On Fri, Feb 27, 2009 at 2:29 AM, Tim Starling <tstarling(a)wikimedia.org> wrote:
On thistle with DB=dewiki:
mysql> explain select * from recentchanges
left join tag_summary on ts_rc_id=rc_id
order by rc_timestamp desc limit 50\G
*************************** 1. row ***************************
table: recentchanges
type: ALL
possible_keys: NULL
key: NULL
key_len: NULL
ref: NULL
rows: 1179921
Extra: Using temporary; Using filesort
*************************** 2. row ***************************
table: tag_summary
type: ALL
possible_keys: ts_rc_id
key: NULL
key_len: NULL
ref: NULL
rows: 4
Extra:
2 rows in set (0.00 sec)
Almost two months later, but now that I have access to the toolsever
DB, here's some output from zedler on dewiki:
mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.1.33 |
+-----------+
1 row in set (0.00 sec)
mysql> explain select * from recentchanges left join tag_summary on
ts_rc_id=rc_id order by rc_timestamp desc limit 50\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: recentchanges
type: index
possible_keys: NULL
key: rc_timestamp
key_len: 16
ref: NULL
rows: 50
Extra:
*************************** 2. row ***************************
id: 1
select_type: SIMPLE
table: tag_summary
type: ref
possible_keys: ts_rc_id
key: ts_rc_id
key_len: 5
ref: dewiki.recentchanges.rc_id
rows: 1
Extra:
2 rows in set (0.00 sec)
So "MySQL 5.1" is a valid answer. (EXPLAIN even understands LIMIT now, yay!)