在前面幾篇文章中,我們經常使用的可能就是entc這個命令了,entc這個工具給帶來了很多功能,這篇文章主要整理關於ent orm 中Code Generation
之前的例子中有個知識點少整理了,就是關於如果我們想要看orm在執行過程中詳細原生sql語句是可以開啟Debug看到的,程式碼如下:
client, err := ent.Open("mysql", "root:123456@tcp(10.211.55.3:3306)/graph_traversal?parseTime=True",ent.Debug())
序言
Initialize A New Schema
通過類似如下命令可以生成Schema 模板:
entc init User Pet
init 將在ent/schema 目錄下建立兩個schema user.go 和 pet.go ,如果ent目錄不存在,則會建立
Generate Assets
在新增了fields 和 edges 後,可以在專案的根目錄執行entc generate 或者使用go generate 生成程式碼
go generate ./ent
Generate 命令生成以下內容:
- 用於與graph 互動的Client 和Tx物件
- schema 的CRUD生成器
- 每個schema型別的Entity物件
- 用於與構建互動的常量和斷言
- SQL方言的migrate 包
Version Compatibility Between entc
And ent
這裡主要是關於在專案中使用ent 的時候ent的版本要和entc的包的版本相同,並且專案中使用Go modules 進行包管理
Code Generation Options
要了解更多關於 codegen 選項的資訊,entc generate -h :
generate go code for the schema directory
Usage:
entc generate [flags] path
Examples:
entc generate ./ent/schema
entc generate github.com/a8m/x
Flags:
--header string override codegen header
-h, --help help for generate
--idtype [int int64 uint uint64 string] type of the id field (default int)
--storage string storage driver to support in codegen (default "sql")
--target string target directory for codegen
--template strings external templates to execute
Storage
entc 可以為 SQL 和 Gremlin 方言生成資產。
External Templates
接受要執行的外部 Go 模板。如果模板名稱已經由 entc 定義,它將覆蓋現有的名稱。否則,它將把執行輸出寫入與模板同名的檔案。Flag 格式支援如下檔案、目錄和 glob:
entc generate --template <dir-path> --template glob="path/to/*.tmpl" ./ent/schema
更多的資訊和例子可以在外部模板文件中找到
Use entc
As A Package
執行 entc 的另一個選項是將其作為一個包使用,如下所示:
package main
import (
"log"
"github.com/facebook/ent/entc"
"github.com/facebook/ent/entc/gen"
"github.com/facebook/ent/schema/field"
)
func main() {
err := entc.Generate("./schema", &gen.Config{
Header: "// Your Custom Header",
IDType: &field.TypeInfo{Type: field.TypeInt},
})
if err != nil {
log.Fatal("running ent codegen:", err)
}
}
Schema Description
如果想要得到我們定義的schema的描述資訊,可以通過如下命令:
entc describe ./ent/schema
以之前的例子中執行效果如下:
User:
+-------+--------+--------+----------+----------+---------+---------------+-----------+-----------------------+------------+
| Field | Type | Unique | Optional | Nillable | Default | UpdateDefault | Immutable | StructTag | Validators |
+-------+--------+--------+----------+----------+---------+---------------+-----------+-----------------------+------------+
| id | <nil> | false | false | false | false | false | false | json:"id,omitempty" | 0 |
| name | string | false | false | false | false | false | false | json:"name,omitempty" | 0 |
+-------+--------+--------+----------+----------+---------+---------------+-----------+-----------------------+------------+
+-----------+------+---------+-----------+----------+--------+----------+
| Edge | Type | Inverse | BackRef | Relation | Unique | Optional |
+-----------+------+---------+-----------+----------+--------+----------+
| followers | User | true | following | M2M | false | true |
| following | User | false | | M2M | false | true |
+-----------+------+---------+-----------+----------+--------+----------+
CRUD API
Create A New Client
MySQL
package main
import (
"log"
"<project>/ent"
_ "github.com/go-sql-driver/mysql"
)
func main() {
client, err := ent.Open("mysql", "<user>:<pass>@tcp(<host>:<port>)/<database>?parseTime=True")
if err != nil {
log.Fatal(err)
}
defer client.Close()
}
PostgreSQL
package main
import (
"log"
"<project>/ent"
_ "github.com/lib/pq"
)
func main() {
client, err := ent.Open("postgres","host=<host> port=<port> user=<user> dbname=<database> password=<pass>")
if err != nil {
log.Fatal(err)
}
defer client.Close()
}
SQLite
package main
import (
"log"
"<project>/ent"
_ "github.com/mattn/go-sqlite3"
)
func main() {
client, err := ent.Open("sqlite3", "file:ent?mode=memory&cache=shared&_fk=1")
if err != nil {
log.Fatal(err)
}
defer client.Close()
}
Gremlin (AWS Neptune)
package main
import (
"log"
"<project>/ent"
)
func main() {
client, err := ent.Open("gremlin", "http://localhost:8182")
if err != nil {
log.Fatal(err)
}
}
Create An Entity
Save a user.
a8m, err := client.User. // UserClient.
Create(). // User create builder.
SetName("a8m"). // Set field value.
SetNillableAge(age). // Avoid nil checks.
AddGroups(g1, g2). // Add many edges.
SetSpouse(nati). // Set unique edge.
Save(ctx) // Create and return.
SaveX a pet; Unlike Save, SaveX panics if an error occurs.
pedro := client.Pet. // PetClient.
Create(). // Pet create builder.
SetName("pedro"). // Set field value.
SetOwner(a8m). // Set owner (unique edge).
SaveX(ctx) // Create and return.
Create Many
Save a bulk of pets
names := []string{"pedro", "xabi", "layla"}
bulk := make([]*ent.PetCreate, len(names))
for i, name := range names {
bulk[i] = client.Pet.Create().SetName(name).SetOwner(a8m)
}
pets, err := client.Pet.CreateBulk(bulk...).Save(ctx)
Update One
更新一個從資料庫返回的entity
a8m, err = a8m.Update(). // User update builder.
RemoveGroup(g2). // Remove specific edge.
ClearCard(). // Clear unique edge.
SetAge(30). // Set field value
Save(ctx) // Save and return.
Update By ID
pedro, err := client.Pet. // PetClient.
UpdateOneID(id). // Pet update builder.
SetName("pedro"). // Set field name.
SetOwnerID(owner). // Set unique edge, using id.
Save(ctx) // Save and return.
Update Many
以斷言進行過濾
n, err := client.User. // UserClient.
Update(). // Pet update builder.
Where( //
user.Or( // (age >= 30 OR name = "bar")
user.AgeEQ(30), //
user.Name("bar"), // AND
), //
user.HasFollowers(), // UserHasFollowers()
). //
SetName("foo"). // Set field name.
Save(ctx) // exec and return.
通過edge 斷言進行查詢
n, err := client.User. // UserClient.
Update(). // Pet update builder.
Where( //
user.HasFriendsWith( // UserHasFriendsWith (
user.Or( // age = 20
user.Age(20), // OR
user.Age(30), // age = 30
) // )
), //
). //
SetName("a8m"). // Set field name.
Save(ctx) // exec and return.
Query The Graph
獲取所有使用者的關注者
users, err := client.User. // UserClient.
Query(). // User query builder.
Where(user.HasFollowers()). // filter only users with followers.
All(ctx) // query and return.
獲取特定使用者的所有跟隨者; 從graph中的一個節點開始遍歷
users, err := a8m.
QueryFollowers().
All(ctx)
獲取所有寵物的名字
names, err := client.Pet.
Query().
Select(pet.FieldName).
Strings(ctx)
獲取所有寵物的名字和年齡
var v []struct {
Age int `json:"age"`
Name string `json:"name"`
}
err := client.Pet.
Query().
Select(pet.FieldAge, pet.FieldName).
Scan(ctx, &v)
if err != nil {
log.Fatal(err)
}
Delete One
這個用於如果我們已經通過client查詢到了一個entity,然後想要刪除這條記錄:
err := client.User.
DeleteOne(a8m).
Exec(ctx)
Delete by ID.
err := client.User.
DeleteOneID(id).
Exec(ctx)
Delete Many
使用斷言進行刪除
err := client.File.
Delete().
Where(file.UpdatedAtLT(date))
Exec(ctx)
Mutation
通過 entc init 生成的每個schema 都有自己的mutaion,例如我們通過 entc init User Pet, 在通過go generate ./ent 生成的程式碼中有 ent/mutation.go
在該檔案中定義了:
.....
// UserMutation represents an operation that mutate the Users
// nodes in the graph.
type UserMutation struct {
config
op Op
typ string
id *int
name *string
age *int
addage *int
clearedFields map[string]struct{}
done bool
oldValue func(context.Context) (*User, error)
}
.....
// PetMutation represents an operation that mutate the Pets
// nodes in the graph.
type PetMutation struct {
config
op Op
typ string
id *int
name *string
age *int
addage *int
clearedFields map[string]struct{}
done bool
oldValue func(context.Context) (*Pet, error)
}
例如,所有的User
builders都共享相同的UserMutaion 物件,左右的builder 型別都繼承通用的ent.Mutation
介面.
這裡所說的 user builders,拿User schema來說指的是UserCreate
、UserDelete
、UserQuery
、UserUpdate
物件,go generate 生成的程式碼中,我們可以到
./ent/user_create.go、./ent/user_delete.go、./ent/user_query.go、./ent/user_update.go
檔案中看到如下定義:
// ./ent/user_create.go
// UserCreate is the builder for creating a User entity.
type UserCreate struct {
config
mutation *UserMutation
hooks []Hook
}
//./ent/user_delete.go
// UserDelete is the builder for deleting a User entity.
type UserDelete struct {
config
hooks []Hook
mutation *UserMutation
predicates []predicate.User
}
// ./ent/user_query.go
// UserQuery is the builder for querying User entities.
type UserQuery struct {
config
limit *int
offset *int
order []OrderFunc
unique []string
predicates []predicate.User
// intermediate query (i.e. traversal path).
sql *sql.Selector
path func(context.Context) (*sql.Selector, error)
}
// ./ent/user_update.go
// UserUpdate is the builder for updating User entities.
type UserUpdate struct {
config
hooks []Hook
mutation *UserMutation
predicates []predicate.User
}
在下面的例子中,ent.UserCreate 和 ent.UserUpdate 都使用一個通用的方法對age 和name 列進行操作:
package main
import (
"context"
"log"
_ "github.com/go-sql-driver/mysql"
"github.com/peanut-cc/ent_orm_notes/aboutMutaion/ent"
)
func main() {
client, err := ent.Open("mysql", "root:123456@tcp(10.211.55.3:3306)/aboutMutaion?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)
}
Do(ctx, client)
}
func Do(ctx context.Context, client *ent.Client) {
creator := client.User.Create()
SetAgeName(creator.Mutation())
creator.SaveX(ctx)
updater := client.User.UpdateOneID(1)
SetAgeName(updater.Mutation())
updater.SaveX(ctx)
}
// SetAgeName sets the age and the name for any mutation.
func SetAgeName(m *ent.UserMutation) {
m.SetAge(32)
m.SetName("Ariel")
}
在某些情況下,你希望對多個不同的型別應用同一個方法,對於這種情況,要麼使用通用的ent.Mutation 介面,或者自己實現一個介面,程式碼如下:
func Do2(ctx context.Context, client *ent.Client) {
creator1 := client.User.Create().SetAge(18)
SetName(creator1.Mutation(), "a8m")
creator1.SaveX(ctx)
creator2 := client.Pet.Create().SetAge(16)
SetName(creator2.Mutation(), "pedro")
creator2.SaveX(ctx)
}
// SetNamer wraps the 2 methods for getting
// and setting the "name" field in mutations.
type SetNamer interface {
SetName(string)
Name() (string, bool)
}
func SetName(m SetNamer, name string) {
if _, exist := m.Name(); !exist {
m.SetName(name)
}
}
Graph Traversal
在這個部分的例子中會使用如下的Graph
上面的遍歷從一個 Group 實體開始,繼續到它的 admin (edge) ,繼續到它的朋友(edge) ,獲取他們的寵物(edge) ,獲取每個寵物的朋友(edge) ,並請求它們的主人
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
}
下面的遍歷如何?
我們希望得到所有寵物(entities)的所有者(edge)是朋友(edge)的一些群管理員(edge)。
func Traverse2(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
}
上面的查詢中,查詢所有的寵物,條件是: 寵物要有主人,同時寵物的主人是要有朋友,同時該主人還要屬於管理員
Eager Loading
ent 支援通過它們的edges 查詢,並將關聯的entities 新增到返回的物件中
通過下面的例子理解:
查詢上面關係中所有使用者和它們的寵物,程式碼如下:
func edgerLoading(ctx context.Context, client *ent.Client) {
users, err := client.User.Query().WithPets().All(ctx)
if err != nil {
log.Fatalf("user query failed:%v", err)
}
log.Println(users)
for _, u := range users {
for _, p := range u.Edges.Pets {
log.Printf("user (%v) -- > Pet (%v)\n", u.Name, p.Name)
}
}
}
完整的程式碼在:https://github.com/peanut-cc/ent_orm_notes/graph_traversal
查詢的結果如下:
2020/09/01 20:09:07 [User(id=1, age=29, name=Dan) User(id=2, age=30, name=Ariel) User(id=3, age=37, name=Alex) User(id=4, age=18, name=peanut)]
2020/09/01 20:09:07 user (Ariel) -- > Pet (Pedro)
2020/09/01 20:09:07 user (Ariel) -- > Pet (Xabi)
2020/09/01 20:09:07 user (Alex) -- > Pet (Coco)
預載入允許查詢多個關聯,包括巢狀關聯,還可以過濾,排序或限制查詢結果,例如:
func edgerLoading2(ctx context.Context, client *ent.Client) {
users, err := client.User.
Query().
Where(
user.AgeGT(18),
).
WithPets().
WithGroups(func(q *ent.GroupQuery) {
q.Limit(5)
q.WithUsers().Limit(5)
}).All(ctx)
if err != nil {
log.Fatalf("user query failed:%v", err)
}
log.Println(users)
for _, u := range users {
for _, p := range u.Edges.Pets {
log.Printf("user (%v) --> Pet (%v)\n", u.Name, p.Name)
}
for _, g := range u.Edges.Groups {
log.Printf("user (%v) -- Group (%v)\n", u.Name, g.Name)
}
}
}
每個query-builder都有一個方法列表,其形式為 With<E>(...func(<N>Query))
<E>
代表邊緣名稱(像WithGroups
) ,< N>
代表邊緣型別(像GroupQuery
)。
注意,只有 SQL 方言支援這個特性
Aggregation
Group By
按所有使用者的姓名和年齡欄位分組,並計算其總年齡。
package main
import (
"context"
"log"
"github.com/peanut-cc/ent_orm_notes/groupBy/ent/user"
_ "github.com/go-sql-driver/mysql"
"github.com/peanut-cc/ent_orm_notes/groupBy/ent"
)
func main() {
client, err := ent.Open("mysql", "root:123456@tcp(10.211.55.3:3306)/groupBy?parseTime=True",
ent.Debug())
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)
}
GenData(ctx, client)
Do(ctx, client)
}
func GenData(ctx context.Context, client *ent.Client) {
client.User.Create().SetName("peanut").SetAge(18).SaveX(ctx)
client.User.Create().SetName("jack").SetAge(20).SaveX(ctx)
client.User.Create().SetName("steve").SetAge(22).SaveX(ctx)
client.User.Create().SetName("peanut-cc").SetAge(18).SaveX(ctx)
client.User.Create().SetName("jack-dd").SetAge(18).SaveX(ctx)
}
func Do(ctx context.Context, client *ent.Client) {
var v []struct {
Name string `json:"name"`
Age int `json:"age"`
Sum int `json:"sum"`
Count int `json:"count"`
}
client.User.
Query().
GroupBy(
user.FieldName, user.FieldAge,
).
Aggregate(
ent.Count(),
ent.Sum(user.FieldAge),
).
ScanX(ctx, &v)
log.Println(v)
}
按一個欄位分組,例子如下:
func Do2(ctx context.Context, client *ent.Client) {
names := client.User.Query().GroupBy(user.FieldName).StringsX(ctx)
log.Println(names)
}
Predicates
Field Predicates
- Bool:
- =, !=
- Numberic:
- =, !=, >, <, >=, <=,
- IN, NOT IN
- Time:
- =, !=, >, <, >=, <=
- IN, NOT IN
- String:
- =, !=, >, <, >=, <=
- IN, NOT IN
- Contains, HasPrefix, HasSuffix
- ContainsFold, EqualFold (SQL specific)
- Optional fields:
- IsNil, NotNil
Edge Predicates
HasEdge 例如,查詢所有寵物的所有者,使用:
client.Pet.
Query().
Where(pet.HasOwner()).
All(ctx)
HasEdgeWith
client.Pet.
Query().
Where(pet.HasOwnerWith(user.Name("a8m"))).
All(ctx)
Negation (NOT)
client.Pet.
Query().
Where(pet.Not(pet.NameHasPrefix("Ari"))).
All(ctx)
Disjunction (OR)
client.Pet.
Query().
Where(
pet.Or(
pet.HasOwner(),
pet.Not(pet.HasFriends()),
)
).
All(ctx)
Conjunction (AND)
client.Pet.
Query().
Where(
pet.And(
pet.HasOwner(),
pet.Not(pet.HasFriends()),
)
).
All(ctx)
Custom Predicates
如果想編寫自己的特定於方言的邏輯,Custom predicates可能很有用。
pets := client.Pet.
Query().
Where(predicate.Pet(func(s *sql.Selector) {
s.Where(sql.InInts(pet.OwnerColumn, 1, 2, 3))
})).
AllX(ctx)
Paging And Ordering
Limit
將查詢結果限制為 n 個實體。
users, err := client.User.
Query().
Limit(n).
All(ctx)
Offset
設定從查詢返回的第一個最大數量。
users, err := client.User.
Query().
Offset(10).
All(ctx)
Ordering
Order 返回按一個或多個欄位的值排序的實體。
users, err := client.User.Query().
Order(ent.Asc(user.FieldName)).
All(ctx)