Any chance to add ability for custom fieldColumnProperty to interface which is used for select?

[wangxin688]

it's powerful to use column_property introduce in sqlalchemy for subquery some custom field.
eg: to query related object count is really easy to use.

[go-jet]

SqlAlchemy is an ORM and Jet is an SQLBuilder, so it is not possible to have such a feature built in as part of library. But you can extend jet models to achieve the same result. For instance you can wrap autogenerated model User to add a custom methods:

type User struct {
    model.User
}

func (u User) GetAddressCount() (int, error){
  stmt := SELECT(COUNT(STAR)).
    FROM(Address).
    WHERE(Address.UserID.EQ(u.User.ID))

  var dest int
  
  err := stmt.Query(db, &dest)
  //wrap err

  return dest, err  
}

To have complete ORM like experience you can also add a method to load user by id:

func (u *User) Load(id int64) error {
    stmt := SELECT(User.AllColumns).
        FROM(User).
        WHERE(User.ID.EQ(Int(id)))

    return stmt.Query(db, u)    
}

Now you can write:

var user User

err := user.Load(1234)

addressCount, err := user.GetAddressCount()