From 7bd890fce08870d5dcc412ee54b00c9ebbc38c95 Mon Sep 17 00:00:00 2001
From: Alexander Lang <2173+langalex@users.noreply.github.com>
Date: Sun, 25 Feb 2024 17:44:40 +0100
Subject: [PATCH] add database_collection to models (#162)

this allows code using this library to detect and avoid n+1 requests when loading associated models:

if database_collection is set on a model, instead of loading just one associated model by its id, code should load all associated models for all models in database_collection.
---
 lib/couch_potato/database.rb            |  2 +
 lib/couch_potato/persistence.rb         |  2 +-
 lib/couch_potato/view/flex_view_spec.rb |  2 +
 spec/unit/database_spec.rb              | 63 +++++++++++++++++++++----
 spec/unit/flex_view_spec_spec.rb        | 27 +++++++++++
 5 files changed, 87 insertions(+), 9 deletions(-)

diff --git a/lib/couch_potato/database.rb b/lib/couch_potato/database.rb
index 9f3c7a9..2dc79f3 100644
--- a/lib/couch_potato/database.rb
+++ b/lib/couch_potato/database.rb
@@ -224,6 +224,7 @@ def process_view_results(results, spec)
       elsif processed_results.respond_to?(:each)
         processed_results.each do |document|
           document.database = self if document.respond_to?(:database=)
+          document.database_collection = processed_results if document.respond_to?(:database_collection=)
         end
       end
       processed_results
@@ -297,6 +298,7 @@ def bulk_load(ids)
       docs = response['rows'].map { |row| row['doc'] }.compact
       docs.each do |doc|
         doc.database = self if doc.respond_to?(:database=)
+        doc.database_collection = docs if doc.respond_to?(:database_collection=)
       end
     end
 
diff --git a/lib/couch_potato/persistence.rb b/lib/couch_potato/persistence.rb
index 7973e86..9cef8a1 100644
--- a/lib/couch_potato/persistence.rb
+++ b/lib/couch_potato/persistence.rb
@@ -27,7 +27,7 @@ def self.included(base) #:nodoc:
         ForbiddenAttributesProtection, Revisions
       base.send :include, Validation
       base.class_eval do
-        attr_accessor :_id, :_rev, :_deleted, :database
+        attr_accessor :_id, :_rev, :_deleted, :database, :database_collection
         alias_method :id, :_id
         alias_method :id=, :_id=
 
diff --git a/lib/couch_potato/view/flex_view_spec.rb b/lib/couch_potato/view/flex_view_spec.rb
index e1c2716..bb49b23 100644
--- a/lib/couch_potato/view/flex_view_spec.rb
+++ b/lib/couch_potato/view/flex_view_spec.rb
@@ -73,9 +73,11 @@ def reduce_count
         end
 
         def docs
+          all_docs = rows.map { |r| r['doc'] }
           rows.map do |row|
             doc = row['doc']
             doc.database = database if doc.respond_to?(:database=)
+            doc.database_collection = all_docs if doc.respond_to?(:database_collection=)
             doc
           end
         end
diff --git a/spec/unit/database_spec.rb b/spec/unit/database_spec.rb
index e836c9c..96eb0cf 100644
--- a/spec/unit/database_spec.rb
+++ b/spec/unit/database_spec.rb
@@ -56,6 +56,16 @@ class Child
     db.load '1'
   end
 
+  it 'does not set database_collection on the model' do
+    user = double('user', 'database_collection=': nil).as_null_object
+    allow(DbTestUser).to receive(:new).and_return(user)
+    allow(couchrest_db).to receive(:get).and_return DbTestUser.json_create({ JSON.create_id => 'DbTestUser' })
+    
+    db.load '1'
+
+    expect(user).not_to have_received(:database_collection=).with(db)
+  end
+
   it 'should load namespaced models' do
     allow(couchrest_db).to receive(:get).and_return Parent::Child.json_create({ JSON.create_id => 'Parent::Child' })
     expect(db.load('1').class).to eq(Parent::Child)
@@ -89,7 +99,7 @@ class Child
 
     it 'does not write itself to a document that has no database= method' do
       doc1 = double(:doc1)
-      allow(doc1).to receive(:respond_to?).with(:database=) { false }
+      allow(doc1).to receive(:respond_to?) { false }
       allow(couchrest_db).to receive(:bulk_load) do
         { 'rows' => [{ 'doc' => doc1 }] }
       end
@@ -99,6 +109,24 @@ class Child
       db.load(['1'])
     end
 
+    it 'sets database_collection on each of the documents' do
+      db.load(%w[1 2]).each do |doc|
+        expect(doc.database_collection).to eql([doc1, doc2])
+      end
+    end
+
+    it 'does not set database_collection on a document that has no database_collection= method' do
+      doc1 = double(:doc1)
+      allow(doc1).to receive(:respond_to?) { false }
+      allow(couchrest_db).to receive(:bulk_load) do
+        { 'rows' => [{ 'doc' => doc1 }] }
+      end
+
+      expect(doc1).not_to receive(:database_collection=)
+
+      db.load(['1'])
+    end
+
     it 'returns an empty array when passing an empty array' do
       expect(db.load([])).to eq([])
     end
@@ -336,7 +364,7 @@ def set_errors
     allow(CouchPotato::View::ViewQuery).to receive_messages(new: double('view query', query_view!: { 'rows' => [@result] }))
   end
 
-  it 'initialzes a view query with map/reduce/list/lib funtions' do
+  it 'initializes a view query with map/reduce/list/lib funtions' do
     allow(@spec).to receive_messages(design_document: 'design_doc', view_name: 'my_view',
                                      map_function: '<map_code>', reduce_function: '<reduce_code>',
                                      lib: { test: '<test_code>' },
@@ -355,7 +383,7 @@ def set_errors
     @db.view(@spec)
   end
 
-  it 'initialzes a view query with map/reduce/list funtions' do
+  it 'initializes a view query with map/reduce/list funtions' do
     allow(@spec).to receive_messages(design_document: 'design_doc', view_name: 'my_view',
                                      map_function: '<map_code>', reduce_function: '<reduce_code>',
                                      lib: nil, list_name: 'my_list', list_function: '<list_code>',
@@ -374,7 +402,7 @@ def set_errors
     @db.view(@spec)
   end
 
-  it 'initialzes a view query with only map/reduce/lib functions' do
+  it 'initializes a view query with only map/reduce/lib functions' do
     allow(@spec).to receive_messages(design_document: 'design_doc', view_name: 'my_view',
                                      map_function: '<map_code>', reduce_function: '<reduce_code>',
                                      list_name: nil, list_function: nil,
@@ -390,7 +418,7 @@ def set_errors
     @db.view(@spec)
   end
 
-  it 'initialzes a view query with only map/reduce functions' do
+  it 'initializes a view query with only map/reduce functions' do
     allow(@spec).to receive_messages(design_document: 'design_doc', view_name: 'my_view',
                                      map_function: '<map_code>', reduce_function: '<reduce_code>',
                                      lib: nil, list_name: nil, list_function: nil)
@@ -405,18 +433,37 @@ def set_errors
     @db.view(@spec)
   end
 
-  it 'sets itself on returned results that have an accessor' do
+  it 'sets itself on returned docs that have an accessor' do
+    allow(@result).to receive(:respond_to?).and_return(false)
     allow(@result).to receive(:respond_to?).with(:database=).and_return(true)
     expect(@result).to receive(:database=).with(@db)
     @db.view(@spec)
   end
 
-  it "does not set itself on returned results that don't have an accessor" do
-    allow(@result).to receive(:respond_to?).with(:database=).and_return(false)
+  it "does not set itself on returned docs that don't have an accessor" do
+    allow(@result).to receive(:respond_to?).and_return(false)
     expect(@result).not_to receive(:database=).with(@db)
     @db.view(@spec)
   end
 
+  it 'sets the result of the view call on each returned doc' do
+    allow(@result).to receive(:respond_to?).and_return(false)
+    allow(@result).to receive(:respond_to?).with(:database_collection=).and_return(true)
+    allow(@result).to receive(:database_collection=)
+
+    @db.view(@spec)
+
+    expect(@result).to have_received(:database_collection=).with([@result])
+  end
+
+  it "does not set the result of the view call on docs that don't have an accessor" do
+    allow(@result).to receive(:respond_to?).and_return(false)
+
+    @db.view(@spec)
+
+    expect(@result).not_to receive(:database_collection=).with([@result])
+  end
+
   it 'does not try to set itself on result sets that are not collections' do
     expect do
       allow(@spec).to receive_messages(process_results: 1)
diff --git a/spec/unit/flex_view_spec_spec.rb b/spec/unit/flex_view_spec_spec.rb
index b57c5be..bb4de87 100644
--- a/spec/unit/flex_view_spec_spec.rb
+++ b/spec/unit/flex_view_spec_spec.rb
@@ -15,3 +15,30 @@
     expect(result.reduce_count).to eq(0)
   end
 end
+
+RSpec.describe CouchPotato::View::FlexViewSpec::Results, '#docs' do
+  it 'sets the database on each doc' do
+    db = double('db')
+    doc = double('doc', 'database=': nil)
+
+    result = CouchPotato::View::FlexViewSpec::Results.new 'rows' => [{ 'doc' => doc }]
+    result.database = db
+
+    result.docs
+
+    expect(doc).to have_received(:database=).with(db)
+  end
+
+  it 'sets all docs as database_collection on each doc' do
+    doc = double('doc', 'database_collection=': nil)
+
+    result = CouchPotato::View::FlexViewSpec::Results.new 'rows' => [{ 'doc' => doc }]
+
+    result.docs
+
+    expect(doc).to have_received(:database_collection=).with([doc])
+  end
+
+  it 'returns the docs' do
+  end
+end
\ No newline at end of file