How to delete association (many2many)?-CodePudding

Strange behaviour deleting association happened. The query generated an extra condition which i did not add.

type Client struct {
    gorm.Model
    Name        string      `gorm:"unique;not null" validate:"required,min=1,max=30"`
    Kyc_status  string      `gorm:"not null" validate:"required,min=1,max=30"`
    Kyc_remarks string      `gorm:"default:null" validate:"omitempty,min=0,max=200"`
    Operators   []*Operator `gorm:"many2many:client_operators;"`
    Op_ids      []string    `gorm:"-:all" validate:"omitempty,dive,numeric"` // placeholder field, wont be part of table
}
type Operator struct {
    gorm.Model
    Title       string    `gorm:"unique;not null" validate:"required,min=1,max=100"`
    Email       string    `gorm:"not null" validate:"required,email"`
    Mobile      string    `gorm:"not null" validate:"required,min=7,max=15,numeric"`
    Last_online time.Time `gorm:"default:null" validate:"omitempty"`
    Last_ip     string    `gorm:"default:null" validate:"omitempty,ip"`
    Clients     []*Client `gorm:"many2many:client_operators;"`
    Cli_ids     []string  `gorm:"-:all" validate:"omitempty,dive,numeric"`
}

// find operators related to client
var client_query *Client
DBconnection.Where("id = ?", pk).Preload("Operators").First(&client_query)

// delete operators related to client
DBconnection.Model(&Client{}).Where("client_id = ?", pk).Association("Operators").Delete(&client_query.Operators)

I expect the deletion to be:

[2.000ms] [rows:0] DELETE FROM `client_operators` WHERE client_id = 5 AND `client_operators`.`operator_id` = 1

OR

[2.000ms] [rows:0] DELETE FROM `client_operators` WHERE `client_operators`.`client_id` = 5 AND `client_operators`.`operator_id` = 1

However it currently does:

[2.000ms] [rows:0] DELETE FROM `client_operators` WHERE client_id = 5 AND `client_operators`.`client_id` IN (NULL) AND `client_operators`.`operator_id` = 1

It adds the extra condition of " AND `client_operators`.`client_id` IN (NULL) "

I tried Association().Clear() and did not do anything too.

CodePudding user response：

This is happening because you're passing &Client{} to Model.

Looking at gorm docs you need to construct a client with a valid Id first like this:

type Client struct {
    gorm.Model
    Name        string      `gorm:"unique;not null" validate:"required,min=1,max=30"`
    Kyc_status  string      `gorm:"not null" validate:"required,min=1,max=30"`
    Kyc_remarks string      `gorm:"default:null" validate:"omitempty,min=0,max=200"`
    Operators   []*Operator `gorm:"many2many:client_operators;"`
    Op_ids      []string    `gorm:"-:all" validate:"omitempty,dive,numeric"` // placeholder field, wont be part of table
}
type Operator struct {
    gorm.Model
    Title       string    `gorm:"unique;not null" validate:"required,min=1,max=100"`
    Email       string    `gorm:"not null" validate:"required,email"`
    Mobile      string    `gorm:"not null" validate:"required,min=7,max=15,numeric"`
    Last_online time.Time `gorm:"default:null" validate:"omitempty"`
    Last_ip     string    `gorm:"default:null" validate:"omitempty,ip"`
    Clients     []*Client `gorm:"many2many:client_operators;"`
    Cli_ids     []string  `gorm:"-:all" validate:"omitempty,dive,numeric"`
}

// find operators related to client
var client_query *Client
DBconnection.Where("id = ?", pk).Preload("Operators").First(&client_query)



// delete operators related to client
DBconnection.Model(&Client{ID: pk}).Association("Operators").Delete(&client_query.Operators)