特性开关

此框架提供了一系列代码生成特性，可以自行选择使用。

用法

特性开关可以通过 CLI 标志或作为参数提供给 gen 包。

CLI

go run entgo.io/ent/cmd/ent generate --feature privacy,entql ./ent/schema

Go

// +build ignore
package main
import (
    "log"
    "text/template"
    "entgo.io/ent/entc"
    "entgo.io/ent/entc/gen"
)
func main() {
    err := entc.Generate("./schema", &gen.Config{
        Features: []gen.Feature{
            gen.FeaturePrivacy,
            gen.FeatureEntQL,
        },
        Templates: []*gen.Template{
            gen.MustParse(gen.NewTemplate("static").
                Funcs(template.FuncMap{"title": strings.ToTitle}).
                ParseFiles("template/static.tmpl")),
        },
    })
    if err != nil {
        log.Fatalf("running ent codegen: %v", err)
    }
}

特性列表

隐私层

隐私层允许为数据库中实体的查询和变更操作配置隐私政策（通俗的来讲，就是希望不同权限的人只能看到属于自己的内容）。

This option can added to a project using the --feature privacy flag, and its full documentation exists in the privacy page.

EntQL过滤器

entql配置项在运行时为不同的查询构造器提供了通用的动态筛选功能。

This option can be added to a project using the --feature entql flag, and more information about it exists in the privacy page.

自动解决合并冲突

schema/snapshot配置项告诉entc (ent 代码生成) ，对最新结构 (schema) 生成一个快照，当用户的 结构 (schema) 不能构建时，自动使用生成的快照解决合并冲突。

This option can be added to a project using the --feature schema/snapshot flag, but please see ent/ent/issues/852 to get more context about it.

Schema配置

使用sql/schemaconfig 配置项，你能给关系数据库中的对象定义别名，并将其映射到模型上。 当你的模型并不都生活在一个数据库下，而是根据 Schema 而有所不同，这很有用。

This option can be added to a project using the --feature sql/schemaconfig flag. 在生成代码之后，你就可以使用新的配置项，比如：

c, err := ent.Open(dialect, conn, ent.AlternateSchema(ent.SchemaConfig{
    User: "usersdb",
    Car: "carsdb",
}))
c.User.Query().All(ctx) // SELECT * FROM `usersdb`.`users`
c.Car.Query().All(ctx)  // SELECT * FROM `carsdb`.`cars`

Row-level Locks

The sql/lock option lets configure row-level locking using the SQL SELECT ... FOR {UPDATE | SHARE} syntax.

This option can be added to a project using the --feature sql/lock flag.

tx, err := client.Tx(ctx)
if err != nil {
    log.Fatal(err)
}
tx.Pet.Query().
    Where(pet.Name(name)).
    ForUpdate().
    Only(ctx)
tx.Pet.Query().
    Where(pet.ID(id)).
    ForShare(
        sql.WithLockTables(pet.Table),
        sql.WithLockAction(sql.NoWait),
    ).
    Only(ctx)

Custom SQL Modifiers

The sql/modifier option lets add custom SQL modifiers to the builders and mutate the statements before they are executed.

This option can be added to a project using the --feature sql/modifier flag.

Example 1

client.Pet.
    Query().
    Modify(func(s *sql.Selector) {
        s.Select("SUM(LENGTH(name))")
    }).
    IntX(ctx)

The above code will produce the following SQL query:

SELECT SUM(LENGTH(name)) FROM `pet`

Example 2

var p1 []struct {
    ent.Pet
    NameLength int `sql:"length"`
}
client.Pet.Query().
    Order(ent.Asc(pet.FieldID)).
    Modify(func(s *sql.Selector) {
        s.AppendSelect("LENGTH(name)")
    }).
    ScanX(ctx, &p1)

The above code will produce the following SQL query:

SELECT `pet`.*, LENGTH(name) FROM `pet` ORDER BY `pet`.`id` ASC

Example 3

var v []struct {
    Count     int       `json:"count"`
    Price     int       `json:"price"`
    CreatedAt time.Time `json:"created_at"`
}
client.User.
    Query().
    Where(
        user.CreatedAtGT(x),
        user.CreatedAtLT(y),
    ).
    Modify(func(s *sql.Selector) {
        s.Select(
            sql.As(sql.Count("*"), "count"),
            sql.As(sql.Sum("price"), "price"),
            sql.As("DATE(created_at)", "created_at"),
        ).
        GroupBy("DATE(created_at)").
        OrderBy(sql.Desc("DATE(created_at)"))
    }).
    ScanX(ctx, &v)

The above code will produce the following SQL query:

SELECT
    COUNT(*) AS `count`,
    SUM(`price`) AS `price`,
    DATE(created_at) AS `created_at`
FROM
    `users`
WHERE
    `created_at` > x AND `created_at` < y
GROUP BY
    DATE(created_at)
ORDER BY
    DATE(created_at) DESC

Example 4

var gs []struct {
    ent.Group
    UsersCount int `sql:"users_count"`
}
client.Group.Query().
    Order(ent.Asc(group.FieldID)).
    Modify(func(s *sql.Selector) {
        t := sql.Table(group.UsersTable)
        s.LeftJoin(t).
            On(
                s.C(group.FieldID),
                t.C(group.UsersPrimaryKey[1]),
            ).
            // Append the "users_count" column to the selected columns.
            AppendSelect(
                sql.As(sql.Count(t.C(group.UsersPrimaryKey[1])), "users_count"),
            ).
            GroupBy(s.C(group.FieldID))
    }).
    ScanX(ctx, &gs)

The above code will produce the following SQL query:

SELECT
    `groups`.*,
    COUNT(`t1`.`group_id`) AS `users_count`
FROM
    `groups` LEFT JOIN `user_groups` AS `t1`
ON
    `groups`.`id` = `t1`.`group_id`
GROUP BY
    `groups`.`id`
ORDER BY
    `groups`.`id` ASC

Upsert

The sql/upsert option lets configure upsert and bulk-upsert logic using the SQL ON CONFLICT / ON DUPLICATE KEY syntax. For full documentation, go to the Upsert API.

This option can be added to a project using the --feature sql/upsert flag.

// Use the new values that were set on create.
id, err := client.User.
    Create().
    SetAge(30).
    SetName("Ariel").
    OnConflict().
    UpdateNewValues().
    ID(ctx)
// In PostgreSQL, the conflict target is required.
err := client.User.
    Create().
    SetAge(30).
    SetName("Ariel").
    OnConflictColumns(user.FieldName).
    UpdateNewValues().
    Exec(ctx)
// Bulk upsert is also supported.
client.User.
    CreateBulk(builders...).
    OnConflict(
        sql.ConflictWhere(...),
        sql.UpdateWhere(...),
    ).
    UpdateNewValues().
    Exec(ctx)
// INSERT INTO "users" (...) VALUES ... ON CONFLICT WHERE ... DO UPDATE SET ... WHERE ...