Before I post it as a bug, perhaps someone can explain why
this query is not optimized to use the index (it has to examine all 287k rows).
mysql> explain SELECT MAX(changed) FROM archived_stats where changed>0;
+----------------+-------+---------------+---------+---------+------+---------+--------------------------+
| table | type | possible_keys | key | key_len | ref | rows | Extra
|
+----------------+-------+---------------+---------+---------+------+---------+--------------------------+
| archived_stats | range | changed | changed | 4 | NULL | 2878820 | Using
where; Using index |
+----------------+-------+---------------+---------+---------+------+---------+--------------------------+
whereas this query is optimized:
mysql> explain SELECT MAX(changed) FROM archived_stats;
+------------------------------+
| Comment |
+------------------------------+
| Select tables optimized away |
+------------------------------+
The table in question:
mysql> describe archived_stats;
+--------------+---------------+------+-----+---------------------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+---------------+------+-----+---------------------+-------+
| number | char(32) | | MUL | | |
| bad_login | int(11) | | | 0 | |
| good_login | int(11) | | | 0 | |
| last_login | timestamp(14) | YES | | NULL | |
| batch_flow | int(11) | | | 0 | |
| upload_image | int(11) | | | 0 | |
| page_proof | int(11) | | | 0 | |
| process_form | int(11) | | | 0 | |
| changed | timestamp(14) | YES | MUL | 00000000000000 | |
| sync_date | datetime | YES | | 0000-00-00 00:00:00 | |
+--------------+---------------+------+-----+---------------------+-------+
10 rows in set (0.03 sec)
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