Class: CreateVersions

Inherits:
ActiveRecord::Migration
  • Object
show all
Defined in:
lib/generators/paper_trail/templates/create_versions.rb

Overview

This migration creates the ‘versions` table, the only schema PT requires. All other migrations PT provides are optional.

Constant Summary collapse

MYSQL_ADAPTERS =

Class names of MySQL adapters.

  • ‘MysqlAdapter` - Used by gems: `mysql`, `activerecord-jdbcmysql-adapter`.

  • ‘Mysql2Adapter` - Used by `mysql2` gem.

[
  "ActiveRecord::ConnectionAdapters::MysqlAdapter",
  "ActiveRecord::ConnectionAdapters::Mysql2Adapter"
].freeze
TEXT_BYTES =

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.

1_073_741_823

Instance Method Summary collapse

Instance Method Details

#change ⇒ Object 



18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
 
# File 'lib/generators/paper_trail/templates/create_versions.rb', line 18

def change
  create_table :versions, versions_table_options do |t|
    t.string   :item_type, item_type_options
    t.integer  :item_id,   null: false
    t.string   :event,     null: false
    t.string   :whodunnit
    t.text     :object, limit: TEXT_BYTES

    # Known issue in MySQL: fractional second precision
    # -------------------------------------------------
    #
    # MySQL timestamp columns do not support fractional seconds unless
    # defined with "fractional seconds precision". MySQL users should manually
    # add fractional seconds precision to this migration, specifically, to
    # the `created_at` column.
    # (https://dev.mysql.com/doc/refman/5.6/en/fractional-seconds.html)
    #
    # MySQL users should also upgrade to rails 4.2, which is the first
    # version of ActiveRecord with support for fractional seconds in MySQL.
    # (https://github.com/rails/rails/pull/14359)
    #
    t.datetime :created_at
  end
  add_index :versions, [:item_type, :item_id]
end