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Go SQLBoiler：查询关系并返回

来源：stackoverflow
2024-04-22 23:00:39
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问题内容

我正在使用 sqlboiler，如何查询关系并返回？我有两个单独的数据库表用于产品及其价格/金钱。我想查询两者并将它们一起返回到一个列表中，例如 getall 请求。

这是初始架构文件。

-- schema.sql

drop table if exists products cascade;
drop table if exists money;

create table products (
    id serial not null primary key,
    user_id int not null,
    name varchar(255) not null,
    description text not null,
    created_at timestamptz not null default now(),
    updated_at timestamptz not null default now(),
    deleted_at timestamptz
);

create table money (
    product_id int not null primary key,
    currency_code text not null default 'usd',
    units int not null,
    nanos int not null,
    created_at timestamptz not null default now(),
    updated_at timestamptz not null default now(),

    foreign key (product_id) references products (id) on delete cascade
);

create unique index idx_products_name
on products (name);

insert into products (user_id, name, description) values (1, 'something', 'this is something.');
insert into products (user_id, name, description) values (2, 'anything', 'this is anything.');

insert into money (product_id, currency_code, units, nanos) values (1, 'gbp', 450, 75);
insert into money (product_id, currency_code, units, nanos) values (2, 'cad', 9, 20);

...

func (s *server) index(context.context, *pb.empty) (*pb.indexproductresponse, error) {
    db := initpg()
    defer db.close()

    // make a slice of product type from generated protobuf
    products := make([]*pb.product, 0)

    // get all products (without price)
    ps, err := models.products().all(context.background(), db)
    logandreport(&pb.indexproductresponse{}, err)

    // how do i query each product's price from money table?
    // or
    // how do i query all money and assign to each related products?

    // fmt.println("@ ps here >", ps)

    // append queried products into products slice to return
    for _, p := range ps {
        products = append(products,
            &pb.product{
                id:          int32(p.id),
                name:        p.name,
                description: p.description,
                // i need to return/assign price information here.
                // i can do like this with gorm.
                //
                // price: &pb.money{
                //  currencycode: p.price.currencycode,
                //  units: p.price.units,
                //  nanos: p.price.nanos,
                // },
                userid:      int32(p.userid),
            })
    }

    return &pb.indexproductresponse{products: products}, nil
}

...

这是来自创建产品，但产品列表中的预期 graphql 结果几乎相同：

{
  "data": {
    "products": [
      {
        "id": "1",
        "name": "something",
        "description": "this is something.",
        "price": {
          "currencycode": "usd",
          "units": 9,
          "nanos": 93
        },
        "userid": "1"
      },
      {
        "id": "2",
        "name": "anything",
        "description": "this is anything.",
        "price": {
          "currencycode": "usd",
          "units": 24,
          "nanos": 56
        },
        "userid": "1"
      }
    ]
  },
...
}
...

这是产品服务的protobuf文件。

service ProductService {
  rpc Index(Empty) returns (IndexProductResponse) {}
}

message Money {
  // The 3-letter currency code defined in ISO 4217.
  string currency_code = 1;

  // The whole units of the amount.
  // For example if `currencyCode` is `"USD"`, then 1 unit is one US dollar.
  int64 units = 2;

  // Number of nano (10^-9) units of the amount.
  // The value must be between -999,999,999 and +999,999,999 inclusive.
  // If `units` is positive, `nanos` must be positive or zero.
  // If `units` is zero, `nanos` can be positive, zero, or negative.
  // If `units` is negative, `nanos` must be negative or zero.
  // For example $-1.75 is represented as `units`=-1 and `nanos`=-750,000,000.
  int32 nanos = 3;
}

message Product {
  int32 id = 1;
  string name = 2;
  string description = 3;
  Money price = 4;
  int32 user_id = 5;
}

message IndexProductResponse {
  repeated Product products = 1;
}

解决方案

您想要加载主要对象 product 及其所有相关的 money 行吗？

这应该可以做到：

products, err :=
    models.products(
        qm.load(models.productrels.productmoneys)
    ).all(context.background(), db)

这将生成并执行两个 sql 查询。第一个查询应该是

select * from "products"

并将检索所有产品。第二个查询应该类似于

select * from "money" where ("money"."product_id" in ($1,$2,$3))

并将收回所有产品的所有资金。 （in 子句的具体内容将取决于退回的产品数量。）

然后您应该能够访问相关行，如下所示：

products[0].R.ProductMoneys

注意：productrels 和/或 productmoneys 可能不是 sqlboiler 生成的确切名称。我不得不在这里猜测。确保检查生成的代码以获得正确的名称。

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