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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, :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
end
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