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# frozen_string_literal: true
module LooseForeignKey
extend ActiveSupport::Concern
# This concern adds loose foreign key support to ActiveRecord models.
# Loose foreign keys allow delayed processing of associated database records
# with similar guarantees than a database foreign key.
#
# Prerequisites:
#
# To start using the concern, you'll need to install a database trigger to the parent
# table in a standard DB migration (not post-migration).
#
# > track_record_deletions(:projects)
#
# Usage:
#
# > class Ci::Build < ApplicationRecord
# >
# > loose_foreign_key :security_scans, :build_id, on_delete: :async_delete
# >
# > # associations can be still defined, the dependent options is no longer necessary:
# > has_many :security_scans, class_name: 'Security::Scan'
# >
# > end
#
# Options for on_delete:
#
# - :async_delete - deletes the children rows via an asynchronous process.
# - :async_nullify - sets the foreign key column to null via an asynchronous process.
#
# How it works:
#
# When adding loose foreign key support to the table, a DELETE trigger is installed
# which tracks the record deletions (stores primary key value of the deleted row) in
# a database table.
#
# These deletion records are processed asynchronously and records are cleaned up
# according to the loose foreign key definitions described in the model.
#
# The cleanup happens in batches, which reduces the likelyhood of statement timeouts.
#
# When all associations related to the deleted record are cleaned up, the record itself
# is deleted.
included do
class_attribute :loose_foreign_key_definitions, default: []
end
class_methods do
def loose_foreign_key(to_table, column, options)
symbolized_options = options.symbolize_keys
unless base_class?
raise <<~MSG
loose_foreign_key can be only used on base classes, inherited classes are not supported.
Please define the loose_foreign_key on the #{base_class.name} class.
MSG
end
on_delete_options = %i[async_delete async_nullify]
unless on_delete_options.include?(symbolized_options[:on_delete]&.to_sym)
raise "Invalid on_delete option given: #{symbolized_options[:on_delete]}. Valid options: #{on_delete_options.join(', ')}"
end
definition = ActiveRecord::ConnectionAdapters::ForeignKeyDefinition.new(
table_name.to_s,
to_table.to_s,
{
column: column.to_s,
on_delete: symbolized_options[:on_delete].to_sym
}
)
self.loose_foreign_key_definitions += [definition]
end
end
end
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