MySQL Performance issue with large number of rows -


i developing site based on xenforo engine, , have problem in query fetches threads , joins post table , forum table information first post , forum thread belongs to. query looks like:

select thread . *
xf_thread thread
inner join xf_node node on (node.node_id = thread.node_id)
inner join xf_post post on (post.post_id = thread.first_post_id)
thread.node_id in ('295', '296', '297', '298', '299', '300', '301', '302', '256', '2575', '258', '259', '260', '253', '254', '255', '127', '163', '159', '144', '145', '146', '147', '148', '164', '165', '166', '167', '168', '169', '170', '162', '171', '173', '172', '128', '129', '130', '131', '132', '133', '134', '135', '136', '137', '138', '139', '140', '141', '142', '143', '151', '152', '153', '154', '155', '157', '156', '158', '161', '160', '149', '227', '232', '237', '233', '236', '234', '235', '238', '248', '240', '241', '242', '239', '246', '247', '243', '244', '245', '228', '229', '230', '231', '249', '250', '251', '174', '190', '195', '199', '193', '191', '197', '198', '192', '200', '204', '207', '205', '203', '206', '202', '208', '201', '187', '176', '177', '178', '189', '188', '180', '186', '184', '185', '182', '183', '181', '179', '209', '211', '217', '218', '219', '210', '212', '213', '214', '215', '216', '220', '222', '223', '224', '221', '225', '261', '291', '276', '272', '270', '265', '277', '267', '286', '292', '289', '274', '264', '287', '278', '282', '279', '281', '280', '283', '284', '285', '290', '275', '268', '263', '266', '294', '262', '293', '269', '273', '288', '271')
order thread.last_post_date desc
limit 10

explain results query are:

 id  select_type table   type    possible_keys   key key_len ref rows    1   simple  node    index   primary primary 4   null    199 using where; using index; using temporary; using filesort 1   simple  thread  ref node_id_last_post_date,node_id_sticky_last_post_date    node_id_last_post_date  4   node.node_id    221   1   simple  post    eq_ref  primary primary 4   thread.first_post_id    1   using index

query takes 9+ seconds execute.

removing joining of xf_node table, runs query in 0.01 seconds. explain looks 

id select_type table   type    possible_keys   key key_len ref rows    1   simple  thread  index   node_id_last_post_date,node_id_sticky_last_post_da...   last_post_date  4   null    69970   using 1   simple  post    eq_ref  primary primary 4   thread.first_post_id    1   using index

removing joining of xf_post table runs query in 0.01 seconds, explain looks 

id select_type table   type    possible_keys   key key_len ref rows    1   simple  thread  index   node_id_last_post_date,node_id_sticky_last_post_da...   last_post_date  4   null    70840   using 1   simple  node    eq_ref  primary primary 4   thread.node_id  1   using index

so, problem exists when both tables joined, joins seem correct , work separately.

number of rows in tables - xf_thread: 71,855, xf_node: 178, xf_post: 2,977,326

my assumption when both tables joined mysql starts use incorrect indexes, , maybe forcing index solve problem?

your , suggestions find way resolve problem highly appreciated.

edit: here create table statements tables involved

xf_node

create table `xf_node` (     `node_id` int(10) unsigned not null auto_increment,     `title` varchar(50) not null,     `description` text not null,     `node_name` varchar(50) default null comment 'unique column used string id node types',     `node_type_id` varbinary(25) not null,     `parent_node_id` int(10) unsigned not null default '0',     `display_order` int(10) unsigned not null default '1',     `display_in_list` tinyint(3) unsigned not null default '1' comment 'if 0, hidden node list. still counts lft/rgt.',     `lft` int(10) unsigned not null default '0' comment 'nested set info ''left'' value',     `rgt` int(10) unsigned not null default '0' comment 'nested set info ''right'' value',     `depth` int(10) unsigned not null default '0' comment 'depth = 0: no parent',     `style_id` int(10) unsigned not null default '0' comment 'style override specific node',     `effective_style_id` int(10) unsigned not null default '0' comment 'style override; pushed down tree',     primary key  (`node_id`),     unique key `node_name_unique` (`node_name`,`node_type_id`),     key `parent_node_id` (`parent_node_id`),     key `display_order` (`display_order`),     key `display_in_list` (`display_in_list`,`lft`),     key `lft` (`lft`)   ) engine=innodb  default charset=utf8 auto_increment=304 ;

xf_post

create table `xf_post` (     `post_id` int(10) unsigned not null auto_increment,     `thread_id` int(10) unsigned not null,     `user_id` int(10) unsigned not null,     `username` varchar(50) not null,     `post_date` int(10) unsigned not null,     `message` mediumtext not null,     `ip_id` int(10) unsigned not null default '0',     `message_state` enum('visible','moderated','deleted') not null default 'visible',     `attach_count` smallint(5) unsigned not null default '0',     `position` int(10) unsigned not null,     `likes` int(10) unsigned not null default '0',     `like_users` blob not null,     `warning_id` int(10) unsigned not null default '0',     `warning_message` varchar(255) not null default '',     primary key  (`post_id`),     key `thread_id_post_date` (`thread_id`,`post_date`),     key `thread_id_position` (`thread_id`,`position`),     key `user_id` (`user_id`)   ) engine=innodb  default charset=utf8 auto_increment=3123657 ;

xf_thread

create table `xf_thread` (     `thread_id` int(10) unsigned not null auto_increment,     `node_id` int(10) unsigned not null,     `title` varchar(150) not null,     `reply_count` int(10) unsigned not null default '0',     `view_count` int(10) unsigned not null default '0',     `user_id` int(10) unsigned not null,     `username` varchar(50) not null,     `post_date` int(10) unsigned not null,     `sticky` tinyint(3) unsigned not null default '0',     `discussion_state` enum('visible','moderated','deleted') not null default 'visible',     `discussion_open` tinyint(3) unsigned not null default '1',     `discussion_type` varchar(25) not null default '',     `first_post_id` int(10) unsigned not null,     `first_post_likes` int(10) unsigned not null default '0',     `last_post_date` int(10) unsigned not null,     `last_post_id` int(10) unsigned not null,     `last_post_user_id` int(10) unsigned not null,     `last_post_username` varchar(50) not null,     `prefix_id` int(10) unsigned not null default '0',     primary key  (`thread_id`),     key `node_id_last_post_date` (`node_id`,`last_post_date`),     key `node_id_sticky_last_post_date` (`node_id`,`sticky`,`last_post_date`),     key `last_post_date` (`last_post_date`)   ) engine=innodb  default charset=utf8 auto_increment=76301 ;

thank you.

sometimes order clause in mysql use temp table sort results. large data can take lot of time. avoid using "order desc" , sort data outside mysql.


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