ent 基本使用四 图遍历查询

接上文，我们已经创建了基本的关系以及表实体，以下是通过图方式的查询

参考关系图

代码处理

• 创建图数据

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("Tesla").

  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("Mazda").

  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("Ford").

  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

}

• 查询组名称为github 的用户以及汽车

func QueryGithub(ctx context.Context, client *ent.Client) error {

 cars, err := client.Group.

  Query().

  Where(group.Name("GitHub")). // (Group(Name=GitHub),)

  QueryUsers(). // (User(Name=Ariel, Age=30),)

  QueryCars(). // (Car(Model=Tesla, RegisteredAt=<Time>), Car(Model=Mazda, RegisteredAt=<Time>),)

  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=Mazda, RegisteredAt=<Time>),)

 return nil

}

• 查询用户Ariel 的车

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("Mazda"), // 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

}

• 查询包含用户的组

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

}

​

查询sql

为了查看生成的sql，我启用了慢查询处理

set global long_query_time=0;

set global slow_query_log=1;

• 生成的sql
  以下是一个查询的sql,我进行了格式化

 

SELECT

    DISTINCT `cars`.`id`,

    `cars`.`model`,

    `cars`.`registered_at`

FROM

    `cars`

    JOIN (

        SELECT

            `users`.`id`

        FROM

            `users`

            JOIN (

                SELECT

                    `group_users`.`user_id`

                FROM

                    `group_users`

                    JOIN (

                        SELECT

                            `groups`.`id`

                        FROM

                            `groups`

                            JOIN (

                                SELECT

                                    `group_users`.`group_id`

                                FROM

                                    `group_users`

                                    JOIN `users` AS `t0` ON `group_users`.`user_id` = `t0`.`id`

                                WHERE

                                    `t0`.`id` = 10

                            ) AS `t1` ON `groups`.`id` = `t1`.`group_id`

                    ) AS `t1` ON `group_users`.`group_id` = `t1`.`id`

            ) AS `t1` ON `users`.`id` = `t1`.`user_id`

    ) AS `t1` ON `cars`.`owner_id` = `t1`.`id`

WHERE

    NOT (`cars`.`model` = 'Mazda');

 

 

查看查询计划

EXPLAIN SELECT DISTINCT `cars`.`id`, `cars`.`model`, `cars`.`registered_at` FROM `cars` JOIN (SELECT `users`.`id` FROM `users` JOIN (SELECT `group_users`.`user_id` FROM `group_users` JOIN (SELECT `groups`.`id` FROM `groups` JOIN (SELECT `group_users`.`group_id` FROM `group_users` JOIN `users` AS `t0` ON `group_users`.`user_id` = `t0`.`id` WHERE `t0`.`id` = 10) AS `t1` ON `groups`.`id` = `t1`.`group_id`) AS `t1` ON `group_users`.`group_id` = `t1`.`id`) AS `t1` ON `users`.`id` = `t1`.`user_id`) AS `t1` ON `cars`.`owner_id` = `t1`.`id` WHERE NOT (`cars`.`model` = 'Mazda');

 

说明：
从上边可以看出通过索引进行了优化，还是比较高效的

参考资料

https://entgo.io/docs/getting-started/
https://github.com/rongfengliang/ent-demo