
type Car struct {
ent.Schema
}
// Fields of the Car.
func (Car) Fields() []ent.Field {
return []ent.Field{
field.String("model"),
field.Time("registered_at"),
}
}
// Edges of the Car.
func (Car) Edges() []ent.Edge {
return []ent.Edge{
edge.From("owner", User.Type).
// create an inverse-edge called "owner" of type `User`
// and reference it to the "cars" edge (in User schema)
// explicitly using the `Ref` method.
Ref("cars").
// setting the edge to unique, ensure
// that a car can have only one owner.
Unique(),
}
}
先通过QueryCarByModel 查询一个Model=Tesla的汽车，然后通过QueryCarUser查看这个汽车的所属者是谁
// QueryCarByModel 查询car.model=Tesla
func QueryCarByModel(ctx context.Context, client *ent.Client) (*ent.Car, error) {
car, err := client.Car.Query().
Where(car.ModelEQ("Tesla")).
Only(ctx)
if err != nil {
return nil, fmt.Errorf("failed query car")
}
return car, nil
}
// QueryCarUser 查询car.model=Tesla的所属者是谁
func QueryCarUser(ctx context.Context, car *ent.Car) error {
owner, err := car.QueryOwner().Only(ctx)
if err != nil {
return fmt.Errorf("failed querying car %q owner:%v", car.Model, err)
}
log.Printf("car %q owner: %q\n", car.Model, owner.Name)
return nil
}
复杂查询
在上面的关系上再添加一个用户和组的关系，分别修改ent/schema/user.go和ent/schema/car.go 的Edges方法
// Edges of the User.
// 和Cars表建立关系
func (User) Edges() []ent.Edge {
return []ent.Edge{
edge.To("cars", Car.Type),
// create an inverse-edge called "groups" of type `Group`
// and reference it to the "users" edge (in Group schema)
// explicitly using the `Ref` method.
edge.From("groups", Group.Type).
Ref("users"),
}
}
// Edges of the Car.
func (Car) Edges() []ent.Edge {
return []ent.Edge{
edge.From("owner", User.Type).
// create an inverse-edge called "owner" of type `User`
// and reference it to the "cars" edge (in User schema)
// explicitly using the `Ref` method.
Ref("cars").
// setting the edge to unique, ensure
// that a car can have only one owner.
Unique(),
}
}
执行go generate ./ent 自动生成代码
通过如下方法生成基础数据：
// CreateGraph 创建基础数据
func CreateGraph(ctx context.Context, client *ent.Client) error {
// first, create the users.
a8m, err := client.User.
Create().
SetAge(30).
SetName("Ariel").
Save(ctx)
if err != nil {
return err
}
neta, err := client.User.
Create().
SetAge(28).
SetName("Neta").
Save(ctx)
if err != nil {
return err
}
// then, create the cars, and attach them to the users in the creation.
_, err = client.Car.
Create().
SetModel("TeslaY").
SetRegisteredAt(time.Now()). // ignore the time in the graph.
SetOwner(a8m). // attach this graph to Ariel.
Save(ctx)
if err != nil {
return err
}
_, err = client.Car.
Create().
SetModel("TeslaX").
SetRegisteredAt(time.Now()). // ignore the time in the graph.
SetOwner(a8m). // attach this graph to Ariel.
Save(ctx)
if err != nil {
return err
}
_, err = client.Car.
Create().
SetModel("TeslaS").
SetRegisteredAt(time.Now()). // ignore the time in the graph.
SetOwner(neta). // attach this graph to Neta.
Save(ctx)
if err != nil {
return err
}
// create the groups, and add their users in the creation.
_, err = client.Group.
Create().
SetName("GitLab").
AddUsers(neta, a8m).
Save(ctx)
if err != nil {
return err
}
_, err = client.Group.
Create().
SetName("GitHub").
AddUsers(a8m).
Save(ctx)
if err != nil {
return err
}
log.Println("The graph was created successfully")
return nil
}
「三种查询例子」
// QueryGithub 查询group = GitHub 的用户的所有的汽车
func QueryGithub(ctx context.Context, client *ent.Client) error {
cars, err := client.Group.
Query().
Where(group.Name("GitHub")).
QueryUsers().
QueryCars().
All(ctx)
if err != nil {
return fmt.Errorf("failed getting cars:%v", err)
}
// cars returned: [Car(id=3, model=TeslaY, registered_at=Tue Aug 25 00:43:55 2020) Car(id=4, model=TeslaX, registered_at=Tue Aug 25 00:43:55 2020)]
log.Println("cars returned:", cars)
return nil
}
func QueryArielCars(ctx context.Context, client *ent.Client) error {
// Get "Ariel" from previous steps.
a8m := client.User.
Query().
Where(
user.HasCars(),
user.Name("Ariel"),
).
OnlyX(ctx)
cars, err := a8m. // Get the groups, that a8m is connected to:
QueryGroups(). // (Group(Name=GitHub), Group(Name=GitLab),)
QueryUsers(). // (User(Name=Ariel, Age=30), User(Name=Neta, Age=28),)
QueryCars(). //
Where( //
car.Not( // Get Neta and Ariel cars, but filter out
car.ModelEQ("TeslaX"), // those who named "Mazda"
),
).
All(ctx)
if err != nil {
return fmt.Errorf("failed getting cars: %v", err)
}
log.Println("cars returned:", cars)
// Output: (Car(Model=Tesla, RegisteredAt=<Time>), Car(Model=Ford, RegisteredAt=<Time>),)
return nil
}
// QueryGroupWithUsers 查询所有由用户的组
func QueryGroupWithUsers(ctx context.Context, client *ent.Client) error {
groups, err := client.Group.
Query().
Where(group.HasUsers()).
All(ctx)
if err != nil {
return fmt.Errorf("failed getting groups: %v", err)
}
log.Println("groups returned:", groups)
// Output: (Group(Name=GitHub), Group(Name=GitLab),)
return nil
}
延伸阅读
https://entgo.io/docs/getting-started/
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