I want to know how I can optimize it, preferably without changes in tables structure.
SELECT p.author_id member_id,
m.members_display_name member_name,
COUNT(p.pid) posts
FROM forum_topics t
STRAIGHT_JOIN forum_posts p
STRAIGHT_JOIN forum_members m
WHERE p.author_id != 0
AND p.author_id = m.member_id
AND p.new_topic = 0
AND t.forum_id = 120
AND t.tid = p.topic_id
GROUP BY p.author_id
ORDER BY posts DESC
LIMIT 1
Output of EXPLAIN is:
-------------------------------------------------------------------------------
EXPLAIN
SELECT p.author_id member_id,
m.members_display_name member_name,
COUNT(p.pid) posts
FROM forum_topics t
STRAIGHT_JOIN forum_posts p
STRAIGHT_JOIN forum_members m
WHERE p.author_id != 0
AND p.author_id = m.member_id
AND p.new_topic = 0
AND t.forum_id = 120
AND t.tid = p.topic_id
GROUP BY p.author_id
ORDER BY posts DESC
LIMIT 1\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: t
type: ref
possible_keys: PRIMARY,forum_id,last_post
key: forum_id
key_len: 2
ref: const
rows: 28070
Extra: Using temporary; Using filesort
*************************** 2. row ***************************
id: 1
select_type: SIMPLE
table: p
type: ref
possible_keys: author_id,topic_id
key: topic_id
key_len: 4
ref: forumwmo.t.tid
rows: 5
Extra: Using where
*************************** 3. row ***************************
id: 1
select_type: SIMPLE
table: m
type: eq_ref
possible_keys: PRIMARY
key: PRIMARY
key_len: 3
ref: forumwmo.p.author_id
rows: 1
Extra:
3 rows in set (0.00 sec)
Table structure is:
SHOW CREATE TABLE forum_members\G
*************************** 1. row ***************************
Table: forum_members
Create Table: CREATE TABLE `forum_members` (
`member_id` mediumint(8) NOT NULL AUTO_INCREMENT,
`name` varchar(32) NOT NULL DEFAULT '',
`member_group_id` smallint(3) NOT NULL DEFAULT '0',
`email` varchar(150) NOT NULL DEFAULT '',
`joined` int(10) NOT NULL DEFAULT '0',
`ip_address` varchar(16) NOT NULL DEFAULT '',
`posts` mediumint(7) DEFAULT '0',
`title` varchar(64) DEFAULT NULL,
`allow_admin_mails` tinyint(1) DEFAULT NULL,
`time_offset` varchar(10) DEFAULT NULL,
`hide_email` varchar(8) DEFAULT NULL,
`email_pm` tinyint(1) DEFAULT NULL,
`email_full` tinyint(1) DEFAULT NULL,
`skin` smallint(5) DEFAULT NULL,
`warn_level` int(10) DEFAULT NULL,
`warn_lastwarn` int(10) NOT NULL DEFAULT '0',
`language` varchar(32) DEFAULT NULL,
`last_post` int(10) DEFAULT NULL,
`restrict_post` varchar(100) NOT NULL DEFAULT '0',
`view_sigs` tinyint(1) DEFAULT '1',
`view_img` tinyint(1) DEFAULT '1',
`view_avs` tinyint(1) DEFAULT '1',
`view_pop` tinyint(1) DEFAULT '1',
`bday_day` int(2) DEFAULT NULL,
`bday_month` int(2) DEFAULT NULL,
`bday_year` int(4) DEFAULT NULL,
`msg_count_new` int(2) NOT NULL DEFAULT '0',
`msg_count_total` int(3) NOT NULL DEFAULT '0',
`msg_count_reset` int(1) NOT NULL DEFAULT '0',
`msg_show_notification` int(1) NOT NULL DEFAULT '0',
`misc` varchar(128) DEFAULT NULL,
`last_visit` int(10) DEFAULT '0',
`last_activity` int(10) DEFAULT '0',
`dst_in_use` tinyint(1) DEFAULT '0',
`view_prefs` varchar(64) DEFAULT '-1&-1',
`coppa_user` tinyint(1) DEFAULT '0',
`mod_posts` varchar(100) NOT NULL DEFAULT '0',
`auto_track` varchar(50) DEFAULT '0',
`org_perm_id` varchar(255) DEFAULT '',
`temp_ban` varchar(100) DEFAULT '0',
`sub_end` int(10) NOT NULL DEFAULT '0',
`no_sig_lims` tinyint(1) NOT NULL DEFAULT '0',
`login_anonymous` char(3) NOT NULL DEFAULT '0&0',
`ignored_users` text,
`mgroup_others` varchar(255) NOT NULL DEFAULT '',
`member_login_key` varchar(32) NOT NULL DEFAULT '',
`member_login_key_expire` int(10) NOT NULL DEFAULT '0',
`subs_pkg_chosen` smallint(3) NOT NULL DEFAULT '0',
`has_blog` tinyint(1) NOT NULL DEFAULT '0',
`members_auto_dst` tinyint(1) NOT NULL DEFAULT '1',
`members_cache` mediumtext,
`members_disable_pm` int(1) NOT NULL DEFAULT '0',
`members_display_name` varchar(255) NOT NULL DEFAULT '',
`members_seo_name` varchar(255) NOT NULL DEFAULT '',
`members_created_remote` tinyint(1) NOT NULL DEFAULT '0',
`members_editor_choice` char(3) NOT NULL DEFAULT 'std',
`members_profile_views` int(10) unsigned NOT NULL DEFAULT '0',
`members_l_display_name` varchar(255) NOT NULL DEFAULT '0',
`members_l_username` varchar(255) NOT NULL DEFAULT '0',
`failed_logins` text,
`failed_login_count` smallint(3) NOT NULL DEFAULT '0',
`has_gallery` int(1) DEFAULT '0',
`members_pass_hash` varchar(32) NOT NULL DEFAULT '',
`members_pass_salt` varchar(5) NOT NULL DEFAULT '',
`member_banned` tinyint(1) NOT NULL DEFAULT '0',
`identity_url` text,
`member_uploader` varchar(32) NOT NULL DEFAULT 'default',
`members_bitoptions` int(10) unsigned NOT NULL DEFAULT '0',
`fb_uid` bigint(20) NOT NULL DEFAULT '0',
`fb_emailhash` varchar(60) NOT NULL DEFAULT '',
`fb_emailallow` int(1) NOT NULL DEFAULT '0',
`fb_lastsync` int(10) NOT NULL DEFAULT '0',
`members_day_posts` varchar(32) NOT NULL DEFAULT '0,0',
`live_id` varchar(32) DEFAULT NULL,
PRIMARY KEY (`member_id`),
KEY `mgroup` (`member_group_id`),
KEY `bday_day` (`bday_day`),
KEY `bday_month` (`bday_month`),
KEY `members_l_display_name` (`members_l_display_name`),
KEY `members_l_username` (`members_l_username`),
KEY `member_banned` (`member_banned`),
KEY `members_bitoptions` (`members_bitoptions`),
KEY `ip_address` (`ip_address`)
) ENGINE=MyISAM AUTO_INCREMENT=101965 DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
-------------------------------------------------------------------------------
SHOW CREATE TABLE forum_posts\G
*************************** 1. row ***************************
Table: forum_posts
Create Table: CREATE TABLE `forum_posts` (
`append_edit` tinyint(1) DEFAULT '0',
`edit_time` int(10) DEFAULT NULL,
`pid` int(10) NOT NULL AUTO_INCREMENT,
`author_id` mediumint(8) NOT NULL DEFAULT '0',
`author_name` varchar(32) DEFAULT NULL,
`use_sig` tinyint(1) NOT NULL DEFAULT '0',
`use_emo` tinyint(1) NOT NULL DEFAULT '0',
`ip_address` varchar(16) NOT NULL DEFAULT '',
`post_date` int(10) DEFAULT NULL,
`icon_id` smallint(3) DEFAULT NULL,
`post` mediumtext,
`queued` tinyint(1) NOT NULL DEFAULT '0',
`topic_id` int(10) NOT NULL DEFAULT '0',
`post_title` varchar(255) DEFAULT NULL,
`new_topic` tinyint(1) DEFAULT '0',
`edit_name` varchar(255) DEFAULT NULL,
`post_parent` int(10) NOT NULL DEFAULT '0',
`post_key` varchar(32) NOT NULL DEFAULT '0',
`post_htmlstate` smallint(1) NOT NULL DEFAULT '0',
`post_edit_reason` varchar(255) NOT NULL DEFAULT '',
PRIMARY KEY (`pid`),
KEY `author_id` (`author_id`,`topic_id`),
KEY `post_date` (`post_date`),
KEY `topic_id` (`topic_id`,`queued`,`pid`,`post_date`),
KEY `post_key` (`post_key`),
KEY `ip_address` (`ip_address`)
) ENGINE=MyISAM AUTO_INCREMENT=988489 DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
-------------------------------------------------------------------------------
SHOW CREATE TABLE forum_topics\G
*************************** 1. row ***************************
Table: forum_topics
Create Table: CREATE TABLE `forum_topics` (
`tid` int(10) NOT NULL AUTO_INCREMENT,
`title` varchar(70) NOT NULL DEFAULT '',
`description` varchar(250) DEFAULT NULL,
`state` varchar(8) DEFAULT NULL,
`posts` int(10) DEFAULT NULL,
`starter_id` mediumint(8) NOT NULL DEFAULT '0',
`start_date` int(10) DEFAULT NULL,
`last_poster_id` mediumint(8) NOT NULL DEFAULT '0',
`last_post` int(10) DEFAULT NULL,
`icon_id` tinyint(2) DEFAULT NULL,
`starter_name` varchar(255) DEFAULT NULL,
`last_poster_name` varchar(255) DEFAULT NULL,
`poll_state` varchar(8) DEFAULT NULL,
`last_vote` int(10) DEFAULT NULL,
`views` int(10) DEFAULT '0',
`forum_id` smallint(5) NOT NULL DEFAULT '0',
`approved` tinyint(1) NOT NULL DEFAULT '0',
`author_mode` tinyint(1) DEFAULT NULL,
`pinned` tinyint(1) NOT NULL DEFAULT '0',
`moved_to` varchar(64) DEFAULT NULL,
`total_votes` int(5) NOT NULL DEFAULT '0',
`topic_hasattach` smallint(5) NOT NULL DEFAULT '0',
`topic_firstpost` int(10) NOT NULL DEFAULT '0',
`topic_queuedposts` int(10) NOT NULL DEFAULT '0',
`topic_rating_total` smallint(5) unsigned NOT NULL DEFAULT '0',
`topic_rating_hits` smallint(5) unsigned NOT NULL DEFAULT '0',
`topic_open_time` int(10) NOT NULL DEFAULT '0',
`topic_close_time` int(10) NOT NULL DEFAULT '0',
`title_seo` varchar(250) NOT NULL DEFAULT '',
`seo_last_name` varchar(255) NOT NULL DEFAULT '',
`seo_first_name` varchar(255) NOT NULL DEFAULT '',
PRIMARY KEY (`tid`),
KEY `topic_firstpost` (`topic_firstpost`),
KEY `forum_id` (`forum_id`,`pinned`,`approved`),
KEY `last_post` (`forum_id`,`pinned`,`last_post`),
KEY `starter_id` (`starter_id`,`forum_id`,`approved`),
KEY `last_post_sorting` (`last_post`,`forum_id`),
KEY `start_date` (`start_date`),
FULLTEXT KEY `title` (`title`)
) ENGINE=MyISAM AUTO_INCREMENT=227233 DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
Table properties are:
SHOW TABLE STATUS LIKE 'forum_members'\G
*************************** 1. row ***************************
Name: forum_members
Engine: MyISAM
Version: 10
Row_format: Dynamic
Rows: 64866
Avg_row_length: 257
Data_length: 16688164
Max_data_length: 281474976710655
Index_length: 6540288
Data_free: 0
Auto_increment: 101965
Create_time: 2009-12-02 05:45:59
Update_time: 2009-12-02 05:46:07
Check_time: 2009-12-02 05:49:23
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)
-------------------------------------------------------------------------------
SHOW TABLE STATUS LIKE 'forum_posts'\G
*************************** 1. row ***************************
Name: forum_posts
Engine: MyISAM
Version: 10
Row_format: Dynamic
Rows: 581777
Avg_row_length: 720
Data_length: 419170168
Max_data_length: 281474976710655
Index_length: 46439424
Data_free: 0
Auto_increment: 988489
Create_time: 2009-12-02 05:47:04
Update_time: 2009-12-02 05:48:13
Check_time: 2009-12-02 05:49:28
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)
-------------------------------------------------------------------------------
SHOW TABLE STATUS LIKE 'forum_topics'\G
*************************** 1. row ***************************
Name: forum_topics
Engine: MyISAM
Version: 10
Row_format: Dynamic
Rows: 117458
Avg_row_length: 144
Data_length: 17004836
Max_data_length: 281474976710655
Index_length: 14105600
Data_free: 0
Auto_increment: 227233
Create_time: 2009-12-02 05:48:38
Update_time: 2009-12-02 05:48:43
Check_time: 2009-12-02 05:49:28
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)
Other configuration details:
SHOW VARIABLES LIKE '%buffer%'\G
*************************** 1. row ***************************
Variable_name: bulk_insert_buffer_size
Value: 8388608
*************************** 2. row ***************************
Variable_name: innodb_buffer_pool_size
Value: 8388608
*************************** 3. row ***************************
Variable_name: innodb_log_buffer_size
Value: 1048576
*************************** 4. row ***************************
Variable_name: join_buffer_size
Value: 131072
*************************** 5. row ***************************
Variable_name: key_buffer_size
Value: 8384512
*************************** 6. row ***************************
Variable_name: myisam_sort_buffer_size
Value: 8388608
*************************** 7. row ***************************
Variable_name: net_buffer_length
Value: 16384
*************************** 8. row ***************************
Variable_name: pbxt_log_buffer_size
Value: 256K
*************************** 9. row ***************************
Variable_name: pbxt_transaction_buffer_size
Value: 1MB
*************************** 10. row ***************************
Variable_name: preload_buffer_size
Value: 32768
*************************** 11. row ***************************
Variable_name: read_buffer_size
Value: 131072
*************************** 12. row ***************************
Variable_name: read_rnd_buffer_size
Value: 262144
*************************** 13. row ***************************
Variable_name: sort_buffer_size
Value: 2097144
*************************** 14. row ***************************
Variable_name: sql_buffer_result
Value: OFF
14 rows in set (0.00 sec)
You might gain increased performance by moving some of your WHERE clause conditions up into your JOINs since this will cut down the result set as the query is executed e.g.
Although, the optimizer may be smart enough to do this for you. Also, although I don’t use MySQL, my understanding of the STRAIGH_JOIN is that it joins that tables in an explicit left to right order so it may make a difference if the tables are listed in size order from smallest to largest and vica versa.