Rails避免N + 1查询

Question

Given the following model relationship.

group has_many :members
member has_many :missions
mission has_one :game_set_mission
mission has_one :game_set, :through => :game_set_mission

Here is what I do

Given group is a Group object

# Add a new relationship in member.rb
has_many :game_sets, :through => :missions

# Get all game_set id
group.members.map{ |gc| gc.game_sets.pluck(:id) }

But it seems to occur N+1 query .

How do I improve my code?

Answer 1

Hope following one help you.

GameSet.includes(member: :group)
       .where('groups.id = ?', group.id)
       .pluck('game_sets.id')