Data fix migration to recompute unread conversations count. Fixes #8308

Current code that trigger incremental changes to users.unread_conversations_count
 appears to be correct. Believe the problem is a legacy data problem where data was
 incorrect from previous code issues and wasn't fixed previously.

 Test Plan:
 * setup a user with conversations
 * in the database, modify users.unread_conversations_count to be wrong (high or low)
 * run the migration and the conversation count should be corrected

Change-Id: Ibe5c1db2fb494e9800f89e9316f2a9519df77c43
Reviewed-on: https://gerrit.instructure.com/10702
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Jensen <jon@instructure.com>

db/migrate/20120502212620_fix_user_conversations_counts_for_all.rb

@@ -0,0 +1,13 @@
+class FixUserConversationsCountsForAll < ActiveRecord::Migration
+  tag :postdeploy
+  self.transactional = false
+
+  def self.up
+    DataFixup::RecomputeUnreadConversationsCount.send_later_if_production(:run)
+  end
+
+  def self.down
+    # The migration is non-destructive and only updates counts to reflect already existing data.
+    #raise ActiveRecord::IrreversibleMigration
+  end
+end

lib/data_fixup/recompute_unread_conversations_count.rb

@@ -0,0 +1,17 @@
+module DataFixup::RecomputeUnreadConversationsCount
+  def self.run
+    # Include "last_message_at IS NOT NULL" to prevent it from counting unread deleted messages.
+    User.find_ids_in_batches do |ids|
+      User.connection.execute(User.send(:sanitize_sql_array, [<<-SQL, ids]))
+        UPDATE users u SET unread_conversations_count = (
+          SELECT COUNT(*)
+          FROM conversation_participants p
+          WHERE p.workflow_state = 'unread'
+            AND p.user_id = u.id
+            AND p.last_message_at IS NOT NULL
+        )
+        WHERE id IN (?)
+      SQL
+    end
+  end
+end

spec/migrations/fix_user_conversations_counts_for_all_spec.rb

@@ -0,0 +1,99 @@
+#
+# Copyright (C) 2011 Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
+require File.expand_path(File.dirname(__FILE__) + '/../spec_helper.rb')
+require 'db/migrate/20120502212620_fix_user_conversations_counts_for_all.rb'
+
+describe FixUserConversationsCountsForAll do
+  describe "up" do
+    it "should fix incorrect entries and correctly count already correct entries" do
+      # Setup user with correct unread_conversations_count (2 unread convos)
+      u1 = user
+      2.times do
+        c = u1.initiate_conversation([u1.id], false)
+        c.add_message('Hello')
+        c.add_message('Hello again')
+        c.update_attribute(:workflow_state, 'unread')
+      end
+      # unread_conversations_count == 2
+
+      # Setup user with wrong unread_conversations_count (negative)
+      u2 = user
+      1.times do
+        c = u2.initiate_conversation([u2.id], false)
+        c.add_message('Hello')
+        c.add_message('Hello again')
+        c.update_attribute(:workflow_state, 'unread')
+      end
+      # unread_conversations_count == 1
+      u2.update_attribute(:unread_conversations_count, -3)
+
+      # Setup user with wrong unread_conversations_count (too many)
+      u3 = user
+      3.times do
+        c = u3.initiate_conversation([u3.id], false)
+        c.add_message('Hello')
+        c.add_message('Hello again')
+        c.update_attribute(:workflow_state, 'unread')
+      end
+      # unread_conversations_count == 3
+      u3.update_attribute(:unread_conversations_count, 10)
+
+      FixUserConversationsCountsForAll.up
+
+      u1.reload.unread_conversations_count.should == 2
+      u2.reload.unread_conversations_count.should == 1
+      u3.reload.unread_conversations_count.should == 3
+    end
+
+    it "should not count deleted entries" do
+      # Setup user with some deleted conversations
+      u1 = user
+      2.times do
+        c = u1.initiate_conversation([u1.id], false)
+        c.add_message('Hello')
+        c.add_message('Hello again')
+        c.update_attribute(:workflow_state, 'unread')
+      end
+      1.times do
+        c = u1.initiate_conversation([u1.id], false)
+        c.add_message('Deleted myself')
+        c.add_message('Empty yo')
+        c.update_attribute(:workflow_state, 'unread')
+        c.remove_messages(:all)         # delete conversation (and all messages)
+      end
+      # unread_conversations_count == 2
+
+      # Setup user with only deleted conversations (should have count 0)
+      u2 = user
+      3.times do
+        c = u2.initiate_conversation([u2.id], false)
+        c.add_message('Hello')
+        c.add_message('Hello again')
+        c.update_attribute(:workflow_state, 'unread')
+        c.remove_messages(:all)         # delete conversation (and all messages)
+      end
+      # unread_conversations_count == 0
+
+      FixUserConversationsCountsForAll.up
+
+      u1.reload.unread_conversations_count.should == 2
+      u2.reload.unread_conversations_count.should == 0
+    end
+  end
+end