Question

I have a 1 to many relationship where each group has multiple positions, i.e.

Group -1----N- Position

class Group { static hasMany = [postions: Position }

If I have a specific group instance, can’t I count directly how many positions it has? I.e. call some method group.positions.??

Thanks

Answer 1

As OverZealous said you can call group.positions.size() but it will be very expensive for a large number of Positions since it will load all of them into memory just to count them, and then throw them away.

If your Position class has a back-reference to its owning Group class, e.g. static belongsTo = [group: Group], then you can use this lightweight query:

def group = ...
int positionCount = Position.countByGroup(group)

If you don’t have a bidirectional relationship, you can get the count via HQL:

def group = ...
int positionCount = Group.executeQuery(
    'select count(pos) from Group g ' +
    'inner join g.positions pos where g=:g', [g: group])[0]