Gorm: Multiple joins are not working properly

Created on 22 Jan 2020 · 3Comments · Source: go-gorm/gorm

What version of Go are you using (`go version`)?

go1.13.6 linux/amd64

Which database and its version are you using?

PostgreSQL 12.1 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 9.2.0, 64-bit

The problem itself

I have the following struct:

type NoteCard struct {
    Id           int       `json:"id"`
    AuthorId     int       `json:"author_id"`
    AuthorName   string    `json:"author_name"`
    CategoryId   int       `json:"category_id"`
    CategoryName string    `json:"category_name"`
    SubjectId    int       `json:"subject_id"`
    SubjectName  string    `json:"subject_name"`
    TeacherId    int       `json:"teacher_id"`
    TeacherName  string    `json:"teacher_name"`
    PostedAt     time.Time `json:"posted_at"`
    Title        string    `json:"title"`
}

And the following code snippet:

func (api *API) GetNoteCards(c *gin.Context) {
    var noteCards []NoteCard

    searchItems := "notes.id, notes.author_id, users.name, notes.category_id, categories.name, notes.subject_id, subjects.name, " +
        "notes.teacher_id, teachers.name, notes.posted_at, notes.title"

    err := api.db.Table("notes").Select(searchItems).
        Joins("INNER JOIN users ON notes.author_id = users.id").
        Joins("INNER JOIN categories ON notes.category_id = categories.id").
        Joins("INNER JOIN subjects ON notes.subject_id = subjects.id").
        Joins("INNER JOIN teachers ON notes.teacher_id = teachers.id").
        Order("notes.posted_at DESC").
        Scan(&noteCards).Error

    if err != nil {
        log.Println(err)
    }

    if err := json.NewEncoder(c.Writer).Encode(noteCards); err != nil {
        log.Printf("Cannot encode note cards to JSON, error: %v\n", err)
    }
}

This code completes without errors, but the fields of joined tables (users, categories, subjects and teachers) are empty strings. At the same time, when I run this code in psql bash, it works perfectly correctly.

Is this a bug or am I doing something wrong?

gorm_v1

Source

on3dd

Most helpful comment

Preloads will help you. But generally it is an really epic fail that makes this lib fully unusable. E.g. I need a result sets 100000+ records, but Preloads are just selects with IN STATEMENT-s so there is always a limitation in size. Next obvious workaround is split into parallel chunks but breaks ordering.

dkul108 on 24 Jan 2020

👍3

All 3 comments

dkul108 on 24 Jan 2020

👍3

This issue will be automatically closed because it is marked as GORM V1 issue, we have released the public testing GORM V2 release and its documents https://v2.gorm.io/docs/ already, the testing release has been used in some production services for a while, and going to release the final version in following weeks, we are still actively collecting feedback before it, please open a new issue for any suggestion or problem, thank you

Also check out https://github.com/go-gorm/gorm/wiki/GORM-V2-Release-Note-Draft for how to use the public testing version and its changelog