Gorm a two-way relation makes dirty data when inserting one model

Your Question

a two-way relation makes dirty data when inserting one model

how to reproduce:

open any db, use auto migrate to migrate tables

type Meeting struct {
    MeetingId    int       `gorm:"primaryKey"`
    MeetingNo    string    `gorm:"unique;not null"`
    BookedBy     int       `gorm:"not null"`
    BookedByName string    `gorm:"size:64;not null" comment:"who has booked this meeting"`
    MeetingState string    `gorm:"size:4;not null"`
    ScheduledAt  time.Time `gorm:"not null"`
    EndedAt      time.Time `gorm:"not null"`
    Users        []User    `gorm:"many2many:user_meeting_rule"`
}

type User struct {
    UserId    int       `gorm:"primaryKey"`
    Username  string    `gorm:"unique;not null"`
    Password  string    `gorm:"not null"`
    Phone     string    `gorm:"unique;not null"`
    Email     string    `gorm:"unique;not null"`
    CreatedAt time.Time `gorm:"not null"`
    Meetings  []Meeting `gorm:"many2many:user_meeting_rule"`
}

if i try to insert a meeting with users, gorm will first insert user in any ways

logs:

2025/07/03 11:54:57 C:/Users/matebook/Codes/rendezvous/internal/store/dbstore/meeting.go:39
[4.056ms] [rows:0] INSERT INTO "users" ("username","password","phone","email","created_at","user_id") VALUES ('ethan','1','2','1','2025-01-01 00:00:00',1) ON CONFLICT DO NOTHING RETURNING "user_id"

2025/07/03 11:54:57 C:/Users/matebook/Codes/rendezvous/internal/store/dbstore/meeting.go:39
[5.595ms] [rows:1] INSERT INTO "user_meeting_rule" ("meeting_meeting_id","user_user_id") VALUES (1,1) ON CONFLICT DO NOTHING

2025/07/03 11:54:57 C:/Users/matebook/Codes/rendezvous/internal/store/dbstore/meeting.go:39
[58.662ms] [rows:1] INSERT INTO "meetings" ("meeting_no","booked_by","booked_by_name","meeting_state","scheduled_at","ended_at") VALUES ('6VYkJ92S',1,'ethan','1','2006-01-02 15:04:05','2006-01-03 15:04:05') RETURNING "meeting_id"
{"time":"2025-07-03T11:54:57.3330097+08:00","id":"","remote_ip":"127.0.0.1","host":"127.0.0.1:8080","method":"POST","uri":"/api/v1/meeting","user_agent":"PostmanRuntime/7.44.1","status":200,"error":"","latency":68229100,"latency_human":"68.2291ms","bytes_in":123,"bytes_out":32}

What is expected?

it should only insert middle table, not inserting user