Fix performance of home feed regeneration (#12084)

Fetching statuses from all followed accounts at once takes too long
within Postgres. Fetching them one by one and merging in Ruby
could be a lot less resource-intensive

Because the query for dynamically fetching the home timeline is so
heavy, we can no longer offer it when the home timeline is missing

spec/models/home_feed_spec.rb

@@ -34,11 +34,10 @@ RSpec.describe HomeFeed, type: :model do
         Redis.current.set("account:#{account.id}:regeneration", true)
       end
 
-      it 'gets statuses with ids in the range from database' do
+      it 'returns nothing' do
         results = subject.get(3)
 
-        expect(results.map(&:id)).to eq [10, 3, 2]
-        expect(results.first.attributes.keys).to include('id', 'updated_at')
+        expect(results.map(&:id)).to eq []
       end
     end
   end

spec/models/status_spec.rb

@@ -296,49 +296,6 @@ RSpec.describe Status, type: :model do
     end
   end
 
-  describe '.as_home_timeline' do
-    let(:account) { Fabricate(:account) }
-    let(:followed) { Fabricate(:account) }
-    let(:not_followed) { Fabricate(:account) }
-
-    before do
-      Fabricate(:follow, account: account, target_account: followed)
-
-      @self_status = Fabricate(:status, account: account, visibility: :public)
-      @self_direct_status = Fabricate(:status, account: account, visibility: :direct)
-      @followed_status = Fabricate(:status, account: followed, visibility: :public)
-      @followed_direct_status = Fabricate(:status, account: followed, visibility: :direct)
-      @not_followed_status = Fabricate(:status, account: not_followed, visibility: :public)
-
-      @results = Status.as_home_timeline(account)
-    end
-
-    it 'includes statuses from self' do
-      expect(@results).to include(@self_status)
-    end
-
-    it 'does not include direct statuses from self' do
-      expect(@results).to_not include(@self_direct_status)
-    end
-
-    it 'includes statuses from followed' do
-      expect(@results).to include(@followed_status)
-    end
-
-    it 'does not include direct statuses mentioning recipient from followed' do
-      Fabricate(:mention, account: account, status: @followed_direct_status)
-      expect(@results).to_not include(@followed_direct_status)
-    end
-
-    it 'does not include direct statuses not mentioning recipient from followed' do
-      expect(@results).not_to include(@followed_direct_status)
-    end
-
-    it 'does not include statuses from non-followed' do
-      expect(@results).not_to include(@not_followed_status)
-    end
-  end
-
   describe '.as_public_timeline' do
     it 'only includes statuses with public visibility' do
       public_status = Fabricate(:status, visibility: :public)