Find last n entries ordered by association - postgresql

Question

I have a table Stories and a table Post. Each Story contains multiple Posts (Story.hasMany(models.Post);, Post.belongsTo(models.Story);)
What I'm trying to achieve is to list the first 10 Stories ordered by Posts.createdAt. So it might be possible that the first entry is the oldest Story but with a very new Post.
What I'm trying right now is the following:
var options = {
limit: 10,
offset: 0,
include: [{
model: models.sequelize.model('Post'),
attributes: ['id', 'createdAt'],
required: true
}],
order: [
[models.sequelize.model('Post'), 'createdAt', 'DESC'],
['createdAt', 'DESC']
],
attributes: ['id', 'title', 'createdAt']
};
Story.findAll(options)...
Which gives me this SQL query:
SELECT "Story".*, "Posts"."id" AS "Posts.id", "Posts"."createdAt" AS "Posts.createdAt"
FROM (SELECT "Story"."id", "Story"."title", "Story"."createdAt"
FROM "Stories" AS "Story"
WHERE ( SELECT "StoryId"
FROM "Posts" AS "Post"
WHERE ("Post"."StoryId" = "Story"."id") LIMIT 1 ) IS NOT NULL
ORDER BY "Story"."createdAt" DESC LIMIT 10) AS "Story"
INNER JOIN "Posts" AS "Posts" ON "Story"."id" = "Posts"."StoryId"
ORDER BY "Posts"."createdAt" DESC, "Story"."createdAt" DESC;
The problem here is that if the 11th entry has a very new post it is not displayed in the top 10 list.
How can I get a limited list of stories ordered by Posts.createdAt?

Answer 1

Why are you using two nested subselects? That's ineffective, might produce expensive nested loops, and still does not return what you are looking for.
As a start, you can cross-join Stories and Posts, order by the creation timestamp from Posts. But this still might scan the entire table.
Have a look at this presentation:
http://www.slideshare.net/MarkusWinand/p2d2-pagination-done-the-postgresql-way
But I have no idea, how you can bring that into your model :-(