ent orm筆記1---快速嚐鮮
阿新 • • 發佈：2020-08-26
前幾天看到訊息Facebook孵化的ORM ent轉為正式專案，出去好奇，簡單體驗了一下，使用上自己感覺比GORM好用，於是打算把官方的文件進行整理，也算是學習一下如何使用。
## 安裝
ent orm 需要使用entc命令進行自動程式碼生成，所以需要先安裝entc:
`go get github.com/facebook/ent/cmd/entc`
關於這個系列的所有程式碼筆記都會放到
`github.com/peanut-cc/ent_orm_notes`
## 快速使用
### 建立schema
正常情況下應該是在自己的專案根目錄執行下面的命令，我這裡是因為後續會有多個例子，為了讓每個例子的內容獨立，所以這裡會在子目錄下執行該命令
`entc init User`
這個命令執行後生成如下目錄結構：
```shell
└── quick_user_example
└── ent
├── generate.go
└── schema
└── user.go
```
而schema目錄下的user.go的內容也非常簡單：
```go
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
}
```
### 給schema新增欄位
給schema新增欄位非常簡單，只需要在生成`ent/schema/user.go`的`Fields`方法中新增即可，修改之後的程式碼如下：
```go
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.
// 用於給 user 表定義欄位
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
}
```
執行`go generate ./ent` 自動生成程式碼，執行命令後的目錄結構為：
```shell
└── 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
```
### 建立表到資料庫
建立表並進行簡單的新增資料，和查詢資料：
```go
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 建立使用者 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 查詢使用者 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
}
```
### 建立表關係
還是用同樣的方法建立Car和Group 的schema
`entc init Car Group`
分別給`ent/schema`目錄下的`car.go`和`group.go`新增對應的欄位資訊
`car.go`檔案：
```go
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`檔案：
```go
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 中給表之間建立關係是通過Edges方法實現的，我們更改`ent/schema/user.go`中的Edges方法：
```go
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.
// 用於給 user 表定義欄位
func (User) Fields() []ent.Field {
return []ent.Field{
field.Int("age").
Positive(),
field.String("name").Default("unknown"),
}
}
// Edges of the User.
// 和Cars表建立關係
func (User) Edges() []ent.Edge {
return []ent.Edge{
edge.To("cars", Car.Type),
}
}
```
執行`go generate ./ent` 自動生成程式碼,然後重新生成一下表結構
然後在資料中執行`show create table ent_orm.cars` 查看錶的詳細結構語句：
```sql
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，通過在印記功能建立的外來鍵關係
### 外來鍵的資料新增
```go
// CreateCars 建立 Tesla 和Ford 汽車，加該汽車屬於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 將車屬於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
}
```
### 外來鍵的查詢
程式碼內容如下：
```go
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 通過name 查詢
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 查詢使用者peanut_pg是否有Ford 這個車
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
}
```
### 反向查詢
在平常的查詢中我們還會經常用到一些反向查詢，如我們想要查詢這個車所屬的使用者是誰，這個時候需要修改
`ent/schema/car.go` 中的Edges方法：
```go
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(),
}
}
```
先通過`QueryCarByModel` 查詢一個Model=Tesla的汽車，然後通過`QueryCarUser `檢視這個汽車的所屬者是誰
```
// QueryCarByModel 查詢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 查詢car.model=Tesla的所屬者是誰
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
}
```
### 複雜查詢
在上面的關係上再新增一個使用者和組的關係，分別修改`ent/schema/user.go`和`ent/schema/car.go` 的Edges方法
```go
// Edges of the User.
// 和Cars表建立關係
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"),
}
}
```
```go
// 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(),
}
}
```
執行`go generate ./ent` 自動生成程式碼
通過如下方法生成基礎資料：
```go
// CreateGraph 建立基礎資料
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
}
```
**三種查詢例子**
```go
// QueryGithub 查詢group = GitHub 的使用者的所有的汽車
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
}
```
```go
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=