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authorBrion Vibber <brion@pobox.com>2009-12-22 20:18:27 -0800
committerBrion Vibber <brion@pobox.com>2009-12-22 20:30:41 -0800
commitfa0fbd011812e9df52c9e5684d4cf953c6f75d8e (patch)
treea1d7c800f68b5fd820b6f21c25eb1273ce135ab3 /actions
parentf6bf9529805cd58fdd1671dd9b133bde05e8ae87 (diff)
Fix for massively slow friends timeline query due to indexing bug introduced with repeats.
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 | +----+-------------+--------------+--------+------------------------------------+---------+---------+-------------------------------+--------+--------------------------+
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