ent 基本使用八 索引
我们可以在ent 的schema 中定义index 可以方便的控制数据约束,使用索引可以加速我们的访问以及数据的唯一性处理
配置字段索引
- 多字段索引
package schema
import (
"github.com/facebookincubator/ent"
"github.com/facebookincubator/ent/schema/index"
)
// User holds the schema definition for the User entity.
type User struct {
ent.Schema
}
func (User) Indexes() []ent.Index {
return []ent.Index{
// non-unique index.
index.Fields("field1", "field2"),
// unique index.
index.Fields("first_name", "last_name").
Unique(),
}
}
- 配置单独字段索引
func (User) Fields() []ent.Field {
return []ent.Field{
field.String("phone").
Unique(),
}
}
边上的索引
可以根据字段和边的组成来配置索引。主要用例是在特定关系下的字段上设置唯一性，一个例子 
在上面的示例中，我们有一个City带有许多Street的，我们希望将街道名称设置为每个城市下唯一。
city schema
// City holds the schema definition for the City entity.
type City struct {
ent.Schema
}
// Fields of the City.
func (City) Fields() []ent.Field {
return []ent.Field{
field.String("name"),
}
}
// Edges of the City.
func (City) Edges() []ent.Edge {
return []ent.Edge{
edge.To("streets", Street.Type),
}
}
street schema
// Street holds the schema definition for the Street entity.
type Street struct {
ent.Schema
}
// Fields of the Street.
func (Street) Fields() []ent.Field {
return []ent.Field{
field.String("name"),
}
}
// Edges of the Street.
func (Street) Edges() []ent.Edge {
return []ent.Edge{
edge.From("city", City.Type).
Ref("streets").
Unique(),
}
}
// Indexes of the Street.
func (Street) Indexes() []ent.Index {
return []ent.Index{
index.Fields("name").
Edges("city").
Unique(),
}
}
- 测试代码
package main
import (
"context"
"fmt"
"log"
_ "github.com/go-sql-driver/mysql"
"github.com/rongfengliang/ent-index/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()
Do(ctx, client)
}
func Do(ctx context.Context, client *ent.Client) error {
// Unlike `Save`, `SaveX` panics if an error occurs.
tlv := client.City.
Create().
SetName("TLV").
SaveX(ctx)
nyc := client.City.
Create().
SetName("NYC").
SaveX(ctx)
// Add a street "ST" to "TLV".
client.Street.
Create().
SetName("ST").
SetCity(tlv).
SaveX(ctx)
// This operation will fail because "ST"
// is already created under "TLV".
_, err := client.Street.
Create().
SetName("ST").
SetCity(tlv).
Save(ctx)
if err == nil {
return fmt.Errorf("expecting creation to fail")
}
// Add a street "ST" to "NYC".
client.Street.
Create().
SetName("ST").
SetCity(nyc).
SaveX(ctx)
return nil
}
说明
索引当前仅支持SQL方言，不支持Gremlin。
