Just curious : if there's no index on the column why don't you try to
add one ? That's probably why it takes a lot of time on the production
machine.
Jocelyn
Le 04/03/2009 18:26, Morten Primdahl a écrit :
Thanks for all the suggestions. The caching must be done somewhere else.
There is no index on the column and there are about 500.000 rows in the
table. A MySQL restart doesn't "flush" the cache in play, but a full
restart of my laptop does (OS X).
I may be chasing the wrong problem, but we have seen a query take a lot
of time on a production machine and have not been able to pin point why,
as the EXPLAIN looks good and the query is responsive enough when I run
it manually. I was just trying to reproduce that.
The below is after a full restart:
mysql> SET SESSION query_cache_type=off;
Query OK, 0 rows affected (0.00 sec)
mysql> select SQL_NO_CACHE count(*) from users where email = 'hello' AND
456 = 456;
+----------+
| count(*) |
+----------+
| 0 |
+----------+
1 row in set (28.80 sec)
mysql> RESET QUERY CACHE;
Query OK, 0 rows affected (0.00 sec)
mysql> select SQL_NO_CACHE count(*) from users where email = 'hello' AND
789 = 789;
+----------+
| count(*) |
+----------+
| 0 |
+----------+
1 row in set (0.44 sec)
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