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migration_generator.rb
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migration_generator.rb
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module HoboFields
class MigrationGeneratorError < RuntimeError; end
class HabtmModelShim < Struct.new(:join_table, :foreign_keys, :connection)
def self.from_reflection(refl)
result = self.new
result.join_table = refl.options[:join_table].to_s
result.foreign_keys = [refl.primary_key_name.to_s, refl.association_foreign_key.to_s].sort
# this may fail in weird ways if HABTM is running across two DB connections (assuming that's even supported)
# figure that anybody who sets THAT up can deal with their own migrations...
result.connection = refl.active_record.connection
result
end
def table_name
self.join_table
end
def field_specs
i = 0
foreign_keys.inject({}) do |h, v|
# some trickery to avoid an infinite loop when FieldSpec#initialize tries to call model.field_specs
h[v] = FieldSpec.new(self, v, :integer, :position => i)
i += 1
h
end
end
def primary_key
false
end
def index_specs
[]
end
end
class MigrationGenerator
@ignore_models = []
@ignore_tables = []
class << self
attr_accessor :ignore_models, :ignore_tables, :disable_indexing
end
def self.run(renames={})
g = MigrationGenerator.new
g.renames = renames
g.generate
end
def initialize(ambiguity_resolver={})
@ambiguity_resolver = ambiguity_resolver
@drops = []
@renames = nil
end
attr_accessor :renames
def load_rails_models
if defined? RAILS_ROOT
Dir["#{RAILS_ROOT}/app/models/**/[a-z0-9_]*.rb"].each do |f|
_, filename = *f.match(%r{/app/models/([_a-z0-9/]*).rb$})
filename.camelize.constantize
end
end
end
# Returns an array of model classes that *directly* extend
# ActiveRecord::Base, excluding anything in the CGI module
def table_model_classes
load_rails_models
ActiveRecord::Base.send(:subclasses).reject {|c| (c.base_class != c) || c.name.starts_with?("CGI::") }
end
def self.connection
ActiveRecord::Base.connection
end
def connection; self.class.connection; end
def self.fix_native_types(types)
case connection.class.name
when /mysql/i
types[:integer][:limit] ||= 11
end
types
end
def self.native_types
@native_types ||= fix_native_types connection.native_database_types
end
def native_types; self.class.native_types; end
# list habtm join tables
def habtm_tables
reflections = Hash.new { |h, k| h[k] = Array.new }
ActiveRecord::Base.send(:subclasses).map do |c|
c.reflect_on_all_associations(:has_and_belongs_to_many).each do |a|
reflections[a.options[:join_table].to_s] << a
end
end
reflections
end
# Returns an array of model classes and an array of table names
# that generation needs to take into account
def models_and_tables
ignore_model_names = MigrationGenerator.ignore_models.*.to_s.*.underscore
all_models = table_model_classes
hobo_models = all_models.select { |m| m.try.include_in_migration && m.name.underscore.not_in?(ignore_model_names) }
non_hobo_models = all_models - hobo_models
db_tables = connection.tables - MigrationGenerator.ignore_tables.*.to_s - non_hobo_models.*.table_name
[hobo_models, db_tables]
end
# return a hash of table renames and modifies the passed arrays so
# that renamed tables are no longer listed as to_create or to_drop
def extract_table_renames!(to_create, to_drop)
if renames
# A hash of table renames has been provided
to_rename = {}
renames.each_pair do |old_name, new_name|
new_name = new_name[:table_name] if new_name.is_a?(Hash)
next unless new_name
if to_create.delete(new_name.to_s) && to_drop.delete(old_name.to_s)
to_rename[old_name.to_s] = new_name.to_s
else
raise MigrationGeneratorError, "Invalid table rename specified: #{old_name} => #{new_name}"
end
end
to_rename
elsif @ambiguity_resolver
@ambiguity_resolver.extract_renames!(to_create, to_drop, "table")
else
raise MigrationGeneratorError, "Unable to resolve migration ambiguities"
end
end
def extract_column_renames!(to_add, to_remove, table_name)
if renames
to_rename = {}
column_renames = renames._?[table_name.to_sym]
if column_renames
# A hash of table renames has been provided
column_renames.each_pair do |old_name, new_name|
if to_add.delete(new_name.to_s) && to_remove.delete(old_name.to_s)
to_rename[old_name.to_s] = new_name.to_s
else
raise MigrationGeneratorError, "Invalid rename specified: #{old_name} => #{new_name}"
end
end
end
to_rename
elsif @ambiguity_resolver
@ambiguity_resolver.extract_renames!(to_add, to_remove, "column", "#{table_name}.")
else
raise MigrationGeneratorError, "Unable to resolve migration ambiguities in table #{table_name}"
end
end
def always_ignore_tables
# TODO: figure out how to do this in a sane way and be compatible with 2.2 and 2.3 - class has moved
sessions_table = CGI::Session::ActiveRecordStore::Session.table_name if
defined?(CGI::Session::ActiveRecordStore::Session) &&
defined?(ActionController::Base) &&
ActionController::Base.session_store == CGI::Session::ActiveRecordStore
['schema_info', 'schema_migrations', sessions_table].compact
end
def generate
models, db_tables = models_and_tables
models_by_table_name = {}
models.each do |m|
if !models_by_table_name.has_key?(m.table_name)
models_by_table_name[m.table_name] = m
elsif m.superclass==models_by_table_name[m.table_name].superclass.superclass
# we need to ensure that models_by_table_name contains the
# base class in an STI hierarchy
models_by_table_name[m.table_name] = m
end
end
# generate shims for HABTM models
habtm_tables.each do |name, refls|
models_by_table_name[name] = HabtmModelShim.from_reflection(refls.first)
end
model_table_names = models_by_table_name.keys
to_create = model_table_names - db_tables
to_drop = db_tables - model_table_names - always_ignore_tables
to_change = model_table_names
to_rename = extract_table_renames!(to_create, to_drop)
renames = to_rename.map do |old_name, new_name|
"rename_table :#{old_name}, :#{new_name}"
end * "\n"
undo_renames = to_rename.map do |old_name, new_name|
"rename_table :#{new_name}, :#{old_name}"
end * "\n"
drops = to_drop.map do |t|
"drop_table :#{t}"
end * "\n"
undo_drops = to_drop.map do |t|
revert_table(t)
end * "\n\n"
creates = to_create.map do |t|
create_table(models_by_table_name[t])
end * "\n\n"
undo_creates = to_create.map do |t|
"drop_table :#{t}"
end * "\n"
changes = []
undo_changes = []
to_change.each do |t|
model = models_by_table_name[t]
table = to_rename.key(t) || model.table_name
if table.in?(db_tables)
change, undo = change_table(model, table)
changes << change
undo_changes << undo
end
end
up = [renames, drops, creates, changes].flatten.reject(&:blank?) * "\n\n"
down = [undo_changes, undo_renames, undo_drops, undo_creates].flatten.reject(&:blank?) * "\n\n"
[up, down]
end
def create_table(model)
longest_field_name = model.field_specs.values.map { |f| f.sql_type.to_s.length }.max
if model.primary_key != "id"
if model.primary_key
primary_key_option = ", :primary_key => :#{model.primary_key}"
else
primary_key_option = ", :id => false"
end
end
(["create_table :#{model.table_name}#{primary_key_option} do |t|"] +
model.field_specs.values.sort_by{|f| f.position}.map {|f| create_field(f, longest_field_name)} +
["end"] + (MigrationGenerator.disable_indexing ? [] : create_indexes(model))) * "\n"
end
def create_indexes(model)
model.index_specs.map { |i| i.to_add_statement(model.table_name) }
end
def create_field(field_spec, field_name_width)
args = [field_spec.name.inspect] + format_options(field_spec.options, field_spec.sql_type)
" t.%-*s %s" % [field_name_width, field_spec.sql_type, args.join(', ')]
end
def change_table(model, current_table_name)
new_table_name = model.table_name
db_columns = model.connection.columns(current_table_name).index_by{|c|c.name}
key_missing = db_columns[model.primary_key].nil? && model.primary_key
db_columns -= [model.primary_key]
model_column_names = model.field_specs.keys.*.to_s
db_column_names = db_columns.keys.*.to_s
to_add = model_column_names - db_column_names
to_add += [model.primary_key] if key_missing && model.primary_key
to_remove = db_column_names - model_column_names
to_remove = to_remove - [model.primary_key.to_sym] if model.primary_key
to_rename = extract_column_renames!(to_add, to_remove, new_table_name)
db_column_names -= to_rename.keys
db_column_names |= to_rename.values
to_change = db_column_names & model_column_names
renames = to_rename.map do |old_name, new_name|
"rename_column :#{new_table_name}, :#{old_name}, :#{new_name}"
end
undo_renames = to_rename.map do |old_name, new_name|
"rename_column :#{new_table_name}, :#{new_name}, :#{old_name}"
end
to_add = to_add.sort_by {|c| model.field_specs[c].position }
adds = to_add.map do |c|
spec = model.field_specs[c]
args = [":#{spec.sql_type}"] + format_options(spec.options, spec.sql_type)
"add_column :#{new_table_name}, :#{c}, #{args * ', '}"
end
undo_adds = to_add.map do |c|
"remove_column :#{new_table_name}, :#{c}"
end
removes = to_remove.map do |c|
"remove_column :#{new_table_name}, :#{c}"
end
undo_removes = to_remove.map do |c|
revert_column(current_table_name, c)
end
old_names = to_rename.invert
changes = []
undo_changes = []
to_change.each do |c|
col_name = old_names[c] || c
col = db_columns[col_name]
spec = model.field_specs[c]
if spec.different_to?(col)
change_spec = {}
change_spec[:limit] = spec.limit unless spec.limit.nil? && col.limit.nil?
change_spec[:precision] = spec.precision unless spec.precision.nil?
change_spec[:scale] = spec.scale unless spec.scale.nil?
change_spec[:null] = spec.null unless spec.null && col.null
change_spec[:default] = spec.default unless spec.default.nil? && col.default.nil?
changes << "change_column :#{new_table_name}, :#{c}, " +
([":#{spec.sql_type}"] + format_options(change_spec, spec.sql_type, true)).join(", ")
back = change_column_back(current_table_name, col_name)
undo_changes << back unless back.blank?
else
nil
end
end.compact
index_changes, undo_index_changes = change_indexes(model, current_table_name)
[(renames + adds + removes + changes + index_changes) * "\n",
(undo_renames + undo_adds + undo_removes + undo_changes + undo_index_changes) * "\n"]
end
def change_indexes(model, old_table_name)
return [[],[]] if MigrationGenerator.disable_indexing || model.is_a?(HabtmModelShim)
new_table_name = model.table_name
existing_indexes = IndexSpec.for_model(model, old_table_name)
model_indexes = model.index_specs
add_indexes = model_indexes - existing_indexes
drop_indexes = existing_indexes - model_indexes
undo_add_indexes = []
undo_drop_indexes = []
add_indexes.map! do |i|
undo_add_indexes << drop_index(old_table_name, i.name)
i.to_add_statement(new_table_name)
end
drop_indexes.map! do |i|
undo_drop_indexes << i.to_add_statement(old_table_name)
drop_index(new_table_name, i.name)
end
# the order is important here - adding a :unique, for instance needs to remove then add
[drop_indexes + add_indexes, undo_add_indexes + undo_drop_indexes]
end
def drop_index(table, name)
"remove_index :#{table}, :name => :#{name}"
end
def format_options(options, type, changing=false)
options.map do |k, v|
unless changing
next if k == :limit && (type == :decimal || v == native_types[type][:limit])
next if k == :null && v == true
end
"#{k.inspect} => #{v.inspect}"
end.compact
end
def revert_table(table)
res = StringIO.new
ActiveRecord::SchemaDumper.send(:new, ActiveRecord::Base.connection).send(:table, table, res)
res.string.strip.gsub("\n ", "\n")
end
def column_options_from_reverted_table(table, column)
revert = revert_table(table)
if (md = revert.match(/\s*t\.column\s+"#{column}",\s+(:[a-zA-Z0-9_]+)(?:,\s+(.*?)$)?/m))
# Ugly migration
_, type, options = *md
elsif (md = revert.match(/\s*t\.([a-z_]+)\s+"#{column}"(?:,\s+(.*?)$)?/m))
# Sexy migration
_, type, options = *md
type = ":#{type}"
end
[type, options]
end
def change_column_back(table, column)
type, options = column_options_from_reverted_table(table, column)
"change_column :#{table}, :#{column}, #{type}#{', ' + options.strip if options}"
end
def revert_column(table, column)
type, options = column_options_from_reverted_table(table, column)
"add_column :#{table}, :#{column}, #{type}#{', ' + options.strip if options}"
end
end
end