https://bugzilla.wikimedia.org/show_bug.cgi?id=14971
--- Comment #19 from Aryeh Gregor <simetrical+wikib...@gmail.com> 2009-01-21
17:31:23 UTC ---
EXPLAINs on enwikinews_p from toolserver:
mysql> EXPLAIN SELECT page_namespace, page_title, c1.cl_timestamp FROM `page`
INNER JOIN `categorylinks` AS c1 ON page_id = c1.cl_from AND c1.cl_to='Test'
WHERE 1=1 AND page_is_redirect = 0 ORDER BY c1.cl_timestamp DESC;
+----+-------------+---------------+--------+---------------------------------+--------------+---------+----------------------------------+------+--------------------------+
| id | select_type | table | type | possible_keys |
key | key_len | ref | rows | Extra
|
+----+-------------+---------------+--------+---------------------------------+--------------+---------+----------------------------------+------+--------------------------+
| 1 | SIMPLE | categorylinks | ref | cl_from,cl_timestamp,cl_sortkey |
cl_timestamp | 257 | const | 1 | Using where;
Using index |
| 1 | SIMPLE | page | eq_ref | PRIMARY |
PRIMARY | 4 | enwikinews.categorylinks.cl_from | 1 | Using where
|
+----+-------------+---------------+--------+---------------------------------+--------------+---------+----------------------------------+------+--------------------------+
2 rows in set (0.03 sec)
mysql> EXPLAIN SELECT page_namespace, page_title, c1.cl_timestamp FROM `page`
INNER JOIN `categorylinks` AS c1 ON page_id = c1.cl_from AND c1.cl_to='Test'
WHERE 1=1 AND page_is_redirect = 0 ORDER BY page_touched DESC;
+----+-------------+---------------+--------+---------------------------------+--------------+---------+----------------------------------+------+-----------------------------------------------------------+
| id | select_type | table | type | possible_keys |
key | key_len | ref | rows | Extra
|
+----+-------------+---------------+--------+---------------------------------+--------------+---------+----------------------------------+------+-----------------------------------------------------------+
| 1 | SIMPLE | categorylinks | ref | cl_from,cl_timestamp,cl_sortkey |
cl_timestamp | 257 | const | 1 | Using where;
Using index; Using temporary; Using filesort |
| 1 | SIMPLE | page | eq_ref | PRIMARY |
PRIMARY | 4 | enwikinews.categorylinks.cl_from | 1 | Using where
|
+----+-------------+---------------+--------+---------------------------------+--------------+---------+----------------------------------+------+-----------------------------------------------------------+
2 rows in set (0.00 sec)
mysql> EXPLAIN SELECT page_namespace, page_title, c1.cl_timestamp FROM `page`
INNER JOIN `categorylinks` AS c1 ON page_id = c1.cl_from AND c1.cl_to='Test'
WHERE 1=1 AND page_is_redirect = 0 ORDER BY page_title DESC;
+----+-------------+---------------+--------+---------------------------------+--------------+---------+----------------------------------+------+-----------------------------------------------------------+
| id | select_type | table | type | possible_keys |
key | key_len | ref | rows | Extra
|
+----+-------------+---------------+--------+---------------------------------+--------------+---------+----------------------------------+------+-----------------------------------------------------------+
| 1 | SIMPLE | categorylinks | ref | cl_from,cl_timestamp,cl_sortkey |
cl_timestamp | 257 | const | 1 | Using where;
Using index; Using temporary; Using filesort |
| 1 | SIMPLE | page | eq_ref | PRIMARY |
PRIMARY | 4 | enwikinews.categorylinks.cl_from | 1 | Using where
|
+----+-------------+---------------+--------+---------------------------------+--------------+---------+----------------------------------+------+-----------------------------------------------------------+
2 rows in set (0.00 sec)
If the middle query is actually being run, the last one shouldn't be any worse,
I suppose. But it still looks bad. I'm very reluctant to commit this,
especially since I've never used the extension and am not familiar with its
code. Sorry.
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