I use django on webfaction, and I've got a "MySql query taking too long" message,
the sql is
SELECT (1) AS `a` FROM `main_userprofile` WHERE `main_userprofile`.`id` = 98
This is a rather simple sql, why the query taken too long?
here it is the 'create table':
main_userprofile | CREATE TABLE `main_userprofile` (
`id` int(11) NOT NULL auto_increment,
`user_id` int(11) NOT NULL,
`sex` smallint(6) NOT NULL,
`active_number` varchar(64) NOT NULL,
`phone_number` varchar(32) NOT NULL,
`work_number` varchar(32) NOT NULL,
...
...
PRIMARY KEY (`id`),
UNIQUE KEY `user_id` (`user_id`)
) ENGINE=MyISAM AUTO_INCREMENT=1652 DEFAULT CHARSET=utf8 |
the id is the primary key
the explain:
explain SELECT (1) AS `a` FROM `main_userprofile` WHERE `main_userprofile`.`id` = 98;
+----+-------------+------------------+-------+---------------+---------+---------+-------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------------+-------+---------------+---------+---------+-------+------+-------------+
| 1 | SIMPLE | main_userprofile | const | PRIMARY | PRIMARY | 4 | const | 1 | Using index |
+----+-------------+------------------+-------+---------------+---------+---------+-------+------+-------------+
Seems like id is not indexed, isn't it. Is id the primary key of your table? Could you post the result of SHOW CREATE TABLE main_userprofile;?
Related
I have a query like
SELECT `table1`.*
FROM `table1`
WHERE `table1`.`table2_id` IN (1,2,6,12,53,666)
and it works more than 20 seconds
Explain looks like:
+----+-------------+--------------------------+------------+-------+-------------------------------------------------------------------------------+----------------------------------+---------+------+-------+----------+-----------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+--------------------------+------------+-------+-------------------------------------------------------------------------------+----------------------------------+---------+------+-------+----------+-----------------------+
| 1 | SIMPLE | table1 | NULL | range | table2_id | table2_id | 4 | NULL | 74778 | 100.00 | Using index condition |
+----+-------------+--------------------------+------------+-------+-------------------------------------------------------------------------------+----------------------------------+---------+------+-------+----------+-----------------------+
Table looks like
CREATE TABLE `table1` (
`id` bigint(20) NOT NULL AUTO_INCREMENT,
`table2_id` int(11) NOT NULL,
`table3_id` int(11) NOT NULL,
`field1` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`field2` int(11) NOT NULL DEFAULT '0',
`created_at` datetime NOT NULL,
`updated_at` datetime NOT NULL,
`field3` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `name_of_index_id` (`table3_id`),
KEY `other_name_of_index` (`field2`),
KEY `table2_id` (`table2_id`)
) ENGINE=InnoDB AUTO_INCREMENT=86623178 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
You can use index to fetch the result quickly. But, Indexing will take more space to generate and store in the database. So, if you are fine to utilize speed compare to space, Indexing will be used with following SQL statement.
ALTER TABLE `table1` ADD INDEX(`table2_id`);
I was migrating from my old MariaDB 10.0 database to new Google Cloud Sql with Mysql 5.7 with mysqldump method. After migrating, i got some very slow query regarding with WHERE EXISTS statement.
I tried to EXPLAIN my query on both my old DB and new DB and it explained different result. Since it using dump, i am assuming that no changes with the table indexes. This is the query that i wanted to run
SELECT * FROM detitem
where exists (select 1 from detlayanan
where detitem.iddetlayanan = detlayanan.id
and detlayanan.layanan_idlayanan='LYN15176176101503')
the EXPLAIN from old DB
+------+-------------+------------+------+------------------------------------+----------------------------+---------+--------------------------------+-------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+------+-------------+------------+------+------------------------------------+----------------------------+---------+--------------------------------+-------+--------------------------+
| 1 | PRIMARY | detlayanan | ref | PRIMARY,fk_detlayanan_layanan1_idx | fk_detlayanan_layanan1_idx | 22 | const | 11030 | Using where; Using index |
| 1 | PRIMARY | detitem | ref | FK_detitem_detlayanan | FK_detitem_detlayanan | 52 | citridia_sinadme.detlayanan.id | 1 | |
+------+-------------+------------+------+------------------------------------+----------------------------+---------+--------------------------------+-------+--------------------------+
and the EXPLAIN from new DB
+----+--------------------+------------+------------+--------+------------------------------------+---------+---------+---------------------------------------+---------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+--------------------+------------+------------+--------+------------------------------------+---------+---------+---------------------------------------+---------+----------+-------------+
| 1 | PRIMARY | detitem | NULL | ALL | NULL | NULL | NULL | NULL | 2079094 | 100.00 | Using where |
| 2 | DEPENDENT SUBQUERY | detlayanan | NULL | eq_ref | PRIMARY,fk_detlayanan_layanan1_idx | PRIMARY | 52 | citridia_sinadme.detitem.iddetlayanan | 1 | 5.00 | Using where |
+----+--------------------+------------+------------+--------+------------------------------------+---------+---------+---------------------------------------+---------+----------+-------------+
The new one is doing Full-table scan even there is index exist. Am i missing something here?
Here is the "detlayanan" table
CREATE TABLE `detlayanan` (
`transaksi_idtransaksi` varchar(40) NOT NULL,
`layanan_idlayanan` varchar(20) NOT NULL,
`nama_layanan` varchar(255) DEFAULT NULL,
`jumlah_beli` float DEFAULT NULL,
`id` varchar(50) NOT NULL,
`harga` decimal(20,2) DEFAULT '0.00',
`hargatotal` decimal(20,2) DEFAULT '0.00',
`luas_p` double(255,2) DEFAULT '0.00',
`luas_l` double(255,2) DEFAULT '0.00',
`luas_q` double(255,2) DEFAULT '0.00',
`keterangan` varchar(255) DEFAULT '',
`iddeposit` varchar(255) DEFAULT NULL,
`posisi` tinyint(4) DEFAULT '1',
`idworkshop` varchar(60) DEFAULT NULL,
`is_wsot` tinyint(4) DEFAULT '0',
`created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00' ON UPDATE CURRENT_TIMESTAMP,
`total_bersih` varchar(20) DEFAULT '0',
`total_min_order` decimal(20,2) DEFAULT '0.00',
`kondisi_barang` text,
PRIMARY KEY (`id`),
KEY `fk_detlayanan_layanan1_idx` (`layanan_idlayanan`),
KEY `fk_detlayanan_deposit` (`iddeposit`),
KEY `transaksi_idtransaksi` (`transaksi_idtransaksi`),
CONSTRAINT `detlayanan_ibfk_1` FOREIGN KEY (`transaksi_idtransaksi`) REFERENCES `transaksi` (`idtransaksi`),
CONSTRAINT `fk_detlayanan_layanan1` FOREIGN KEY (`layanan_idlayanan`) REFERENCES `layanan` (`idlayanan`) ON DELETE NO ACTION ON UPDATE NO ACTION
)
And here is the "detitem" table
CREATE TABLE `detitem` (
`item_iditem` varchar(20) NOT NULL,
`layanan_idlayanan` varchar(255) NOT NULL,
`jumlah_item` int(255) DEFAULT NULL,
`transaksi_idtransaksi` varchar(255) NOT NULL,
`id` varchar(50) NOT NULL,
`iddetlayanan` varchar(50) NOT NULL,
`created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00' ON UPDATE CURRENT_TIMESTAMP,
`hapus` tinyint(4) DEFAULT '0',
PRIMARY KEY (`id`),
KEY `FK_detitem_item` (`item_iditem`),
KEY `FK_detitem_layanan` (`layanan_idlayanan`),
KEY `FK_detitem_transaksi` (`transaksi_idtransaksi`),
KEY `FK_detitem_detlayanan` (`iddetlayanan`),
CONSTRAINT `FK_detitem_detlayanan` FOREIGN KEY (`iddetlayanan`) REFERENCES `detlayanan` (`id`),
CONSTRAINT `FK_detitem_item` FOREIGN KEY (`item_iditem`) REFERENCES `item` (`iditem`),
CONSTRAINT `FK_detitem_layanan` FOREIGN KEY (`layanan_idlayanan`) REFERENCES `layanan` (`idlayanan`),
CONSTRAINT `FK_detitem_transaksi` FOREIGN KEY (`transaksi_idtransaksi`) REFERENCES `transaksi` (`idtransaksi`)
)
I expect the "rows" on explain stay small, in the old DB, "rows" stays at very low even in another table. but in the new DB it can shows up to million.
UPDATE
After some research, actually i must explicitly add some indexed column in the where statement to accompany EXISTS statement. so the query would be like this
SELECT * FROM detitem WHERE
<indexed column> in (<some id's>)
AND EXISTS ( SELECT 1 FROM detlayanan WHERE detitem.iddetlayanan =
detlayanan.id AND detlayanan.layanan_idlayanan = 'LYN15176176101503' )
apparently MySQL doing full scan on detitem table to check the subquery values is exists or not, when some indexed column are declared, sql does not need to did that. Also this case were found in MySQL.
some references:
https://mariadb.com/kb/en/library/exists-to-in-optimization/
This looks like a case where MariaDB's Optimizer is a step or two ahead of MySQL's.
See if this works well:
SELECT i.*
FROM ( SELECT id
FROM detlayanan
WHERE layanan_idlayanan = 'LYN15176176101503'
) AS x
JOIN detitem AS i ON x.id = i.iddetlayanan
I think it will work well in both servers.
Simpler yet:
SELECT i.*
FROM detlayanan AS lay
JOIN detitem AS i ON lay.id = i.iddetlayanan
WHERE lay.layanan_idlayanan = 'LYN15176176101503'
Please refer the table strcuture below.
CREATE TABLE `oarc` (
`ID` bigint(20) NOT NULL AUTO_INCREMENT,
`zID` int(11) NOT NULL,
`cID` int(11) NOT NULL,
`bID` int(11) NOT NULL,
`rtype` char(1) COLLATE utf8_unicode_ci NOT NULL,
`created` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
PRIMARY KEY (`ID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1821039 ;
Other than the PRIMARY KEY, I have not set any index on this, and when I run the following query
select COUNT(oarc.ID) as total
from `oarc` where`oarc`.`rtype` = 'v'
group
by `oarc`.`zID`
I am getting the result in less than 1 second. But if I add index to zID it is taking more than 5 seconds.
Please see below explain result :
id | select_type | table | type | possible_keys | key | key_len | ref | row | Extra
--------------------------------------------------------------------------------------------------------
1 | SIMPLE | oarc | index | NULL | zone_ID | 4 | NULL | 1909387 | Using where
Currently the table have more than 1821039 records in it and it will increase on a hourly basis. What are the things I need to do in order to reduce the query execution time. I am expecting only something at the table and query level, nothing on my.cnf or server side because I can not do anything there.
Thanks in advance.
Is this better?
CREATE TABLE `oarc` (
`ID` bigint(20) NOT NULL AUTO_INCREMENT,
`zID` int(11) NOT NULL,
`cID` int(11) NOT NULL,
`bID` int(11) NOT NULL,
`rtype` char(1) COLLATE utf8_unicode_ci NOT NULL,
`created` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
PRIMARY KEY (`ID`),
KEY(rtype,zid)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1821039 ;
explain
select COUNT(oarc.ID) as total
from `oarc` where`oarc`.`rtype` = 'v'
group
by `oarc`.`zID`
+----+-------------+-------+------+---------------+-------+---------+-------+------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+------+---------------+-------+---------+-------+------+--------------------------+
| 1 | SIMPLE | oarc | ref | rtype | rtype | 3 | const | 1 | Using where; Using index |
+----+-------------+-------+------+---------------+-------+---------+-------+------+--------------------------+
i have one MySQL issue. I have to optimize some queries on my website. One of them i have already done, but there are still some which i cannot resolve without your help.
I have a table called "news":
CREATE TABLE IF NOT EXISTS `news` (
`id` int(10) NOT NULL auto_increment,
`edited` smallint(1) NOT NULL default '0',
`site` varchar(30) default NULL,
`foreign_id` varchar(25) default NULL,
`title` varchar(255) NOT NULL,
`text` text NOT NULL,
`image` varchar(255) default NULL,
`horizontal` smallint(1) NOT NULL,
`image_author` varchar(255) default NULL,
`text_author` varchar(255) default NULL,
`lang` varchar(3) NOT NULL,
`link` varchar(255) NOT NULL,
`date` date NOT NULL,
`redirect` smallint(1) NOT NULL,
`parent` int(10) NOT NULL,
`views` int(5) NOT NULL,
`status` smallint(1) NOT NULL,
PRIMARY KEY (`id`),
KEY `lang` (`lang`,`status`),
KEY `date` (`date`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=47122 ;
as you can see i have two indexes: "lang" and "date"
I have tried some combinations of different indexes and this one has produced me the best results ... unfortunately only on my local computer. On the server i still have bad results. I want to say that the database is the same.
query:
SELECT id FROM news WHERE lang = 'en' AND STATUS =1 ORDER BY DATE DESC LIMIT 0, 10
localhost explain:
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
| 1 | SIMPLE | news | index | lang | date | 3 | NULL | 23 | Using where |
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
server explain:
+----+-------------+-------+------+---------------+--------+---------+-------------+-------+-----------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+------+---------------+--------+---------+-------------+-------+-----------------------------+
| 1 | SIMPLE | news | ref | status | status | 13 | const,const | 15840 | Using where; Using filesort |
+----+-------------+-------+------+---------------+--------+---------+-------------+-------+-----------------------------+
I have looked a lot of other similar topics, but unfortunately i cannot find any solution to work on my server. I will be very glad to here from you some solution with some explanation for that so i can optimize my other queries.
Thanks !
This is your query:
SELECT id
FROM news
WHERE lang = 'en' AND STATUS =1
ORDER BY DATE DESC
LIMIT 0, 10
The best index is one that contains all the fields used in the query (four fields in all). The ordering in the index is by equality conditions in the where clause followed by the order by clause followed by other columns in the select clause.
So, try this index: ndws(leng, status, date, id).
I currently have 2 tables that are used for a select query with a simple join. The first table houses around 6-9 million rows, and this gets used as the join. The primary table is anywhere from 1mil to 300mil rows. However, I notice when I join above 10mil rows on the primary table the select query goes from instant to very slow (3+ seconds and grows).
Here is my table structure and queries.
CREATE TABLE IF NOT EXISTS `links` (
`link_id` int(10) unsigned NOT NULL,
`domain_id` mediumint(7) unsigned NOT NULL,
`parent_id` int(11) unsigned DEFAULT NULL,
`hash` int(10) unsigned NOT NULL,
`url` text NOT NULL,
`type` enum('html','pdf') DEFAULT NULL,
`processed` enum('N','Y') NOT NULL DEFAULT 'N',
UNIQUE KEY `hash` (`hash`),
KEY `idx_processed` (`processed`),
KEY `domain_id` (`domain_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 ROW_FORMAT=COMPACT;
CREATE TABLE IF NOT EXISTS `domains` (
`domain_id` mediumint(7) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(170) NOT NULL,
`blocked` enum('N','Y') NOT NULL DEFAULT 'N',
`count` mediumint(6) NOT NULL DEFAULT '0',
`mcount` mediumint(3) NOT NULL,
PRIMARY KEY (`domain_id`),
KEY `name` (`name`),
KEY `blocked` (`blocked`),
KEY `mcount` (`mcount`),
KEY `count` (`count`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=10834389 ;
Query:
(SELECT link_id, url, hash FROM links, domains WHERE links.domain_id = domains.domain_id and mcount > 1 and processed='N' limit 200)
UNION
(SELECT link_id, url, hash FROM links where processed='N' and type='html' limit 200)
Explain select:
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+--------------+------------+-------+-------------------------+--------------- +---------+---------------------------+---------+-------------+
| 1 | PRIMARY | domains | range | PRIMARY,mcount | mcount | 3 | NULL | 257673 | Using where |
| 1 | PRIMARY | links | ref | idx_processed,domain_id | domain_id | 3 | crawler.domains.domain_id | 1 | Using where |
| 2 | UNION | links | ref | idx_processed | idx_processed | 1 | const | 7090017 | Using where |
| NULL | UNION RESULT | <union1,2> | ALL | NULL | NULL | NULL | NULL | NULL | |
+----+--------------+------------+-------+-------------------------+---------------+---------+---------------------------+---------+-------------+
Right now, I'm trying a partition with 20 partitions on links using domain_id as the key.
Any other options would be greatly appreciated.
A single SELECT statement would replace your entire UNION statement:
SELECT link_id, url, hash
FROM links, domains
WHERE links.domain_id = domains.domain_id
AND mcount > 1
AND processed='N'
AND type='html'
This may not be THE answer you are looking for, but it should help you simplify your question.
When things suddenly slow down you might want to check the size of your indexes (used in the query execution) vs size of various mysql buffers.