Ruby - Query another table in a model definition - ruby-on-rails

Question

I want to query another table in a model definition. For instance, I have a table called miq_user_roles and I want to query and retrievesettings column value.
I tried adding the following
has_many :miq_user_roles
but when I try the where condition where(:settings => nil)
I get the error service_template doesn't have settings column. How can I query miq_user_roles for settings instead of service_template
service_template has a column called miq_group_id and its the id of miq_user_rolestable.
Following is the actual model definition where I want to include miq_user_roles table.
class ServiceTemplate < ApplicationRecord
include SupportsFeatureMixin
DEFAULT_PROCESS_DELAY_BETWEEN_GROUPS = 120
GENERIC_ITEM_SUBTYPES = {
"custom" => N_("Custom"),
"vm" => N_("Virtual Machine"),
"playbook" => N_("Playbook"),
"hosted_database" => N_("Hosted Database"),
"load_balancer" => N_("Load Balancer"),
"storage" => N_("Storage")
}.freeze
SERVICE_TYPE_ATOMIC = 'atomic'.freeze
SERVICE_TYPE_COMPOSITE = 'composite'.freeze
RESOURCE_ACTION_UPDATE_ATTRS = [:dialog,
:dialog_id,
:fqname,
:configuration_template,
:configuration_template_id,
:configuration_template_type].freeze
include CustomActionsMixin
include ServiceMixin
include OwnershipMixin
include NewWithTypeStiMixin
include TenancyMixin
include ArchivedMixin
include CiFeatureMixin
include_concern 'Filter'
include_concern 'Copy'
validates :name, :presence => true
belongs_to :tenant
has_many :service_templates, :through => :service_resources, :source => :resource, :source_type => 'ServiceTemplate'
has_many :services
has_many :service_template_tenants, :dependent => :destroy
has_many :additional_tenants, :through => :service_template_tenants, :source => :tenant, :dependent => :destroy
has_one :picture, :dependent => :destroy, :as => :resource, :autosave => true
belongs_to :service_template_catalog
belongs_to :zone
belongs_to :currency, :inverse_of => false
has_many :dialogs, -> { distinct }, :through => :resource_actions
has_many :miq_schedules, :as => :resource, :dependent => :destroy
has_many :miq_requests, :as => :source, :dependent => :nullify
has_many :active_requests, -> { where(:request_state => MiqRequest::ACTIVE_STATES) }, :as => :source, :class_name => "MiqRequest"
virtual_column :type_display, :type => :string
virtual_column :template_valid, :type => :boolean
virtual_column :template_valid_error_message, :type => :string
virtual_column :archived, :type => :boolean
virtual_column :active, :type => :boolean
default_value_for :internal, false
default_value_for :service_type, SERVICE_TYPE_ATOMIC
default_value_for(:generic_subtype) { |st| 'custom' if st.prov_type == 'generic' }
virtual_has_one :config_info, :class_name => "Hash"
scope :with_service_template_catalog_id, ->(cat_id) { where(:service_template_catalog_id => cat_id) }
scope :without_service_template_catalog_id, -> { where(:service_template_catalog_id => nil) }
scope :with_existent_service_template_catalog_id, -> { where.not(:service_template_catalog_id => nil) }
scope :displayed, -> { where(:display => true) }
scope :public_service_templates, -> { where(:display => true) }
supports :order do
unsupported_reason_add(:order, 'Service template does not belong to a service catalog') unless service_template_catalog
unsupported_reason_add(:order, 'Service template is not configured to be displayed') unless display
end
alias orderable? supports_order?
alias validate_order supports_order?
def self.with_tenant(tenant_id)
tenant = Tenant.find(tenant_id)
where(:tenant_id => tenant.ancestor_ids + [tenant_id])\
end

Answer 1

Add the table name:
where("miq_user_roles.settings" => nil)
Arel is nice, but you still have to use bits of SQL to get over issues like this.

Answer 2

You will have to use joins, to query on the associated table.
ServiceTemplate.joins(:miq_user_roles).where(miq_user_roles: { settings: nil })