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migration.rb
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migration.rb
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require 'rubygems'
gem 'dm-core', '~>0.9.10'
require 'dm-core'
require 'benchmark'
require File.dirname(__FILE__) + '/sql'
module DataMapper
class DuplicateMigrationNameError < StandardError
def initialize(migration)
super("Duplicate Migration Name: '#{migration.name}', version: #{migration.position}")
end
end
class Migration
include SQL
attr_accessor :position, :name, :database, :adapter
def initialize( position, name, opts = {}, &block )
@position, @name = position, name
@options = opts
@database = DataMapper.repository(@options[:database] || :default)
@adapter = @database.adapter
case @adapter.class.to_s
when /Sqlite3/ then @adapter.extend(SQL::Sqlite3)
when /Mysql/ then @adapter.extend(SQL::Mysql)
when /Postgres/ then @adapter.extend(SQL::Postgresql)
else
raise "Unsupported Migration Adapter #{@adapter.class}"
end
@verbose = @options.has_key?(:verbose) ? @options[:verbose] : true
@up_action = lambda {}
@down_action = lambda {}
instance_eval &block
end
# define the actions that should be performed on an up migration
def up(&block)
@up_action = block
end
# define the actions that should be performed on a down migration
def down(&block)
@down_action = block
end
# perform the migration by running the code in the #up block
def perform_up
result = nil
if needs_up?
# TODO: fix this so it only does transactions for databases that support create/drop
# database.transaction.commit do
say_with_time "== Performing Up Migration ##{position}: #{name}", 0 do
result = @up_action.call
end
update_migration_info(:up)
# end
end
result
end
# un-do the migration by running the code in the #down block
def perform_down
result = nil
if needs_down?
# TODO: fix this so it only does transactions for databases that support create/drop
# database.transaction.commit do
say_with_time "== Performing Down Migration ##{position}: #{name}", 0 do
result = @down_action.call
end
update_migration_info(:down)
# end
end
result
end
# execute raw SQL
def execute(sql, *bind_values)
say_with_time(sql) do
@adapter.execute(sql, *bind_values)
end
end
def create_table(table_name, opts = {}, &block)
execute TableCreator.new(@adapter, table_name, opts, &block).to_sql
end
def drop_table(table_name, opts = {})
execute "DROP TABLE #{@adapter.send(:quote_table_name, table_name.to_s)}"
end
def modify_table(table_name, opts = {}, &block)
TableModifier.new(@adapter, table_name, opts, &block).statements.each do |sql|
execute(sql)
end
end
def create_index(table_name, *columns_and_options)
if columns_and_options.last.is_a?(Hash)
opts = columns_and_options.pop
else
opts = {}
end
columns = columns_and_options.flatten
opts[:name] ||= "#{opts[:unique] ? 'unique_' : ''}index_#{table_name}_#{columns.join('_')}"
execute <<-SQL.compress_lines
CREATE #{opts[:unique] ? 'UNIQUE ' : '' }INDEX #{quote_column_name(opts[:name])} ON
#{quote_table_name(table_name)} (#{columns.map { |c| quote_column_name(c) }.join(', ') })
SQL
end
# Orders migrations by position, so we know what order to run them in.
# First order by postition, then by name, so at least the order is predictable.
def <=> other
if self.position == other.position
self.name.to_s <=> other.name.to_s
else
self.position <=> other.position
end
end
# Output some text. Optional indent level
def say(message, indent = 4)
write "#{" " * indent} #{message}"
end
# Time how long the block takes to run, and output it with the message.
def say_with_time(message, indent = 2)
say(message, indent)
result = nil
time = Benchmark.measure { result = yield }
say("-> %.4fs" % time.real, indent)
result
end
# output the given text, but only if verbose mode is on
def write(text="")
puts text if @verbose
end
# Inserts or removes a row into the `migration_info` table, so we can mark this migration as run, or un-done
def update_migration_info(direction)
save, @verbose = @verbose, false
create_migration_info_table_if_needed
if direction.to_sym == :up
execute("INSERT INTO #{migration_info_table} (#{migration_name_column}) VALUES (#{quoted_name})")
elsif direction.to_sym == :down
execute("DELETE FROM #{migration_info_table} WHERE #{migration_name_column} = #{quoted_name}")
end
@verbose = save
end
def create_migration_info_table_if_needed
save, @verbose = @verbose, false
unless migration_info_table_exists?
execute("CREATE TABLE #{migration_info_table} (#{migration_name_column} VARCHAR(255) UNIQUE)")
end
@verbose = save
end
# Quote the name of the migration for use in SQL
def quoted_name
"'#{name}'"
end
def migration_info_table_exists?
adapter.storage_exists?('migration_info')
end
# Fetch the record for this migration out of the migration_info table
def migration_record
return [] unless migration_info_table_exists?
@adapter.query("SELECT #{migration_name_column} FROM #{migration_info_table} WHERE #{migration_name_column} = #{quoted_name}")
end
# True if the migration needs to be run
def needs_up?
return true unless migration_info_table_exists?
migration_record.empty?
end
# True if the migration has already been run
def needs_down?
return false unless migration_info_table_exists?
! migration_record.empty?
end
# Quoted table name, for the adapter
def migration_info_table
@migration_info_table ||= quote_table_name('migration_info')
end
# Quoted `migration_name` column, for the adapter
def migration_name_column
@migration_name_column ||= quote_column_name('migration_name')
end
def quote_table_name(table_name)
# TODO: Fix this for 1.9 - can't use this hack to access a private method
@adapter.send(:quote_table_name, table_name.to_s)
end
def quote_column_name(column_name)
# TODO: Fix this for 1.9 - can't use this hack to access a private method
@adapter.send(:quote_column_name, column_name.to_s)
end
end
end