Added drop_inheritance schema migration helper

Author: sigmen

lib/mti.rb

@@ -2,5 +2,5 @@
 require 'mti/railtie' if defined?(Rails::Railtie)
 
 module MTI
- class UnsupportedError < StandardError; end
+ class TableNotInheritedError < StandardError; end
 end

lib/mti/active_record/inheritable.rb

@@ -0,0 +1,37 @@
+module MTI
+ module ActiveRecord
+ module Inheritable
+ def drop_inheritance(table_name, parent_name)
+ unless inherited?(table_name, parent_name)
+ raise MTI::TableNotInheritedError, "#{table_name} not inherited from #{parent_name}"
+ end
+
+ execute(drop_inheritance_query(table_name, parent_name))
+ end
+
+ private
+
+ def inherited?(table_name, parent_name)
+ table_parents(table_name).any? { |x| x['relname'] == parent_name.to_s }
+ end
+
+ def table_parents(table_name)
+ execute(select_parents_query(table_name))
+ end
+
+ def drop_inheritance_query(table_name, parent_name)
+ "ALTER TABLE #{table_name} NO INHERIT #{parent_name};"
+ end
+
+ def select_parents_query(table_name)
+ <<-SQL
+ SELECT pg_namespace.nspname, pg_class.relname
+ FROM pg_catalog.pg_inherits
+ INNER JOIN pg_catalog.pg_class ON (pg_inherits.inhparent = pg_class.oid)
+ INNER JOIN pg_catalog.pg_namespace ON (pg_class.relnamespace = pg_namespace.oid)
+ WHERE inhrelid = '#{table_name}'::regclass
+ SQL
+ end
+ end
+ end
+end

lib/mti/active_record/schema_statements.rb

@@ -0,0 +1,51 @@
+require 'mti/active_record/inheritable'
+
+module MTI
+ module ActiveRecord
+ module SchemaStatements
+ include MTI::ActiveRecord::Inheritable
+
+ def create_table(table_name, options = {})
+ inherited_table = options.delete(:inherited_from)
+
+ prepare_options(inherited_table, options)
+
+ table_name = prepare_table_name(table_name, options)
+
+ super(table_name, options)
+ end
+
+ private
+
+ def prepare_options(inherited_table, options)
+ remove_pk_option(options)
+ add_inheritance_query(inherited_table, options)
+ end
+
+ def remove_pk_option(options)
+ return unless options[:inherited_from]
+
+ options[:id] = false
+ options.delete(:primary_key)
+ end
+
+ def add_inheritance_query(inherited_table, options)
+ return unless inherited_table
+
+ options[:options] = build_inherits_option(inherited_table)
+ end
+
+ def prepare_table_name(table_name, options)
+ schema = options.delete(:schema)
+
+ return table_name unless schema
+
+ "#{schema}.#{table_name}"
+ end
+
+ def build_inherits_option(inherited_table)
+ "INHERITS (#{inherited_table})"
+ end
+ end
+ end
+end

lib/mti/connection_adapter/postgresql/schema_statements.rb

@@ -1,12 +1,12 @@
-require 'mti/connection_adapter/postgresql/schema_statements'
+require 'mti/active_record/schema_statements'
 
 module MTI
  class Railtie < Rails::Railtie
- initializer 'mti' do |_app|
+ initializer 'mti' do
  ActiveSupport.on_load(:active_record) do
- adapter_klass = ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
+ adapter_klass = ::ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
 
- adapter_klass.prepend(ConnectionAdapter::PostgreSQL::SchemaStatements)
+ adapter_klass.prepend(MTI::ActiveRecord::SchemaStatements)
  end
  end
  end