On Aug 31, 8:44 am, james <[email protected]> wrote:
> class Post < ActiveRecord::Base
> scope :published, lambda {
> where("posts.published_at IS NOT NULL AND posts.published_at
> <= ?", Time.zone.now)
> }
> end
>
> class User < ActiveRecord::Base
> scope :published, lambda {
> joins(:posts).group("users.id") & Post.published
> }
> end
>
> User.published.to_sql
> #=> SELECT users.* FROM "users"
> # INNER JOIN "posts" ON "posts"."author_id" = "users"."id"
> # WHERE (posts.published_at IS NOT NULL AND posts.published_at <=
> '2010-02-27 02:55:45.063181')
> # GROUP BY users.id
>
> This is taken
> from:http://edgerails.info/articles/what-s-new-in-edge-rails/2010/02/23/th...
That's actually something that Sequel doesn't have built in support
for, though it's a fairly simple if you don't mind a gross hack:
class Post < Sequel::Model
def_dataset_method(:published)
{exclude(:published_at=>nil).where{published_at < Time.now}.qualify}
end
class User < Sequel::Model
def_dataset_method(:published)
{group(:id).qualify.join(:posts,
:author_id=>:id).filter(Post.published.opts[:where])}
end
User.published.sql
# SELECT users.* FROM users
# INNER JOIN posts ON (posts.author_id = users.id)
# WHERE ((posts.published_at IS NOT NULL) AND (posts.published_at <
'2010-08-31 09:26:59.383300'))
# GROUP BY users.id
As to why Sequel doesn't support it by default, I think it's a bad
idea. What if you alias the posts table when joining? What if you
use "& Post.published" without joining to the posts table?
Honestly, the example they gave could be better, since (IMO) the
proper way to do things is this:
class Post < Sequel::Model
def_dataset_method(:published)
{exclude(:published_at=>nil).where{published_at < Time.now}}
end
class User < Sequel::Model
def_dataset_method(:published)
{group(:id).qualify.join(Post.published, :author_id=>:id)}
end
User.published.sql
# SELECT users.* FROM users
# INNER JOIN (
# SELECT * FROM posts
# WHERE ((published_at IS NOT NULL) AND
# (published_at < '2010-08-31 09:38:13.746317'))
# ) AS t1 ON (t1.author_id = users.id)
# GROUP BY users.id
or maybe even better, since you aren't returning anything from related
to posts:
class Post < Sequel::Model
def_dataset_method(:published)
{exclude(:published_at=>nil).where{published_at < Time.now}}
end
class User < Sequel::Model
def_dataset_method(:published)
{filter(:id=>Post.published.select(:author_id))}
end
User.published.sql
# SELECT * FROM users
# WHERE (id IN (
# SELECT author_id FROM posts
# WHERE ((published_at IS NOT NULL) AND
# (published_at < '2010-08-31 09:46:03.104467'))
# ))
Jeremy
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