From 5afb92dbdcefacf8b8a06aa0451c67f1dfc6a501 Mon Sep 17 00:00:00 2001
From: Thorsten Eckel <te@znuny.com>
Date: Wed, 18 Oct 2017 11:21:10 +0200
Subject: [PATCH] Refactoring: Improved lookup of association IDs by performing
 one JOIN instead of multiple SELECTs. This is especially usefull for systems
 where the DB runs on a separated system.

---
 .../application_model/can_associations.rb     | 32 +++++++++++++++----
 app/models/concerns/has_groups.rb             |  2 +-
 test/unit/object_cache_test.rb                |  1 +
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/app/models/application_model/can_associations.rb b/app/models/application_model/can_associations.rb
index 2b5ac620a..058087300 100644
--- a/app/models/application_model/can_associations.rb
+++ b/app/models/application_model/can_associations.rb
@@ -108,13 +108,33 @@ returns
     cache = Cache.get(key)
     return cache if cache
 
-    # get relations
     attributes = self.attributes
-    self.class.reflect_on_all_associations.map do |assoc|
-      next if association_attributes_ignored.include?(assoc.name)
-      real_ids = assoc.name.to_s[0, assoc.name.to_s.length - 1] + '_ids'
-      next if !respond_to?(real_ids)
-      attributes[real_ids] = send(real_ids)
+    relevant   = %i(has_and_belongs_to_many has_many)
+    eager_load = []
+    pluck      = []
+    keys       = []
+    self.class.reflect_on_all_associations.each do |assoc|
+      next if relevant.exclude?(assoc.macro)
+
+      assoc_name = assoc.name
+      next if association_attributes_ignored.include?(assoc_name)
+
+      eager_load.push(assoc_name)
+      pluck.push("#{assoc.table_name}.id")
+      keys.push("#{assoc_name.to_s.singularize}_ids")
+    end
+
+    if eager_load.present?
+      ids = self.class.eager_load(eager_load)
+                .where(id: id)
+                .pluck(*pluck)
+
+      if keys.size > 1
+        values = ids.transpose.map(&:compact).map(&:uniq)
+        attributes.merge!( keys.zip( values ).to_h )
+      else
+        attributes[ keys.first ] = ids.compact
+      end
     end
 
     # special handling for group access associations
diff --git a/app/models/concerns/has_groups.rb b/app/models/concerns/has_groups.rb
index 4d420059a..9896ee3f0 100644
--- a/app/models/concerns/has_groups.rb
+++ b/app/models/concerns/has_groups.rb
@@ -10,7 +10,7 @@ module HasGroups
     after_create :check_group_access_buffer
     after_update :check_group_access_buffer
 
-    association_attributes_ignored :groups
+    association_attributes_ignored :groups, group_through_identifier
 
     has_many group_through_identifier
     has_many :groups, through: group_through_identifier do
diff --git a/test/unit/object_cache_test.rb b/test/unit/object_cache_test.rb
index 26d9b05ec..4ab4ee840 100644
--- a/test/unit/object_cache_test.rb
+++ b/test/unit/object_cache_test.rb
@@ -29,6 +29,7 @@ class ObjectCacheTest < ActiveSupport::TestCase
 
     user1.organization_id = nil
     user1.save
+    org.reload
 
     assets = org.assets({})
     assert_equal(org.member_ids.sort, assets[:Organization][org.id]['member_ids'].sort)