On Tuesday, May 14, 2013 10:26:56 AM UTC+1, Илья Воронцов wrote:
>
> Are there any rationalies to make queries obtained by joining scope to be
> readonly? I read some old posts (pre-rails3) that joins adds additional
> columns to record so that ActiveRecord doesn't know how to update that
> fields, but actually I don't see that fields. For example I write model
> class Order < ActiveRecord::Base
> has_and_belongs_to_many :executors, class_name: 'Specialist',
> join_table: 'order_executors'
> scope :by_executor, ->(executor_id) {
> joins(:executors).where(specialists: {id: executor_id} ) }
> end
>
> and make query Order.by_executor(1) so that I get:
>
> Order Load (2.0ms) SELECT "orders".* FROM "orders" INNER JOIN
> "order_executors" ON "order_executors"."order_id" = "orders"."id" INNER
> JOIN "specialists" ON "specialists"."id" =
> "order_executors"."specialist_id" WHERE "specialists"."id" = 1
> => [#<Order id: 20, orderable_id: 11, orderable_type: "PlanDevelopment",
> client_id: 1, completion_status: "finished", created_at: "2013-05-13
> 20:48:19", updated_at: "2013-05-14 00:36:38", price:
> #<BigDecimal:67e5898,'0.14E2',9(36)>>]
>
> I see no additional columns but Order.by_executor(1).first.readonly? is
> true. Is that necessary?
>
> p.s. Yes I know that I can set readonly(false) or explicitly specify
> select clause - so that records won't become readonly. But I want to
> understand why this blocking behavior is necessary (if it is still true)
> and what damage will be possible without readonly mark? Also I don't
> understand, how can I shot myself if I explicitly set readonly(false).
>
This might be a hangover from the past - I think active record didn't use
to default to orders.* - the default select clause was select *.
The danger is only if you do select columns from the other tables. This can
either prevent saves (because your object has an attribute that doesn't
exist for the model) or mask existing data, eg if both of the joined tables
have a client_id column and you do select * then the activerecord object
will have a single client_id attribute that has only one of those values.
Fred
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