From 1db9d17756f7a5704f6f9f81ace155f4d98b684c Mon Sep 17 00:00:00 2001
From: Sam <sam.saffron@gmail.com>
Date: Mon, 5 Dec 2016 12:11:46 +1100
Subject: [PATCH] Make removal of topic columns more resilient to deploys

---
 app/controllers/application_controller.rb     | 26 +++++++++++++++++
 db/fixtures/009_users.rb                      |  2 +-
 db/fixtures/999_topics.rb                     | 29 +++++++++++++++++++
 .../20161205001727_add_topic_columns_back.rb  | 21 ++++++++++++++
 4 files changed, 77 insertions(+), 1 deletion(-)
 create mode 100644 db/migrate/20161205001727_add_topic_columns_back.rb

diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 795a46dfa4b..8323528ce47 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -110,6 +110,32 @@ class ApplicationController < ActionController::Base
     end
   end
 
+  def self.last_ar_cache_reset
+    @last_ar_cache_reset
+  end
+
+  def self.last_ar_cache_reset=(val)
+    @last_ar_cache_reset
+  end
+
+  rescue_from ActiveRecord::StatementInvalid do |e|
+
+    last_cache_reset = ApplicationController.last_ar_cache_reset
+
+    if e.message =~ /UndefinedColumn/ && (last_cache_reset.nil?  || last_cache_reset < 30.seconds.ago)
+      Rails.logger.warn "Clear Active Record cache cause schema appears to have changed!"
+
+      ApplicationController.last_ar_cache_reset = Time.zone.now
+
+      ActiveRecord::Base.connection.query_cache.clear
+      (ActiveRecord::Base.connection.tables - %w[schema_migrations]).each do |table|
+        table.classify.constantize.reset_column_information rescue nil
+      end
+    end
+
+    raise e
+  end
+
   class PluginDisabled < StandardError; end
 
   # Handles requests for giant IDs that throw pg exceptions
diff --git a/db/fixtures/009_users.rb b/db/fixtures/009_users.rb
index d65c8f2ef73..dd8a203e6b7 100644
--- a/db/fixtures/009_users.rb
+++ b/db/fixtures/009_users.rb
@@ -32,7 +32,7 @@ duration = Rails.env.production? ? 60 : 0
 if User.exec_sql("SELECT 1 FROM schema_migration_details
                   WHERE EXISTS(
                       SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS
-                      WHERE table_name = 'users' AND column_name = 'last_redirected_to_top_at'
+                      WHERE table_schema = 'public' AND table_name = 'users' AND column_name = 'last_redirected_to_top_at'
                     ) AND
                     name = 'MoveTrackingOptionsToUserOptions' AND
                     created_at < (current_timestamp at time zone 'UTC' - interval '#{duration} minutes')
diff --git a/db/fixtures/999_topics.rb b/db/fixtures/999_topics.rb
index cfe48615bcc..e46419fd20e 100644
--- a/db/fixtures/999_topics.rb
+++ b/db/fixtures/999_topics.rb
@@ -64,3 +64,32 @@ if seed_welcome_topics
                       skip_validations: true,
                       category: staff ? staff.name : nil)
 end
+
+
+
+# run this later, cause we need to make sure new application controller resilience is in place first
+duration = Rails.env.production? ? 60 : 0
+if Topic.exec_sql("SELECT 1 FROM schema_migration_details
+                  WHERE EXISTS(
+                      SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS
+                      WHERE table_schema = 'public' AND table_name = 'topics' AND column_name = 'inappropriate_count'
+                    ) AND
+                    name = 'AddTopicColumnsBack' AND
+                    created_at < (current_timestamp at time zone 'UTC' - interval '#{duration} minutes')
+                 ").to_a.length > 0
+
+
+  Topic.transaction do
+    STDERR.puts "Removing superflous topic columns!"
+    %w[
+    inappropriate_count
+    bookmark_count
+    off_topic_count
+    illegal_count
+    notify_user_count
+].each do |column|
+      User.exec_sql("ALTER TABLE topics DROP COLUMN IF EXISTS #{column}")
+    end
+
+  end
+end
diff --git a/db/migrate/20161205001727_add_topic_columns_back.rb b/db/migrate/20161205001727_add_topic_columns_back.rb
new file mode 100644
index 00000000000..d464c54a9e6
--- /dev/null
+++ b/db/migrate/20161205001727_add_topic_columns_back.rb
@@ -0,0 +1,21 @@
+class AddTopicColumnsBack < ActiveRecord::Migration
+
+  # This really sucks big time, we have no use for these columns yet can not remove them
+  # if we remove them then sites will be down during migration
+
+  def up
+     add_column :topics, :bookmark_count, :int
+     add_column :topics, :off_topic_count, :int
+     add_column :topics, :illegal_count, :int
+     add_column :topics, :inappropriate_count, :int
+     add_column :topics, :notify_user_count, :int
+  end
+
+  def down
+     remove_column :topics, :bookmark_count
+     remove_column :topics, :off_topic_count
+     remove_column :topics, :illegal_count
+     remove_column :topics, :inappropriate_count
+     remove_column :topics, :notify_user_count
+  end
+end