Merge pull request #551 from airblade/fix_mysql_text_too_short

In MySQL, use longtext instead of text

CHANGELOG.md

@@ -65,6 +65,8 @@ If you depend on the `RSpec` or `Cucumber` helpers, you will need to [manually l
     to `PaperTrail::Serializers::YAML`.
   - Both `PaperTrail.config` and `PaperTrail.configure` are now identical, and will both return the `PaperTrail::Config`
     instance and also yield it if a block is provided.
+  - [#248](https://github.com/airblade/paper_trail/issues/248) - The migrations
+    created by the generator now use `longtext` instead of `text` in MySQL.
 
 ## 3.0.8
 

lib/generators/paper_trail/templates/add_object_changes_to_versions.rb

@@ -1,5 +1,10 @@
 class AddObjectChangesToVersions < ActiveRecord::Migration
+
+  # The largest text column available in all supported RDBMS.
+  # See `create_versions.rb` for details.
+  TEXT_BYTES = 1_073_741_823
+
   def change
-    add_column :versions, :object_changes, :text
+    add_column :versions, :object_changes, :text, limit: TEXT_BYTES
   end
 end

lib/generators/paper_trail/templates/create_versions.rb

@@ -1,11 +1,18 @@
 class CreateVersions < ActiveRecord::Migration
+
+  # The largest text column available in all supported RDBMS is
+  # 1024^3 - 1 bytes, roughly one gibibyte.  We specify a size
+  # so that MySQL will use `longtext` instead of `text`.  Otherwise,
+  # when serializing very large objects, `text` might not be big enough.
+  TEXT_BYTES = 1_073_741_823
+
   def change
     create_table :versions do |t|
       t.string   :item_type, :null => false
       t.integer  :item_id,   :null => false
       t.string   :event,     :null => false
       t.string   :whodunnit
-      t.text     :object
+      t.text     :object,    :limit => TEXT_BYTES
       t.datetime :created_at
     end
     add_index :versions, [:item_type, :item_id]