fix: Use last_activity_at instead of updated_at for sorting (#1281)

Co-authored-by: Akash Srivastava <akash.srivastava.1911@gmail.com>

db/migrate/20200927135222_add_last_activity_at_to_conversation.rb

@@ -0,0 +1,35 @@
+class AddLastActivityAtToConversation < ActiveRecord::Migration[6.0]
+  def up
+    add_column :conversations,
+               :last_activity_at,
+               :datetime,
+               default: -> { 'CURRENT_TIMESTAMP' },
+               index: true
+
+    add_last_activity_at_to_conversations
+
+    change_column_null(:conversations, :last_activity_at, false)
+  end
+
+  def down
+    remove_column(:conversations, :last_activity_at)
+  end
+
+  private
+
+  def add_last_activity_at_to_conversations
+    ::Conversation.find_in_batches do |conversation_batch|
+      Rails.logger.info "Migrated till #{conversation_batch.first.id}\n"
+      conversation_batch.each do |conversation|
+        # rubocop:disable Rails/SkipsModelValidations
+        last_activity_at = if conversation.messages.last
+                             conversation.messages.last.created_at
+                           else
+                             conversation.created_at
+                           end
+        conversation.update_columns(last_activity_at: last_activity_at)
+        # rubocop:enable Rails/SkipsModelValidations
+      end
+    end
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_09_07_094912) do
+ActiveRecord::Schema.define(version: 2020_09_27_135222) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
@@ -226,6 +226,7 @@ ActiveRecord::Schema.define(version: 2020_09_07_094912) do
     t.bigint "contact_inbox_id"
     t.uuid "uuid", default: -> { "gen_random_uuid()" }, null: false
     t.string "identifier"
+    t.datetime "last_activity_at", default: -> { "CURRENT_TIMESTAMP" }, null: false
     t.index ["account_id", "display_id"], name: "index_conversations_on_account_id_and_display_id", unique: true
     t.index ["account_id"], name: "index_conversations_on_account_id"
     t.index ["contact_inbox_id"], name: "index_conversations_on_contact_inbox_id"