initial commit

Gemfile

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+source :rubygems
+
+gemspec
+
+group :development, :test do
+  platforms :mri_18 do
+    # required as linecache uses it but does not have it as a dep
+    gem "require_relative", "~> 1.0.1"
+    gem 'ruby-debug'
+  end
+
+  unless RUBY_VERSION == '1.9.3' && RUBY_PLATFORM !~ /darwin/
+    # will need to install ruby-debug19 manually for 1.9.3:
+    # gem install ruby-debug19 -- --with-ruby-include=$rvm_path/src/ruby-1.9.3-preview1
+    gem 'ruby-debug19', :platforms => :mri_19
+  end
+end
+

Gemfile.lock

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+PATH
+  remote: .
+  specs:
+    data_migrations (0.0.1)
+      activerecord
+
+GEM
+  remote: http://rubygems.org/
+  specs:
+    activemodel (3.0.9)
+      activesupport (= 3.0.9)
+      builder (~> 2.1.2)
+      i18n (~> 0.5.0)
+    activerecord (3.0.9)
+      activemodel (= 3.0.9)
+      activesupport (= 3.0.9)
+      arel (~> 2.0.10)
+      tzinfo (~> 0.3.23)
+    activesupport (3.0.9)
+    archive-tar-minitar (0.5.2)
+    arel (2.0.10)
+    builder (2.1.2)
+    columnize (0.3.4)
+    i18n (0.5.0)
+    linecache (0.46)
+      rbx-require-relative (> 0.0.4)
+    linecache19 (0.5.12)
+      ruby_core_source (>= 0.1.4)
+    pg (0.11.0)
+    rbx-require-relative (0.0.5)
+    require_relative (1.0.2)
+    ruby-debug (0.10.4)
+      columnize (>= 0.1)
+      ruby-debug-base (~> 0.10.4.0)
+    ruby-debug-base (0.10.4)
+      linecache (>= 0.3)
+    ruby-debug-base19 (0.11.25)
+      columnize (>= 0.3.1)
+      linecache19 (>= 0.5.11)
+      ruby_core_source (>= 0.1.4)
+    ruby-debug19 (0.11.6)
+      columnize (>= 0.3.1)
+      linecache19 (>= 0.5.11)
+      ruby-debug-base19 (>= 0.11.19)
+    ruby_core_source (0.1.5)
+      archive-tar-minitar (>= 0.5.2)
+    test_declarative (0.0.5)
+    tzinfo (0.3.29)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  data_migrations!
+  pg
+  require_relative (~> 1.0.1)
+  ruby-debug
+  ruby-debug19
+  test_declarative

LICENSE

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+MIT LICENSE
+
+Copyright (c)  Sven Fuchs <svenfuchs@artweb-design.de>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

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+# data\_migrations
+
+    class CreateRepositories < ActiveRecord::Migration
+      def self.up
+        create_table :tests do |t|
+          # ...
+        end
+
+        migrate_table :builds, :to => :tests |t|
+          t.where 'parent_id IS NULL'
+          t.move :number
+          t.copy :result, :to => :status
+          t.copy :commit, :result, :to => [:hash, :status]
+          t.copy :all, :except => :foo
+          t.exec 'UPDATE foo ...'
+        end
+      end
+
+      def self.down
+      end
+    end

Rakefile

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+require 'rake'
+require 'rake/testtask'
+
+Rake::TestTask.new do |t|
+  t.libs << 'lib'
+  t.pattern = 'test/**/*_test.rb'
+  t.verbose = false
+end
+
+task :default => :test

data_migrations.gemspec

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+# encoding: utf-8
+
+$:.unshift File.expand_path('../lib', __FILE__)
+require 'data_migrations/version'
+
+Gem::Specification.new do |s|
+  s.name         = "data_migrations"
+  s.version      = DataMigrations::VERSION
+  s.authors      = ["Sven Fuchs"]
+  s.email        = "svenfuchs@artweb-design.de"
+  s.homepage     = "https://github.com/svenfuchs/data_migrations"
+  s.summary      = "[summary]"
+  s.description  = "[description]"
+
+  s.files        = Dir['{lib/**/*,[A-Z]*}']
+  s.platform     = Gem::Platform::RUBY
+  s.require_path = 'lib'
+  s.rubyforge_project = '[none]'
+
+  s.add_dependency 'activerecord'
+  s.add_development_dependency 'test_declarative'
+  s.add_development_dependency 'pg'
+end

lib/data_migrations.rb

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+require 'active_record'
+require 'active_support/core_ext/module/delegation'
+require 'active_support/core_ext/array/extract_options'
+
+module DataMigrations
+  class Definition
+    attr_reader :source, :target, :instructions
+
+    def initialize(source, options = {})
+      @source = Table.new(source)
+      @target = Table.new(options[:to])
+      @instructions = []
+
+      yield self
+    end
+
+    def condition(condition = nil)
+      condition ? @condition = condition : @condition
+    end
+    alias :where :condition
+
+    def move(*columns)
+      options = columns.extract_options!
+      instructions << Move.new(self, columns, options)
+    end
+
+    def copy(*columns)
+      options = columns.extract_options!
+      instructions << Copy.new(self, columns, options)
+    end
+
+    def exec(sql)
+      instructions << Exec.new(self, sql)
+    end
+  end
+
+  class Table
+    delegate :connection, :to => :'ActiveRecord::Base'
+
+    attr_reader :name
+
+    def initialize(name)
+      @name = name
+    end
+
+    def columns
+      @columns ||= connection.columns(name)
+    end
+
+    def column(name)
+      columns.detect { |column| column.name.to_s == name.to_s } || raise_column_not_found(name)
+    end
+
+    def quoted_name
+      connection.quote_table_name(name)
+    end
+
+    def raise_column_not_found(name)
+      raise "could not find column #{name} on #{self.name}"
+    end
+  end
+
+  class Column
+    attr_reader :table, :name, :alias
+
+    def initialize(table, name, alias_)
+      @table = table
+      @name  = name
+      @alias = alias_
+    end
+
+    def aliased
+      self.alias ? "#{quote(name)} AS #{quote(self.alias)}" : quote(name)
+    end
+
+    def definition
+      [quote(self.alias || name), type].join(' ')
+    end
+
+    def type
+      column.sql_type
+    end
+
+    def column
+      @column ||= table.column(name)
+    end
+
+    def quoted_name
+      quote(name)
+    end
+
+    def quote(name)
+      ActiveRecord::Base.connection.quote_column_name(name)
+    end
+  end
+
+  class Instruction
+    delegate :connection, :to => :'ActiveRecord::Base'
+    delegate :condition, :to => :definition
+
+    attr_reader :definition
+
+    def initialize(definition)
+      @definition = definition
+    end
+
+    def execute
+      statements.each { |statement| connection.execute(statement) }
+    end
+
+    def source
+      definition.source
+    end
+
+    def target
+      definition.target
+    end
+
+    def columns=(columns)
+      @columns = columns.map { |column, alias_| Column.new(definition.source, column, alias_) }
+    end
+
+    def aliased_column_names
+      columns.map(&:aliased).join(', ')
+    end
+
+    def column_definitions
+      columns.map(&:definition).join(', ')
+    end
+  end
+
+  class Copy < Instruction
+    attr_reader :columns, :options
+
+    def initialize(definition, columns, options)
+      super(definition)
+      self.columns = columns.zip(Array(options[:to]))
+    end
+
+    def statements
+      [insert_statement]
+    end
+
+    def insert_statement
+      statement = "INSERT INTO #{target.quoted_name} SELECT #{aliased_column_names} FROM #{source.quoted_name} "
+      statement << "WHERE #{condition} " if condition
+      statement << "AS t(#{column_definitions})"
+    end
+  end
+
+  class Move < Copy
+    def statements
+      super + drop_statements
+    end
+
+    def drop_statements
+      columns.map do |column|
+        "ALTER TABLE #{source.quoted_name} DROP COLUMN #{column.quoted_name}"
+      end
+    end
+  end
+
+  def Runner
+    attr_reader :definition
+
+    def initialize(definition)
+      @definition = definition
+    end
+
+    def run!
+    end
+  end
+end

lib/data_migrations/version.rb

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+module DataMigrations
+  VERSION = "0.0.1"
+end