go-pg

Question

得到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"`
}

尝试这个 -

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 panic: pg: can't find dst value for model id="," 在线 https://github.com/go-pg/pg/blob/master/orm/model_table_m2m.go#L53。在尝试使用 delve 进行更深入的挖掘时，我发现 'prefix' 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",
]

我一直无法弄清楚如何覆盖此默认行为（Golang 和 go-pg 的新行为），我们将不胜感激，谢谢

Answer 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。

Answer 2

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

go-pg - pg：找不到模型 id="," 的 dst 值

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

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