discourse/lib/migration/safe_migrate.rb

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module Migration; end
class Discourse::InvalidMigration < StandardError; end
class Migration::SafeMigrate
module SafeMigration
UNSAFE_VERSION = 20180321015220
@@enable_safe = true
def self.enable_safe!
@@enable_safe = true
end
def self.disable_safe!
@@enable_safe = false
end
def migrate(direction)
if direction == :up &&
version && version > UNSAFE_VERSION &&
@@enable_safe != false &&
!is_post_deploy_migration?
Migration::SafeMigrate.enable!
end
super
ensure
Migration::SafeMigrate.disable!
end
private
def is_post_deploy_migration?
method =
if self.respond_to?(:up)
:up
elsif self.respond_to?(:change)
:change
end
self.method(method).source_location.first.include?(
Discourse::DB_POST_MIGRATE_PATH
)
end
end
module NiceErrors
def migrate
super
rescue => e
if e.cause.is_a?(Discourse::InvalidMigration)
def e.cause
nil
end
def e.backtrace
super.reject do |frame|
frame =~ /safe_migrate\.rb/ || frame =~ /schema_migration_details\.rb/
end
end
raise e
else
raise e
end
end
end
def self.enable!
return if PG::Connection.method_defined?(:exec_migrator_unpatched)
PG::Connection.class_eval do
alias_method :exec_migrator_unpatched, :exec
alias_method :async_exec_migrator_unpatched, :async_exec
def exec(*args, &blk)
Migration::SafeMigrate.protect!(args[0])
exec_migrator_unpatched(*args, &blk)
end
def async_exec(*args, &blk)
Migration::SafeMigrate.protect!(args[0])
async_exec_migrator_unpatched(*args, &blk)
end
end
end
def self.disable!
return if !PG::Connection.method_defined?(:exec_migrator_unpatched)
PG::Connection.class_eval do
alias_method :exec, :exec_migrator_unpatched
alias_method :async_exec, :async_exec_migrator_unpatched
remove_method :exec_migrator_unpatched
remove_method :async_exec_migrator_unpatched
end
end
def self.patch_active_record!
ActiveSupport.on_load(:active_record) do
ActiveRecord::Migration.prepend(SafeMigration)
end
if defined?(ActiveRecord::Tasks::DatabaseTasks)
ActiveRecord::Tasks::DatabaseTasks.singleton_class.prepend(NiceErrors)
end
end
def self.protect!(sql)
if sql =~ /^\s*(?:drop\s+table|alter\s+table.*rename\s+to)\s+/i
$stdout.puts("", <<~STR)
WARNING
-------------------------------------------------------------------------------------
An attempt was made to drop or rename a table in a migration
SQL used was: '#{sql}'
Please generate a post deployment migration using `rails g post_migration` to drop
or rename the table.
This protection is in place to protect us against dropping tables that are currently
in use by live applications.
STR
raise Discourse::InvalidMigration, "Attempt was made to drop a table"
elsif sql =~ /^\s*alter\s+table.*(?:rename|drop)\s+/i
$stdout.puts("", <<~STR)
WARNING
-------------------------------------------------------------------------------------
An attempt was made to drop or rename a column in a migration
SQL used was: '#{sql}'
Please generate a post deployment migration using `rails g post_migration` to drop
or rename columns.
Note, to minimize disruption use self.ignored_columns = ["column name"] on your
ActiveRecord model, this can be removed 6 months or so later.
This protection is in place to protect us against dropping columns that are currently
in use by live applications.
STR
raise Discourse::InvalidMigration, "Attempt was made to rename or delete column"
end
end
end