go-pg - pg: 找不到模型 id="," 的 dst 值答案

【问题标题】：go-pg - pg: can't find dst value for model id=","go-pg - pg: 找不到模型 id="," 的 dst 值
【发布时间】：2017-12-24 09:48:02
【问题描述】：

获取pg: can't find dst value for model id=","

我定义了以下模型

// omitting fields which don't seem relevant to the issue
// corresponding queries also shortened as appropriate
type GrProduct struct {
    tableName        struct{} `sql:"gr_product"`
    ID               int64
    Name             string
// fk:Product,joinFK:Category given so that joins are made on category_id and product_id with gr_product_category_mapping
    Categories       []*GrCategory               `pg:",many2many:gr_product_category_mapping,fk:Product,joinFK:Category"`
    CategoryMappings []*GrProductCategoryMapping `pg:",fk:Product"`
}

type GrProductCategoryMapping struct {
    tableName  struct{} `sql:"gr_product_category_mapping"`
    ID         int64
    ProductID  int64 // product_id in db instead of gr_product_id
    CategoryID int // category id in db instead of gr_category_id
    IsPrimary  bool
}

type GrCategory struct {
    tableName                struct{} `sql:"gr_category"`
    ID                       int
    Name                     string
    Products                 []*GrProduct `pg:",many2many:gr_product_category_mapping,fk:Category,joinFK:Product"`
}

试试这个 -

p := models.GrProduct{}
if err := models.DB.Model(&p).
    Column("Categories").
    Where("id = ?", 10).
    Select(); err != nil {
    panic(err)
}

这些是进行的查询

SELECT
    "gr_product"."id",
    "gr_product"."name"  
FROM
    gr_product AS "gr_product" 
WHERE
    (
        id= 10
    );

SELECT
    gr_product_category_mapping.*,
    "gr_category"."id",
    "gr_category"."name"

FROM
    gr_category AS "gr_category" 
JOIN
    gr_product_category_mapping AS gr_product_category_mapping 
        ON (
            gr_product_category_mapping."product_id"
        ) IN (
            (
                10
            )
        ) 
WHERE
    (
        "gr_category"."id" = gr_product_category_mapping."category_id"
    );

我想我在https://github.com/go-pg/pg/blob/master/orm/model_table_m2m.go#L53 上收到了panic: pg: can't find dst value for model id=","。在尝试深入挖掘时，我发现“前缀”m.baseTable.ModelName+"_" 的计算结果为gr_product_，但可能应该是product_，因为columns 包含

map[string]string [
        "product_id": "10",
        "category_id": "48",
        "is_primary": "t",
]

我无法弄清楚如何覆盖这个默认行为（Golang 和 go-pg 都是新的），任何帮助将不胜感激，谢谢

【问题讨论】：

标签： postgresql go orm go-pg

【解决方案1】：

您应该能够使用sql 标记来覆盖默认列名。

type GrProductCategoryMapping struct {
    tableName  struct{} `sql:"gr_product_category_mapping"`
    ID         int64
    ProductID  int64 `sql:"product_id"`
    CategoryID int   `sql:"category_id"`
    IsPrimary  bool
}

阅读更多here。

【讨论】：

我会试试这个并告诉你，但ProductID 不代表product_id - *更新：这没有帮助
你说得对，这不能解决你的问题，我应该更仔细地阅读这个问题。

【解决方案2】：

这是一个在 v6.4.6 中修复的错误。这是相关问题 - https://github.com/go-pg/pg/issues/583

【讨论】：