On Thu, Aug 7, 2014 at 11:57 AM, Paul Jungwirth <pj@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Or another idea, add a column that is the path of the parent:I don't think this will work. The problem is you need the full path to
keep the children with their parents, but you also need the score. If
you make the path an array of (-votes, id) tuples (perhaps flattened
for simplicity), then you get the correct ordering. That way at every
stage you are sorting by votes, but still keeping children with their
parents:
comments=> WITH RECURSIVE cte (id, message, author, path, parent_id,
depth, votes) AS (
SELECT id,
message,
author,
array[-votes,id] AS path,
parent_id,
1 AS depth, votes
FROM comments
WHERE parent_id IS NULL
UNION ALL
SELECT comments.id,
comments.message,
comments.author,
cte.path || -comments.votes || comments.id,
comments.parent_id,
cte.depth + 1 AS depth, comments.votes
FROM comments
JOIN cte ON comments.parent_id = cte.id
)
SELECT id, message, author, path, depth, votes FROM cte
ORDER BY path;
id | message | author | path | depth | votes
----+-----------------------------+--------+-------------------+-------+-------
5 | Very interesting post! | thedz | {-3,5} | 1 | 3
8 | Fo sho, Yall | Mac | {-3,5,-12,8} | 2 | 12
7 | Agreed | G | {-3,5,-5,7} | 2 | 5
6 | You sir, are wrong | Chris | {-3,5,-3,6} | 2 | 3
1 | This thread is really cool! | David | {-1,1} | 1 | 1
3 | I agree David! | Daniel | {-1,1,-4,3} | 2 | 4
2 | Ya David, we love it! | Jason | {-1,1,-3,2} | 2 | 3
4 | gift Jason | Anton | {-1,1,-3,2,-15,4} | 3 | 15
(8 rows)
Time: 0.966 ms
This is outstanding, Paul. I'm still checking things over, but it looks like this is going to work. It looks like I was really close, but didn't think to go negative, and I had one of my arrays flip-flopped from what you've got. I made those two changes and it would appear that this is perfect.
Much appreciated, I would have been beating my head against this for a lot longer without the help!
