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。

参考资料

https://entgo.io/docs/schema-indexes/