Fix caching large snippet HTML content on MySQL databases

changelogs/unreleased/31647-fix-snippet-content_html.yml

+---
+title: Fix caching large snippet HTML content on MySQL databases
+merge_request: 11024
+author:

db/migrate/20170502091007_markdown_cache_limits_to_mysql.rb

+# rubocop:disable all
+require_relative 'markdown_cache_limits_to_mysql'

db/migrate/markdown_cache_limits_to_mysql.rb

+class MarkdownCacheLimitsToMysql < ActiveRecord::Migration
+  DOWNTIME = false
+
+  def up
+    return unless Gitlab::Database.mysql?
+
+    change_column :snippets, :content_html, :text, limit: 2147483647
+  end
+
+  def down
+    # no-op
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170426181740) do
+ActiveRecord::Schema.define(version: 20170502091007) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"

lib/tasks/gitlab/db.rake

@@ -65,6 +65,7 @@ namespace :gitlab do
       migrations = `git diff #{ref}.. --diff-filter=A --name-only -- db/migrate`.lines
         .map { |file| Rails.root.join(file.strip).to_s }
         .select { |file| File.file?(file) }
+        .select { |file| /\A[0-9]+.*\.rb\z/ =~ File.basename(file) }
 
       Gitlab::DowntimeCheck.new.check_and_print(migrations)
     end

lib/tasks/migrate/add_limits_mysql.rake

 require Rails.root.join('db/migrate/limits_to_mysql')
+require Rails.root.join('db/migrate/markdown_cache_limits_to_mysql')
 
 desc "GitLab | Add limits to strings in mysql database"
 task add_limits_mysql: :environment do
   puts "Adding limits to schema.rb for mysql"
   LimitsToMysql.new.up
+  MarkdownCacheLimitsToMysql.new.up
 end