mysql follow and retweet-like functionality - mysql

Question

This is a bit challenging but fun question.
Consider having these tables
tweets
tweet_id | retweet_of_id | user_id
follow
user_id | followed_user_id
So we store each "retweet as a separate tweet" pointing to the original tweet's id (retweet_of_id). This is because I want to have comments under each one separately.
If something is not a retweet then retweet_of_id will be 0.
How do I retrieve the following using MySQL efficiently?
My own tweets
All the original tweets (from users that I follow)
And the first retweet (by a user I follow) of a tweet (from a user that I don't follow)
And that the result should a combination of both (in order) just like how twitter does it.
Please consider that there may be 1,000,000 tweets and we only need the most recent ones (e.g.: 10).
Here is an example (I'm user 1 and I follow user 2 & 3)
tweet_id | retweet_of_id | user_id
----------------------------------
1 0 4 <- EXCLUDE (I don't follow user 4)
2 0 2 <- INCLUDE (I follow user 2)
3 0 3 <- INCLUDE (I follow user 3)
4 1 2 <- INCLUDE (I follow user 2 & first RT)
5 1 3 <- EXCLUDE (I already have the first RT)
6 2 3 <- EXCLUDE (I already have the orignal)
7 0 1 <- INCLUDE (My own tweet)
So the final order should be these tweets: 7, 4, 3, 2 (starting with the most recent)

Answer 1

Here's how I solved it
(both of these assume that the tweets are ordered by their tweet_id ASC)
Solution 1 (correct, runs fast)
SELECT tweet_id,
FROM tweets
WHERE user = 1 OR user IN (2,3)
GROUP BY IF(retweet_of_id = 0, tweet_id, retweet_of_id)
ORDER BY tweet_id DESC
Solution 2 (gives correct results, but it's dog slow for 1,000,000 tweets)
SELECT p1.tweet_id FROM tweets p1
LEFT JOIN tweets p2
ON p2.user IN (2,3)
AND p1.tweet_id > p2.tweet_id
AND (p1.retweet_of_id = p2.tweet_id
OR p1.retweet_of_id AND p1.retweet_of_id = p2.retweet_of_id )
WHERE p2.tweet_id IS NULL
AND (p1.user = 1 OR p1.user IN (2,3))
ORDER BY p1.tweet_id DESC

Answer 2

all the original tweets (from users that I follow)
1 users that i follow:
select user_id from follow where followed_user_id= MyOwnID
2 all the original tweets:
select * from tweets where retweed_of_id=0
both combined:
select * from tweets where retweed_of_id=0 and
user_id in (select user_id from follow where followed_user_id= MyOwnID)
that should be it - or did i miss something?