Separate the table name from the table subquery about active_record_union

[brianhempel]

From the example in your README:

current_user.posts.union(Post.published,true)

SELECT "posts".* FROM (
  SELECT "posts".* FROM "posts"  WHERE "posts"."user_id" = ?
  UNION
  SELECT "posts".* FROM "posts"  WHERE (published_at < '2014-07-19 16:04:21.918366')
) posts_union, posts

…you are selecting "posts".* from posts_union, posts, which if loaded into ActiveRecord would actually load every single post, not the union result. You would want to SELECT "posts_union".* to load the records from the union. However, if you SELECT "posts_union".*, then any .where() calls will filter "posts", which we don't want.

current_user.posts.union(Post.published,true).where(public: true)

SELECT "posts_union".* FROM (
  SELECT "posts".* FROM "posts"  WHERE "posts"."user_id" = ?
  UNION
  SELECT "posts".* FROM "posts"  WHERE (published_at < '2014-07-19 16:04:21.918366')
) posts_union, posts WHERE "posts"."public" = 't'

…we'd probably want WHERE "posts_union"."public" = 't' instead of WHERE "posts"."public" = 't'.

Maybe something like SELECT "posts".* FROM posts AS original_posts, (union stuff) posts

In any case, the whole thing is a CROSS JOIN which weirds me out. Why do you need a CROSS JOIN?

I'm not sure this is a problem that ActiveRecordUnion should support. Can you provide a full example of what kind of aggregation you are trying to do?