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Fix for massively slow friends timeline query due to indexing bug introduced with repeats.

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Sorting on notice.id when our primary selector was notice_inbox.user_id caused a filesort and table scan of the notice table.
Switchng to notice_inbox's notice_id means we can use our index, and everything comes right up.

Before:
mysql> explain SELECT notice.id AS id FROM notice JOIN notice_inbox ON notice.id = notice_inbox.notice_id WHERE notice_inbox.user_id = 18574 AND notice.repeat_of IS NULL ORDER BY notice.id DESC LIMIT 61 OFFSET 0;
+----+-------------+--------------+--------+------------------------------------+---------+---------+-------------------------------+--------+----------------------------------------------+
| id | select_type | table        | type   | possible_keys                      | key     | key_len | ref                           | rows   | Extra                                        |
+----+-------------+--------------+--------+------------------------------------+---------+---------+-------------------------------+--------+----------------------------------------------+
|  1 | SIMPLE      | notice_inbox | ref    | PRIMARY,notice_inbox_notice_id_idx | PRIMARY | 4       | const                         | 102600 | Using index; Using temporary; Using filesort |
|  1 | SIMPLE      | notice       | eq_ref | PRIMARY                            | PRIMARY | 4       | stoica.notice_inbox.notice_id |      1 | Using index                                  |
+----+-------------+--------------+--------+------------------------------------+---------+---------+-------------------------------+--------+----------------------------------------------+

After:
mysql> explain SELECT notice.id AS id FROM notice JOIN notice_inbox ON notice.id = notice_inbox.notice_id WHERE notice_inbox.user_id = 18574 AND notice.repeat_of IS NULL ORDER BY notice_id DESC LIMIT 61 OFFSET 0;
+----+-------------+--------------+--------+------------------------------------+---------+---------+-------------------------------+--------+--------------------------+
| id | select_type | table        | type   | possible_keys                      | key     | key_len | ref                           | rows   | Extra                    |
+----+-------------+--------------+--------+------------------------------------+---------+---------+-------------------------------+--------+--------------------------+
|  1 | SIMPLE      | notice_inbox | ref    | PRIMARY,notice_inbox_notice_id_idx | PRIMARY | 4       | const                         | 102816 | Using where; Using index |
|  1 | SIMPLE      | notice       | eq_ref | PRIMARY,notice_repeatof_idx        | PRIMARY | 4       | stoica.notice_inbox.notice_id |      1 | Using where              |
+----+-------------+--------------+--------+------------------------------------+---------+---------+-------------------------------+--------+--------------------------+
This commit is contained in:
Brion Vibber 2009-12-22 20:18:27 -08:00
parent f6bf952980
commit fa0fbd0118
1 changed files with 1 additions and 1 deletions
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2
classes/User.php
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@ -543,7 +543,7 @@ class User extends Memcached_DataObject
// NOTE: we sort by fave time, not by notice time!
$qry .= 'ORDER BY notice.id DESC ';
$qry .= 'ORDER BY notice_id DESC ';
if (!is_null($offset)) {
$qry .= "LIMIT $limit OFFSET $offset";