do you have an index defined on users.username ?
----- Original Message -----
From: "David Wolf" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Sunday, October 28, 2001 4:26 PM
Subject: Optimizing query (2nd attempt)
> I have a query as follows:
>
> SELECT log.entity, log.action,
> LEFT(users.username,10) AS username,
> LEFT(boards.title,15) AS Board,
> LEFT(topics.subject,22) as Subject,
> log.postid, log.extraid,
> LEFT(from_unixtime(log.logtime),19) AS time, log.ip
> FROM log LEFT JOIN users ON log.userid = users.id
> LEFT JOIN boards ON log.boardid=boards.id
> LEFT JOIN topics ON log.topicid = topics.id
> WHERE log.logTime > UNIX_TIMESTAMP("2000-10-26 23:00:00")
> AND users.username="testuser";
>
> When I run an 'explain' on it, I get:
>
>
+--------+--------+---------------+---------+---------+-------------+-------
> --+------------+
> | table | type | possible_keys | key | key_len | ref | rows
> | Extra |
>
+--------+--------+---------------+---------+---------+-------------+-------
> --+------------+
> | log | ALL | time | NULL | NULL | NULL |
> 1192384 | where used |
> | users | eq_ref | PRIMARY | PRIMARY | 4 | log.userId |
> 1 | where used |
> | boards | eq_ref | PRIMARY | PRIMARY | 4 | log.boardId |
> 1 | |
> | topics | eq_ref | PRIMARY | PRIMARY | 4 | log.topicId |
> 1 | |
>
+--------+--------+---------------+---------+---------+-------------+-------
> --+------------+
> 4 rows in set (0.01 sec)
>
> Now.. If I exclude the 'users.username="testuser"' and substitute it for
the
> userid that I got in a previous query (i.e. userid=2) so that the query
> becomes:
>
> SELECT log.entity, log.action,
> LEFT(users.username,10) AS username,
> LEFT(boards.title,15) AS Board,
> LEFT(topics.subject,22) as Subject,
> log.postid, log.extraid,
> LEFT(from_unixtime(log.logtime),19) AS time, log.ip
> FROM log LEFT JOIN users ON log.userid = users.id
> LEFT JOIN boards ON log.boardid=boards.id
> LEFT JOIN topics ON log.topicid = topics.id
> WHERE log.logTime > UNIX_TIMESTAMP("2000-10-26 23:00:00")
> AND log.userid=2;
>
>
> and run an explain, I get...
>
>
+--------+--------+---------------+---------+---------+-------------+-------
> +------------+
> | table | type | possible_keys | key | key_len | ref | rows
> | Extra |
>
+--------+--------+---------------+---------+---------+-------------+-------
> +------------+
> | log | ref | time,userid | userid | 4 | const |
27198
> | where used |
> | users | eq_ref | PRIMARY | PRIMARY | 4 | log.userId |
1
> | |
> | boards | eq_ref | PRIMARY | PRIMARY | 4 | log.boardId |
1
> | |
> | topics | eq_ref | PRIMARY | PRIMARY | 4 | log.topicId |
1
> | |
>
+--------+--------+---------------+---------+---------+-------------+-------
> +------------+
> 4 rows in set (0.00 sec)
>
> Big difference from 1.19million rows to 27198 rows... My question is this.
> How can I optimize the query with the left joins so that the optimizer
will
> first grab the userid from the username and then use the userid index on
log
> to return the results fast?
>
> Thanks in advance,
>
> David
>
>
>
>
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